Understanding neutron radiography post exam reading viii part 2b of 2a

Understanding Neutron Radiography Reading VIII Part 2bof 2

21st August 2016 Post Exam Reading

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Fusion Reactor Scientists have successfully switched on the world's largest 'Stellarator' fusion reactor. Dubbed Wendelstein 7-X (W7-X), the reactor is designed to contain super-hot plasma for more than 30 minutes at a time

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http://www.dailymail.co.uk/sciencetech/article-3356624/Stellarator-SUCCESS-Strange-twisted-design-finally-make-fusion-power-reality-switched-time.html

Fusion Reactor

Fusion involves placing hydrogen atoms under high heat and pressure until they fuse into helium atoms.

When deuterium and tritium nuclei - which can be found in hydrogen - fuse, they form a helium nucleus, a neutron and a lot of energy. 21D + 31T →42H2+ + n This is down by heating the fuel to temperatures in excess of 150 million °C, forming a hot plasma.

Strong magnetic fields are used to keep the plasma away from the walls so that it doesn't cool down and lost it energy potential.

These are produced by superconducting coils surrounding the vessel, and by an electrical current driven through the plasma.

For energy production. plasma has to be confined for a sufficiently long period for fusion to occur.

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http://www.dailymail.co.uk/sciencetech/article-3356624/Stellarator-SUCCESS-Strange-twisted-design-finally-make-fusion-power-reality-switched-time.html

Fusion Reactor

Fusion involves placing hydrogen atoms under high heat and pressure until they fuse into helium atoms.

When deuterium and tritium nuclei - which can be found in hydrogen - fuse, they form a helium nucleus, a neutron and a lot of energy. 21D + 31T →42H2+ + n This is down by heating the fuel to temperatures in excess of 150 million °C, forming a hot plasma.

Strong magnetic fields are used to keep the plasma away from the walls so that it doesn't cool down and lost it energy potential.

These are produced by superconducting coils surrounding the vessel, and by an electrical current driven through the plasma.

For energy production. plasma has to be confined for a sufficiently long period for fusion to occur.

Charlie Chong/ Fion Zhang

http://www.dailymail.co.uk/sciencetech/article-3356624/Stellarator-SUCCESS-Strange-twisted-design-finally-make-fusion-power-reality-switched-time.html

Fusion Reactor

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Fusion Reactor

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Fusion Reactor

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http://www.popsci.com/science/article/2010-06/deuterium-diy-man-builds-homemade-nuclear-fusion-reactor-brooklyn

Fusion Reactor

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http://www.gizmodo.com.au/2014/01/27-amazing-images-from-the-depths-of-scientific-labs/

The Magical Book of Neutron Radiography

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数字签名者：Charlie Chong DN：cn=Charlie Chong, o=Technology Resources Center, ou=NDE, email=charlieccchong @outlook.com, c=CN 日期：2016.08.23 18:52:43 +08'00' Charlie Chong/ Fion Zhang

ASNT Certification Guide NDT Level III / PdM Level III NR - Neutron Radiographic Testing Length: 4 hours Questions: 135 1. Principles/Theory • Nature of penetrating radiation • Interaction between penetrating radiation and matter • Neutron radiography imaging • Radiometry 2. Equipment/Materials • Sources of neutrons • Radiation detectors • Non-imaging devices

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3. Techniques/Calibrations

• Electron emission radiography

• Blocking and filtering

• Micro-radiography

• Multifilm technique

• Laminography (tomography)

• Enlargement and projection

• Control of diffraction effects

• Stereoradiography

• Panoramic exposures

• Triangulation methods

• Gaging

• Autoradiography

• Real time imaging

• Flash Radiography

• Image analysis techniques

• In-motion radiography • Fluoroscopy

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4. Interpretation/Evaluation • Image-object relationships • Material considerations • Codes, standards, and specifications 5. Procedures • Imaging considerations • Film processing • Viewing of radiographs • Judging radiographic quality 6. Safety and Health • Exposure hazards • Methods of controlling radiation exposure • Operation and emergency procedures Reference Catalog Number NDT Handbook, Third Edition: Volume 4, Radiographic Testing 144 ASM Handbook Vol. 17, NDE and QC 105 Charlie Chong/ Fion Zhang

Fion Zhang at Copenhagen Harbor 21st August 2016

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SME- Subject Matter Expert http://cn.bing.com/videos/search?q=Walter+Lewin&FORM=HDRSC3 https://www.youtube.com/channel/UCiEHVhv0SBMpP75JbzJShqw

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Gamma- Radiography TABLE 1. Characteristics of three isotope sources commonly used for radiography.

Source

T½

Energy

HVL Pb

HVL Fe

Specific Activity

Dose rate*

Co60

5.3 year

1.17, 1.33 MeV

12.5mm

22.1mm

50 Cig-1

1.37011

Cs137

30 years

0.66 MeV

6.4mm

17.2mm

25 Cig-1

0.38184

Ir192

75 days

0.14 ~ 1.2 MeV (Aver. 0.34 MeV)

4.8mm

?

350 Cig-1

0.59163

Th232

Dose rate* Rem/hr at one meter per curie

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0.068376

八千里路云和月

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闭门练功

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http://greekhouseoffonts.com/

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https://independent.academia.edu/CharlieChong1

Whole Chapter 6 Radiation Safety

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PART 1. Management of Radiation Safety

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Introduction There are many considerations involved in setting up and outfitting a safe radiographic facility. Commercial consulting firms specializing in personnel dosimetry and radiation protection may help with this goal. Regardless of who establishes or monitors the program, it is vitally important that radiation exposures to personnel be reduced to as low a level as is practical. To this end, each radiographic facility should appoint a radiation safety officer, who is responsible for systematically assuring management that a safe operation exists. The functions of the radiation safety officer are discussed later in this part.

In the twenty-first century, some publications of the 1970s are still useful to document information in laterpublications. However, all guidelines, standards, regulations and handbooks have a shelf life beyond which some of their information is obsolete. It is the duty of inspectors and safety personnel to become familiar with the literature and refer to up-to-date documents for critical decisions.

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Because of potential changes in safety requirements, radiation safety officers and all personnel active in the field of radiography should consult the most up-to-date publications and regulations before making a determination on the safety of a radiographic facility. Many publications are written specifically to describe in detail the requirements and techniques involved. The following discussion is an overview of radiation safety and personnel protection and does not attempt to duplicate the information available elsewhere — for example, in the works cited in the references and bibliography at the end of this chapter. Unsealed radioactive sources and the associated health protection requirements, internal dosimetry, instrumentation and related subjects are not covered in this chapter. Note also that safety regulations may vary with locality.

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Radiation Safety Inspections and Audits Government Licensing Most manufacturers specify that radiation producing devices should be operated only by qualified personnel. Most states require the registration of radiation machines and provide survey services during compliance audits.

Licenses to possess byproduct materials (radioisotopes other than radium) (?) are issued by the Nuclear Regulatory Commission (NRC) or states operating under its rules (agreement states).

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Radiation Safety Officer Personnel responsible for work with radiation are also responsible for radiation safety. A radiation safety officer (RSO) needs to be appointed if fields may be experienced in excess of 1 mSv (100 mrem) per work week in accessible regions inside or outside externally applied shielding. The radiation safety officer is responsible for: 1. technical assistance in planning and execution of work insofar as radiation safety is concerned, 2. appraisal of safe operation of the radiation source through surveys and personnel monitoring, 3. notification of personnel working around the source of any special hazards, 4. reporting of radiation hazards or unsafe practices to the proper authorities, 5. seeking advice from qualified experts when necessary, 6. keeping records of personnel exposures and area dose levels, 7. keeping informed of any changes in the mode of operation of the source and 8. periodically providing radiation safety training.

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A good radiation safety officer has the confidence and support of company management and the radiography personnel. Fair and honest treatment, knowledge of the regulations and open mindedness to ideas and needs of those involved builds a good working relationship. This relationship helps to ensure that corrective actions are taken, however unsavory 令人讨厌的. The radiation safety officer must have access to any level of management necessary to ensure the compliance with regulations and procedures to provide for a safe work environment.

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Written Procedures All radiographic work must be covered by written procedures that are reviewed and updated annually. The radiation safety officer needs to work with operating personnel and management in preparing these procedures so that adequate safety procedures are integrated with the needs and goals of the workplace environment. The radiation safety officer can recommend approval of a written procedure but only management can approve the procedure with a signature.The level of management required for approval depends on the level of risk for operation. Where first level management is delegated to approve some procedures, a written delegation of authority from top management should be on file in the radiation safety officer’s records.

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Emergencies Written procedures should exist for actions to be taken in case of an emergency. While the radiation safety officer may have considerable authority in a radiation emergency situation, the written procedures should make it clear that management is responsible for assuming the level of risk for any action taken in case of an emergency. The case of a radiographic source that because of mechanical problems cannot be returned to its storage container provides an example. In this situation, all personnel should know from existing general procedures to evacuate to a safe distance or location where a specific, written procedure, even handwritten, can be prepared and approved for restoring the source. In a case where an injured or unconscious person is exposed to a hazardous radiation dose rate, time is very important.

Written procedures prepared in advance with assignments of roles and responsibilities, combined with periodic training and practice scenarios, can facilitate the rapid recovery of an immobile person without unacceptable radiation exposures to recovery personnel.

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Internal Inspections An internal inspection system is essential to maintaining a quality industrial radiography program. Internal inspection programs are mandated by regulations and are vital to ensure safe operations and the welfare of radiography workers as well as of the general public. Required internal inspections consist of semiannual radiographer audits, an annual overview audit of the entire radiation protection program, an annual review of the quality assurance program and a continuous review of the company program to keep personnel exposures as low as reasonably achievable (ALARA).

Audit procedures for gamma radiography or X-radiography are basically the same, just as observations of temporary field sites are conducted in a manner similar to cell or permanent facility audits. These components make up the internal inspection system.

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The single most important part of the internal inspection system is the radiation safety officer. The radiation safety officer should have sufficient experience and expertise to observe radiography operations and immediately recognize infractions 犯规 or violations as well as good practices. The radiation safety officer should be able to make a valid assessment of the conditions observed and provide corrective actions or recommendations to those involved. Any and all discrepancies should immediately be pointed out to the responsible individuals with a followup notification to the appropriate supervision. The radiation safety officer should conduct audits in person and take appropriate actions to stop violations or unsafe practices. Unfortunately some regulations are instituted as a result of the actions of a few individuals.

The integrity of the radiation safety officer and the radiographers are important to a good radiation safety program. A good relationship between regulators and licensees is also important to a quality program. Regulators should not be feared or shunned 躲避: avoidance gives the impression that people have something to hide. A number of factors can affect how an individual reacts to situations.

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Very few people start out with the intention to break the rules. But good intentions, lack of training, lack of proper equipment or misunderstanding of the requirements can result in problems. Many factors can contribute to the situation, such as tight schedules, cost implications and the mental health or morale of the persons involved. Maybe there is a bonus offered to finish the job early. Radiographers that circumvent the regulations or take short cuts around procedural requirements run greater risk of accidents or overexposures than those that continuously operate by the book. Audits are necessary to detect and correct breaches of safety procedure. What makes up an audit or observation varies. Simply questioning a radiography crew can often provide a false idea of how the crew normally operates. An experienced auditor can usually perceive more while approaching a radiography job site and observing the normal work practices than can be obtained by spending eight hours sitting on a job and interviewing radiographers. During that amount of time when the auditor’s presence is not known, work ethics are demonstrated and the real story is told. Followup interviews should be conducted to verify the details that must be noted: serial numbers, calibration dates and items that need to be checked and validated.

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This is not to suggest in any way that observations should be conducted, as some audits are conducted, from a long distance by hidden auditors with binoculars. Audits should be open exchanges of information. All parties involved should be treated with the dignity and respect expected in any business encounter. All involved should participate in a professional manner.

The radiographers should be aware that the sole purpose of the radiation safety officer, observer or auditor at the job site is to validate that the radiography team is operating to the established procedures and within the restraints of governing regulations, not to try to catch the participants committing infractions. Systematic or generic deficiencies should be addressed to appropriate management for long term corrective actions. The audit process should be a positive experience rather than a traumatic 极不愉 快的 one. A more casual, relaxed, audit allows an opportunity to experience the way things are done.

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This is not to suggest in any way that observations should be conducted, as some audits are conducted, from a long distance by hidden auditors with binoculars.

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This is not to suggest in any way that observations should be conducted, as some audits are conducted, from a long distance by hidden auditors with binoculars.

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Careful observation of details, such as radiation levels at the posted boundaries, can be conspicuously determined while approaching the job site.

Proper surveillance techniques, area control procedures and adherence to proper operating procedures should become obvious as the auditor approach the radiography operation. The better the auditor understands operations, the better the ability to identify existing or potential problems. Experience provides a higher potential to ensure the safety of personnel involved as well as the general public. Large scale operations with many radiographers or multiple locations may require assistant radiation safety officers or radiation safety officer delegates to be assigned to provide the support and coverage needed to ensure compliance.

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Temporary Field Sites versus Permanent Facilities for Isotopic Sources At temporary field sites specific restraints apply. Generally each field site operation offers a new challenge. The site should be examined and assessed to determine problems that might arise. Location and overall conditions at the work site affect the operations. Distances to radiation area boundaries need to be calculated and posted as required to prevent unauthorized entry into the radiography area. Conditions may require that nonradiography personnel must work in close proximity to the radiography boundaries. Surveillance is required to maintain control of the established area. Specific transportation requirements and regulations mandate how the radiographic exposure device and equipment are transported to the work location. Radiation surveys must be performed to ensure compliance with established procedural requirements.

Peak readings need to be documented. Emergency procedures and points of contact should be reviewed to afford timely response in the event of an accident or emergency.

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By the nature of the operation, an overexposure or other accident is more likely during a temporary field operation. Permanent facilities are constructed and evaluated to determine restrictions for use. These restrictions allow some relaxation of the requirements associated with temporary field site operations.

If permanent cells are used within the parameters established, radiation levels outside the facility will always be at acceptable limits. The safety inspector must confirm that activities are within the established parameters.

Exposure cells must be outfitted with alarms and warning devices and these devices now require a daily operability check. Accesses to the facility must be locked or guarded while exposures are being completed. In industrial radiography operations, high radiation exists in permanent exposure cells — for example, facilities equipped with cobalt-60 exposure devices of 14 TBq (385 Ci).

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Some permanent facilities also serve as long term storage areas for radiography exposure devices. When established as a storage area, additional radiation surveys and postings are required and should be checked.

When it is necessary to operate an exposure cell outside of the established parameters for use, the cell can be established as a temporary field site.

Additional considerations needed for a temporary site will then apply. If an alarm or warning device malfunctions, a permanent facility may be used as a temporary field site but current regulations must be checked to find out how long.

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Semiannual Isotopic Source Audits Field audits of radiography are required to be conducted semiannually, quarterly in some locations. Every person, radiographer, radiographer’s assistant or radiation safety officer that operates radiography equipment or participates directly in a radiography operation must be observed. A checklist should be used to ensure that each specific point is properly addressed. A regular semiannual inspection should cover the following.

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1. Determine the source and exposure device being used. Verify the serial number of the source and the exposure device.

2. 2. Check that the source is safe from unauthorized removal or tampering.

3. 3. Check the condition of the equipment in use. Are a sufficient number properly functioning, calibrated survey meters available on the job site?

Are the exposure device, control assembly and source guide tubes in good working condition? Does the equipment appear to have received adequate inspection and maintenance for the conditions of use?

4. 4. Check to ensure that the equipment is being operated properly and in accordance with established procedures. Are good collimators and shielding being used? Are practices being followed to keep exposures as low as reasonably achievable? Are trainees and assistants being properly supervised?

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5. Do all persons involved with the operation have required personnel monitoring devices? Is each dosimeter within calibration, not discharged beyond its range? Is a thermoluminescent dosimeter badge or film badge available and being used? Is an alarming rate meter available and within calibration?

6. 6. Ensure that the area is adequately posted in accordance with applicable procedures. Signs must be posted for restricted and high radiation area boundaries.

7. 7. Check to ensure that the high radiation is under constant direct surveillance at all times while the source is exposed. Are adequate controls established to keep unauthorized personnel out of the radiography area?

8. 8. Are procedures being properly followed? Are surveys being taken as required? Do the people involved display adequate competence for the tasks involved?

9. 9. Check the records to ensure that the source use log agrees with the source and equipment in use. Is all required information properly documented? Are the transportation records in order?

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Personnel Certification for Radiation Safety The United States Nuclear Regulatory Commission (NRC) has published rules that govern the use of nuclear, or gamma, radiation in those states that choose to follow federal regulations, the NRC states. In contrast, states that wish to use their own regulations, which must meet or exceed Nuclear Regulatory Commission requirements, are known as agreement states and their regulations are in force for nuclear radiation in those states. Because Xrays (unlike gamma rays) are not generated by nuclear materials, the Nuclear Regulatory Commission does not have jurisdiction over X-ray radiography and each state is responsible for regulating X-radiography. Radiographers working in any state must be aware of who has jurisdiction over radiation safety and must adhere to the requirements that govern in that state. In some instances, large metropolitan areas also have requirements and these must also be met when working in those areas.

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Safety Personnel Certification In May 1997, the Nuclear Regulatory Commission published a rule requiringthat all industrial radiographers using radioactive materials be certified through either an approved independent certifying organization (ICO) or an agreement state program that complied with the criteria in 10CFR [Code of Federal Regulations: Title 10], Part 34, Appendix A.8 The final deadline for compliance was set as July 1999 for Nuclear Regulatory Commission states and as July 2000 for agreement states. The American Society for Nondestructive Testing (ASNT), in an effort to provide a service to industry, developed the American Society for Nondestructive Testing’s Industrial Radiography Radiation Safety Personnel (IRRSP) program, which was sent to the Nuclear Regulatory Commission for review in late 1997. In May 1998, The Nuclear Regulatory Commission formally approved the American Society for Nondestructive Testing as an independent certifying organization and accepted the radioactive materials (RAM) portion of the Industrial Radiography Radiation Safety Personnel examinations.

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The Nuclear Regulatory Commission does not take responsibility for radiation producing machines, such as X-ray machines used in radiographic testing.

Each individual state was responsible for determining their own certification requirements for radiographers using X-radiation.

The agreement states, to minimize duplication and establish uniformity between the States’ certification requirements, formed the Conference for Radiation Control Program Directors (CRCPD). In early 1998, the American Society for Nondestructive Testing asked the Conference for Radiation Control Program Directors to review the Industrial Radiography Radiation Safety Personnel program to determine if it would meet the requirements of the agreement states. In September 2001, after detailed review and some revision of the program, the Conference for Radiation Control Program Directors formally approved the American Society for Nondestructive Testing as an independent certifying organization and recommended acceptance of the radioactive materials examinations and X- ay examinations for use by agreement states. This decision was sent to all agreement states, because each state makes its own decision whether or not to accept recommendations of the Conference for Radiation Control Program Directors.

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Radiographer Certification Radiographers are generally required to carry two types of certification, one based on technical competence and the other based on the knowledge of safety regulations. The requirements listed in commercial codes, standards and specifications are predominantly technical and rely on the contractor (the radiographer’s employer) to ensure that all applicable safety requirements are met. The safety requirements are detailed by the local, state or federal government regulatory agencies that have jurisdiction over radiography in the locale where the work is to be performed. Technical certification is required by the code or standard governing a specific project. The purpose of this certification is to ensure that the radiographer can make proper exposures and accurately interpret radiographs in accordance with the requirements of the governing code or specification. Each code or specification has varying technical requirements and each will specify that a radiographer be certified somehow before working on projects governed by those documents.

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A certified radiographer will be able to produce acceptable radiographs that accurately show that the quality of workmanship required by the designer has been achieved. Safety certification is required by local, state and federal regulatory agencies. Because of the dangers of penetrating radiation, these agencies want to ensure the safety of the general public and require that all radiographers demonstrate their knowledge of safety regulations by successfully completing a safety examination on the type of radiation to be used in the course of their work. To be eligible to sit for these safety examinations, radiographers must be able to show that they have had adequate training and experience in performing radiography.

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Transportation of Radioactive Materials Radioactive material is considered hazardous material. As a result its shipment within the United States iscontrolled by the Department of Transportation (DOT) under the Code of Federal Regulations, Title 49, Subtitle B, Parts 171-177.11 These regulations prescribe the rules and procedures for packaging, marking, labeling, placarding and shipping.

Additional equirements for the international shipment of such materials by air are set forth by the International Air Transport Association (IATA). Except for very minor quantities, use of the Postal Service for transport of radioactive materials is prohibited. Finally the Inter-Governmental Maritime Consultative Organization (IMCO) and the International Atomic Energy Agency (IAEA, an office of the United Nations) represent the collection of nations around the world that regulate the international transport of dangerous goods by sea.

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Disposal The disposal of leaking sources, contaminated equipment or sources decayed below useful levels must be according to the Code of Federal Regulations, Title 10.12 Generally, a commercial radioactive waste disposal service licensed by the Nuclear Regulatory Commission is used for this purpose, either directly by the owner of the source or indirectly by returning the source to the manufacturer.

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Disposal Radioactive Waste

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Radiographer at Works

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Radiographer at Works

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Radiographer at Works

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Experts at Works

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Experts at Works

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Experts at Works

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Experts at Works

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Radioactive Isotope Industrial Radiography

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PART 2. Dose Definitions and Exposure Levels

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Radiation Quantities and Units Radiation is measured by the International System of Units (SI), described elsewhere in this volume. SI units include the Becquerel, Coulomb, Sievert and Gray. The literature for radiation safety also uses older units, such as roentgen, curie, rad and rem. Because of the widespread use of the older units in the United States, especially in regulatory documents dealing with health and safety, the United States Department of Commerce in 1998 accepted these older units with SI.13 All these units are discussed briefly below.

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Rate of Decay. the rate at which a radionuclide decays. In SI, the unit for radioactivity is the becquerel (Bq), one disintegration per second. Because billions of disintegrations are required in a useful source, the multiplier prefix giga- (109) is used and the unit is normally seen as gigabecquerel (GBq). An older unit is the curie (Ci), simply the radiation of 1 g of radium. A curie is equivalent to 37 GBq, that is, to 3.7 × 1010 (37 x 109) disintegrations per second.

Exposure.

Exposure is a measure of X-radiation or gamma radiation based on the ionization produced in air by X-rays or gamma rays. The unit for quantity of electric charge is the coulomb (C), where 1 C = 1 A × 1 s. The original roentgen (R) was the quantity of radiation that would ionize 1 cm3 of air to 1 electrostatic unit (ESU) of charge (where 1 ESU = 3.3356 × 10–10 C) of either sign. A roentgen is equivalent to 258 microcoulombs per kilogram of air (1 R = 258 μC·kg–1 of air). This corresponds to 1.61 × 1015 ion pairs per 1 kg of air, which has then absorbed 8.8 mJ (0.88 rad, where rad is the obsolete unit for radiation absorbed dose, not the SI symbol for radian).

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http://slideplayer.com/slide/1427176

Absorbed Dose.

Absorbed dose is the mean energy imparted to matter (what matter?) by ionizing radiation per unit mass of irradiated materials at the place of interest.

The roentgen (R) was an intensity unit but was not representative of the dose absorbed by material in the radiation field. The radiation absorbed dose (rad) was first created to measure this value and was based on the erg, the energy unit from the old centimeter-gram-second (CGS) system. In the SI system, the unit for radiation dose is the gray (Gy). The gray is useful because it applies to doses absorbed by matter at a particular location. It is expressed in energy units per mass of matter or in joules per kilogram (J·kg–1). The mass is that of the absorbing body. One gray equals 100 rad equals 10 000 ergs per gram (1 Gy = 100 rad = 10 000 erg·g–1).

1 Gy = J·kg–1 1 Gy = 100 rad 1 rad = 100 erg·g–1

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Dose Equivalent.

Dose equivalent H is a quantity used for radiation protection that expresses on a common scale for all irradiation incurred by exposed persons. The SI unit of dose equivalent is the Sievert, equal to 100 rem (1 Sv = 100 rem). The SI system’s unit for the dose absorbed by the human body (formerly rem for roentgen equivalent man; also known as ambient dose equivalent, directional dose equivalent, dose equivalent, equivalent dose and personal dose equivalent) is similar to the gray but includes quality factors dependent on the type of radiation. This absorbed dose has been given the name Sievert (Sv) but its dimensions are the same as the gray (J·kg–1), that is, 1 Sv = 1 J·kg–1.

Keywords: This absorbed dose has been given the name Sievert (Sv) but its dimensions are the same as the gray (J·kg–1), that is, 1 Sv = 1 J·kg–1.

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TABLE 1. Radiation weighting factors.

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a. Value of quality factor at point where dose equivalent is maximum in 300 mm (12 in.) diameter cylinder tissue equivalent phantom.

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a. Value of quality factor at point where dose equivalent is maximum in 300 mm (12 in.) diameter cylinder tissue equivalent phantom.

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Quality Factor. Quality factor15-18 is a modifying factor used in determining the dose equivalent. The quality factor corrects for the dependence ofbiological factors on the energy and type of the radiation. A formerly commonly used term, relative biological effect, is restricted in use to radiobiology. For practical purposes the quality factors in Table 1 are conservative. For example, consider an absorbed dose in the lens of the eye of 1 mGy (0.1 rad) from 2 MeV neutrons. The dose equivalent is: H

= Dose in milligray x Quality Factor = 1 mGy x 10 = 10mSv

H

= Absorbed Dose x Quality Factor

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Compound Units Roentgens could be measured with an ionization chamber that, when placed 1.0 m (39 in.) from the radiation source, provided necessary information — one roentgen per hour at one meter (1 R·h–1 at 1 m), for example. The roentgen per hour (R·h–1) was used to designate the exposure to an ionizing radiation of the stated value.

The SI unit used for this exposure rate is the sievert (Sv), 100 times as large as the compound unit it replaces: 1 Sv·h–1 = 100 R·h–1. The radiation received from 1 R·h–1 appeared equal to about 1 rem, so the relationship is approximated as 1 R·h–1 = 0.01 Gy·h–1 = 10 mGy·h–1. A previously popular unit, roentgen per curie per hour at one meter (R·Ci–1·h–1 at 1 m), is expressed in SI units as millisievert per gigabecquerel per hour at one meter (mSv·GBq–1·h–1 at 1 m), such that 1 mSv·GBq–1·h–1 at 1 m = 3.7 R·Ci–1·h–1 at 1 m. In this relationship, roentgen converts to millisievert on a one-to-ten basis. Exposure charts were often made by using curie minutes at a squared distance from source to sensor in inches. This was written Ci·min·in.–2.

Exposure charts made in SI use gigabecquerel minutes for a squared distance from source to sensor in centimeters, where 1 Ci·min·in.–2 = 50 GBq·min·cm–2.

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Permissible Doses Concept of ALARA (As Low As Reasonably Achievable) All persons should make every reasonable effort to maintain radiation exposures as low as is reasonably achievable, taking into account the state of technology and the economics of improvements in relation to benefits to the public health and safety. In this sense, the term permissible dose is an administrative term mainly for planning purposes.

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TABLE 2. Maximum permissible dose per quarter of calendar year (3 mo) for whole body irradiation.

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Prospective Annual Limit for Occupationally Exposed Personnel The maximum permissible prospective dose equivalent for whole body irradiation is 50 mSv (5 rem) in any one year.

The Nuclear Regulatory Commission has further restricted for its licensees the rate at which this planned annual dose may be received by averaging over calendar quarters rather than calendar years. This maximum dose and limits for other parts of the body are summarized in Table 2

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Permissible Levels of Radiation in Unrestricted Areas Non occupationally exposed personnel or all personnel in unrestricted areas (see below) shall not receive more than 1.0 mSv (0.1 rem) (100 mrem) to the whole body in any period of one calendar year.

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Restricted Areas A restricted area needs to be established where either 1. a dose in excess of 20 ÎźSv (2 mrem) can be received in any 1 h or 2. a dose in excess of 1.00mSv (100 mrem) can be received in a calendar year.

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Exposure of Minors An individual under 18 years of age must not be exposed to greater than 10 percent of the limits for occupationally exposed workers, that is, 10 percent of 12 mSv (1.25 rem) per quarter to the whole body and similarly for the hands, forearms, feet, ankles and skin of the whole body.

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0 1 1/ Charlie Chong/ Fion Zhang

Exposure of Minors An individual under 18 years of age must not be exposed to greater than 10 percent of the limits for occupationally exposed workers, that is, 10 percent of 12 mSv (1.25 rem) per quarter to the whole body and similarly for the hands, forearms, feet, ankles and skin of the whole body.

0 1 1/ Charlie Chong/ Fion Zhang

Exposure of Minors An individual under 18 years of age must not be exposed to greater than 10 percent of the limits for occupationally exposed workers, that is, 10 percent of 12 mSv (1.25 rem) per quarter to the whole body and similarly for the hands, forearms, feet, ankles and skin of the whole body.

0 1 1/ Charlie Chong/ Fion Zhang

Exposure of Minors An individual under 18 years of age must not be exposed to greater than 10 percent of the limits for occupationally exposed workers, that is, 10 percent of 12 mSv (1.25 rem) per quarter to the whole body and similarly for the hands, forearms, feet, ankles and skin of the whole body.

0 1 1/ Charlie Chong/ Fion Zhang

Exposure of Minors An individual under 18 years of age must not be exposed to greater than 10 percent of the limits for occupationally exposed workers, that is, 10 percent of 12 mSv (1.25 rem) per quarter to the whole body and similarly for the hands, forearms, feet, ankles and skin of the whole body.

0 1 1/ Charlie Chong/ Fion Zhang

Exposure of Minors An individual under 18 years of age must not be exposed to greater than 10 percent of the limits for occupationally exposed workers, that is, 10 percent of 12 mSv (1.25 rem) per quarter to the whole body and similarly for the hands, forearms, feet, ankles and skin of the whole body.

0 1 1/ Charlie Chong/ Fion Zhang

Exposure of Minors An individual under 18 years of age must not be exposed to greater than 10 percent of the limits for occupationally exposed workers, that is, 10 percent of 12 mSv (1.25 rem) per quarter to the whole body and similarly for the hands, forearms, feet, ankles and skin of the whole body.

0 1 1/ Charlie Chong/ Fion Zhang

Exposure of Minors An individual under 18 years of age must not be exposed to greater than 10 percent of the limits for occupationally exposed workers, that is, 10 percent of 12 mSv (1.25 rem) per quarter to the whole body and similarly for the hands, forearms, feet, ankles and skin of the whole body.

0 1 1/ Charlie Chong/ Fion Zhang

Exposure of Females During the entire nine months of gestation the maximum permissible dose equivalent to the fetus from occupational exposure of the declared pregnant woman should not exceed 5 mSv (0.5 rem) evenly distributed over the entire pregnancy.

0 1 1/ Charlie Chong/ Fion Zhang

Exposure of Females During the entire nine months of gestation the maximum permissible dose equivalent to the fetus from occupational exposure of the declared pregnant woman should not exceed 5 mSv (0.5 rem) evenly distributed over the entire pregnancy.

0 1 1/ Charlie Chong/ Fion Zhang

Subpart D--Radiation Dose Limits for Individual Members of the Public Source: 56 FR 23398, May 21, 1991, unless otherwise noted. ยง 20.1301 Dose limits for individual members of the public. (a) Each licensee shall conduct operations so that (1) The total effective dose equivalent to individual members of the public from the licensed operation does not exceed 0.1 rem (1 mSv) in a year, exclusive of the dose contributions from background radiation, from any administration the individual has received, from exposure to individuals administered radioactive material and released under ยง 35.75, from voluntary participation in medical research programs, and from the licensee's disposal of radioactive material into sanitary sewerage in accordance with ยง 20.2003, and (2) The dose in any unrestricted area from external sources, exclusive of the dose contributions from patients administered radioactive material and released in accordance with ยง 35.75, does not exceed 0.002 rem (0.02 millisievert) in any one hour.

0 5 1/ Charlie Chong/ Fion Zhang

http://www.nrc.gov/reading-rm/doc-collections/cfr/part020/part020-1301.html

Subpart D--Radiation Dose Limits for Individual Members of the Public Source: 56 FR 23398, May 21, 1991, unless otherwise noted. ยง 20.1301 Dose limits for individual members of the public. (a) Each licensee shall conduct operations so that (1) The total effective dose equivalent to individual members of the public from the licensed operation does not exceed 0.1 rem (1 mSv) in a year, exclusive of the dose contributions from background radiation, from any administration the individual has received, from exposure to individuals administered radioactive material and released under ยง 35.75, from voluntary participation in medical research programs, and from the licensee's disposal of radioactive material into sanitary sewerage in accordance with ยง 20.2003, and (2) The dose in any unrestricted area from external sources, exclusive of the dose contributions from patients administered radioactive material and released in accordance with ยง 35.75, does not exceed 0.002 rem (0.02 0 5 millisievert) in any one hour. /

1

Charlie Chong/ Fion Zhang

http://www.nrc.gov/reading-rm/doc-collections/cfr/part020/part020-1301.html

Exposure of Females During the entire nine months of gestation the maximum permissible dose equivalent to the fetus from occupational exposure of the declared pregnant woman should not exceed 5 mSv (0.5 rem) evenly distributed over the entire pregnancy.

0 1 1/ Charlie Chong/ Fion Zhang

Exposure of Females During the entire nine months of gestation the maximum permissible dose equivalent to the fetus from occupational exposure of the declared pregnant woman should not exceed 5 mSv (0.5 rem) evenly distributed over the entire pregnancy.

0 1 1/ Charlie Chong/ Fion Zhang

Exposure of Females During the entire nine months of gestation the maximum permissible dose equivalent to the fetus from occupational exposure of the declared pregnant woman should not exceed 5 mSv (0.5 rem) evenly distributed over the entire pregnancy.

Charlie Chong/ Fion Zhang

Occupational pregnant woman should not exceed 5 mSv (0.5 rem) evenly distributed over the entire pregnancy.

An individual under 18 years of age must not be exposed to greater than 10 % of the limits for occupationally exposed workers, that is, 10 percent of 12 mSv (1.25 rem) per quarter to the whole body and similarly for the hands, forearms, feet, ankles and skin of the whole body.

Annual Limit for Non-Occupationally Exposed Personnel- Adult Female?

0.5R/y

Charlie Chong/ Fion Zhang

0 5 1/

ยง 20.1301 Dose limits for individual members of the public. (a) Each licensee shall conduct operations so that (1) The total effective dose equivalent to individual members of the public from the licensed operation does not exceed 0.1 rem (1 mSv) in a year, exclusive of the dose contributions from background radiation, from any administration the individual has received, from exposure to individuals administered radioactive material and released under ยง 35.75, from voluntary participation in medical research programs, and from the licensee's disposal of radioactive material into sanitary sewerage in accordance with ยง 20.2003, and

0 5 1/ Charlie Chong/ Fion Zhang

http://www.nrc.gov/reading-rm/doc-collections/cfr/part020/part020-1301.html

ยง 20.1301 Dose limits for individual members of the public. (a) Each licensee shall conduct operations so that (1) The total effective dose equivalent to individual members of the public from the licensed operation does not exceed 0.1 rem (1 mSv) in a year, exclusive of the dose contributions from background radiation, from any administration the individual has received, from exposure to individuals administered radioactive material and released under ยง 35.75, from voluntary participation in medical research programs, and from the licensee's disposal of radioactive material into sanitary sewerage in accordance with ยง 20.2003, and

0 5 1/ Charlie Chong/ Fion Zhang

http://www.nrc.gov/reading-rm/doc-collections/cfr/part020/part020-1301.html

Public exposure: The total effective dose equivalent to individual members of the public from the licensed operation does not exceed 0.1 rem (1 mSv) in a year http://www.nrc.gov/reading-rm/doc-collections/cfr/part020/part020-1301.html

Exposure of Minors: An individual under 18 years of age must not be exposed to greater than 10 percent of the limits for occupationally exposed workers, that is, 10 percent of 12 mSv (1.25 rem) per quarter to the whole body and similarly for the hands, forearms, feet, ankles and skin of the whole body.

ASNT Handbook Volume 4, Chapter 6 Part 2

Pregnant Women: Exposure of Females During the entire nine months of gestation the maximum permissible dose equivalent to the fetus from occupational exposure of the declared pregnant woman should not exceed 5 mSv (0.5 rem) evenly distributed over the entire pregnancy.

ASNT Handbook Volume 4, Chapter 6 Part 2

Charlie Chong/ Fion Zhang

Public exposure: The total effective dose equivalent to individual members of the public from the licensed operation does not exceed 0.1 rem (1 mSv) in a year

0 5 1/

http://www.nrc.gov/reading-rm/doc-collections/cfr/part020/part020-1301.html

Exposure of Minors: An individual under 18 years of age must not be exposed to greater than 10 percent of the limits for occupationally exposed workers, that is, 10 percent of 12 mSv (1.25 rem) per quarter to the whole body and similarly for the hands, forearms, feet, ankles and skin of the whole body.

0 ASNT Handbook Volume 4, Chapter 6 Part 2

1 / 1

Pregnant Women: Exposure of Females During the entire nine months of gestation the maximum permissible dose equivalent to the fetus from occupational exposure of the declared pregnant woman should not exceed 5 mSv (0.5 rem) evenly distributed over the entire pregnancy.

ASNT Handbook Volume 4, Chapter 6 Part 2

Charlie Chong/ Fion Zhang

0 1 1/

Discussion What is the;  Prospective Annual Limit for Occupationally Exposed Personnel?  Annual Limit for Non-Occupationally Exposed Personnel- Adult Male?  Annual Limit for Non-Occupationally Exposed Personnel- Adult Female?  Annual Limit for Minor?  Annual Limit for Pregnant Women?

Charlie Chong/ Fion Zhang

Discussion What is the;  Prospective Annual Limit for Occupationally Exposed Personnel?

5R/yr  Annual Limit for Non-Occupationally Exposed Personnel- Adult Male?

0.5R/y  Annual Limit for Non-Occupationally Exposed Personnel- Adult Female?

0.5R/y  Annual Limit for Minor?

0.5R/y without differentiating parts of body  Annual Limit for Pregnant Women?

0.5R/y during whole period of gestation (occupational) ?? R/y during whole period of gestation (non-occupational)

Charlie Chong/ Fion Zhang

Prospective Annual Limit for Occupationally Exposed Personnel The maximum permissible prospective dose equivalent for whole body irradiation is 50 mSv (5 rem) in any one year.15 The Nuclear Regulatory Commission19 has further restricted for its licensees the rate at which this planned annual dose may be received by averaging over calendar quarters rather than calendar years. This maximum dose and limits for other parts of the body are summarized in Table 2.

Charlie Chong/ Fion Zhang

PART 3. Radiation Protection Measurements

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Personnel Dosimetry Requirements Personnel monitoring must be performed on all occupationally exposed persons who may receive in a calendar quarter more than one fourth of the applicable doses in Table 2.

Occasional visitors to restricted areas, including messengers, servicemen and deliverymen, can be regarded as non-occupationally exposed persons who do not need to be provided personnel monitors when it is improbable that they would receive in one year a dose equivalent exceeding the nonoccupational limit of 5 mSv (0.5 rem). Long term visitors in an installation should be regarded as occupationally exposed if they are likely to receive a dose equivalent greater than 5 mSv (0.5 rem) per year.

Keywords: â– one year a dose equivalent exceeding the non-occupational limit of 5 mSv (0.5 rem). (counts in quarterly manners)

Charlie Chong/ Fion Zhang

X-Rays, Gamma Rays and Electrons For radiation protection measurement, the choice lies among ionization chambers, film badges, photoluminescent glasses and thermoluminescent dosimeters. (These and other dosimetric technologies are discussed in the chapter on radiation measurement.) â– Ionization Chambers. The principal advantages of ionization chambers (Fig. 1), particularly those of the self-reading type, are the simplicity and speed with which readings are made. They are useful, therefore, particularly for monitoring exposures during non routine operations or during transient conditions or for monitoring short term visitors to an installation. Chambers should be tested for leakage periodically and those that leak more than a few percent of full scale over the period of use should be removed from service.

Most of these ionization chambers are small, about the size of a pencil, and are charged on a separate device. They read from a few hundredths to a few sievert (a few tens to a few hundred milliroentgen) of exposure.

Charlie Chong/ Fion Zhang

FIGURE 1. Radiation survey meter incorporates air filled ionization chamber vented to atmosphere, with five selectable linear ranges: • • • • •

0 to 50 μSv·h–1 (0 to 5 mR·h–1), 0 to 500 μSv·h–1 (0 to 50 mR·h–1), 0 to 5 mSv·h–1 (0 to 500 mR·h–1), 0 to 50 mSv·h–1 (0 to 5 R·h–1), 0 to 500 mSv·h–1 (0 to 50 R·h–1).

Charlie Chong/ Fion Zhang

Air filled ionization chamber

Charlie Chong/ Fion Zhang

Air filled ionization chamber

Charlie Chong/ Fion Zhang

https://www.orau.org/PTP/collection/radiac/IM156.htm

Air filled ionization chamber IM-156/PD Ion Chamber Survey Meter (ca. 1960) This example of the IM-156/PD was manufactured by Technical Associates of Burbank California. It is obviously the military version of the Juno, but I have not been able to locate any specific references regarding the IM-156/PD. The above photo shows the bottom of the case with the gamma and beta shields partially covering the window opening. The window itself has been broken and is not present.

Although the IM-156/PD can respond to alphas, betas and gamma rays, its response is only calibrated for the latter.

With the window uncovered, the instrument would respond to alpha particles, beta particles and gamma rays. With the beta shield (it actually screens out the alpha particles) in place, the instrument responds to betas and gamma rays. With the gamma shield (it actually screens out beta particles) in place, the instrument only responds to gamma rays.

Charlie Chong/ Fion Zhang

https://www.orau.org/PTP/collection/radiac/IM156.htm

Air filled ionization chamber

Charlie Chong/ Fion Zhang

https://www.orau.org/PTP/collection/radiac/IM156.htm

Air filled ionization chamber

Charlie Chong/ Fion Zhang

ionization chamber

Charlie Chong/ Fion Zhang

ionization chamber- DIY

Charlie Chong/ Fion Zhang

http://www.instructables.com/id/ionization-chamber-made-of-aluminum-can/

DIY Geiger Muller Counter

Charlie Chong/ Fion Zhang

http://www.instructables.com/id/Homemade-Geiger-Counter/

DIY Geiger Muller Counter

Charlie Chong/ Fion Zhang

http://www.instructables.com/id/Homemade-Geiger-Counter/

■ Film Badges. Small badges containing special X-ray films are popular personnel dosimeters (Fig. 2a). The sensitivity of available emulsions is sufficient to detect about 2.6 μC·kg–1 (10 mR) of cobalt-60 gamma radiation and about 0.8 μC·kg–1 (a few mR) of 100 keV X-rays. A useful range is from about 0.8 μC·kg–1 (a few mR) to 500 mC·kg–1 (2 kR) can be covered by two commonly available films or two emulsions of different sensitivity on one film base. For energies below 200 keV, film over responds where, for example, the photographic density per roentgen at 40 keV is about 20 times higher than for 1 MeV photons. Metallic filters covering portions of the film provide additional readings that help determine the incident radiation energy and afford a means of computing a dose from appropriate calibration curves.

Film has several undesirable characteristics. Fogging may result from mechanical pressure, elevated temperatures or exposure to light. Fading of the latent image may result in decreased sensitivity but may be minimized by special packaging to exclude moisture and by storage in a refrigerator or freezer before distribution. Film dosimeters also exhibit directional dependence, particularly for the densities recorded behind metal filters.

Charlie Chong/ Fion Zhang

Film Badge

Charlie Chong/ Fion Zhang

FIGURE 2. Clip-on personal radiation dosimeters: (a) film badges; (b) thermoluminescent dosimeters (TLDs).

Charlie Chong/ Fion Zhang

Ionization Chamber - DIY

http://www.techlib.com/science/ionpage2.html Charlie Chong/ Fion Zhang

■ Photoluminescent Glasses. Silver activated metaphosphate glasses, when exposed to ionizing radiation, accumulate fluorescent centers that emit visible light when the glass is irradiated with ultraviolet light. The intensity of the light is proportional to radiation exposure up to 250 mC·kg–1 (1000 R) or more. Glass dosimeters exhibit energy dependence below 200 keV and are also subject to fading. They are useful down to only 250 μC·kg–1 (1 R).

Charlie Chong/ Fion Zhang

â– Photoluminescent Glasses

Charlie Chong/ Fion Zhang

■ Thermoluminescence. A common technique of personal radiation exposure measurement is thermoluminescent dosimetry (Fig. 2b). The desirable characteristics of thermoluminescent dosimeters (TLDs) include their wide linear range; short readout time; Relative insensitivity to field conditions of heat, light and humidity; reusability; and for some phosphors, energy independence. Response is rate independent up to 1 GSv·s–1 (100 GR·s–1), which can be useful in flash X-ray radiographic installations. Very small thermoluminescent dosimeters can be used to measure exposure to specific parts of the body. They probably represent the technique of choice for measurement of finger, hand or eye dose. They have a useful range down to 1 μC·kg–1 (several mR) for lithium fluoride and even lower for more exotic thermoluminescent dosimetric materials.

■ Others. Electronic dosimeters and hybrid technologies are also available.

Charlie Chong/ Fion Zhang

â– Thermoluminescence TLD

Charlie Chong/ Fion Zhang

â– Thermoluminescence TLD

Charlie Chong/ Fion Zhang

Neutrons Detections For neutron fields the practical devices are: â– nuclear track film, â– thermoluminescent dosimeters containing lithium-6 fluoride and â– fission track counting systems.

The nuclear track films do not respond to neutrons below 0.5 MeV in energy; in practice, a substantial fraction of the neutrons may be below this energy.

Track counting is a relatively insensitive technique of neutron dosimetry. For low doses, counting of a statistically significant number of tracks is too time consuming to be warranted. On the other hand, at high doses it is difficult to distinguish tracks from one another so that they can be counted. Fading occurs and, as a result, short tracks may disappear. For these reasons, nuclear track film is more useful in demonstrating that large neutron doses have not been received than in measuring actual low doses.

Charlie Chong/ Fion Zhang

Nuclear Track (Particle Tracks)

Charlie Chong/ Fion Zhang

Nuclear Track (Particle Tracks)

Charlie Chong/ Fion Zhang

Nuclear Track (Particle Tracks)

Charlie Chong/ Fion Zhang

Nuclear Track (Particle Tracks)

Charlie Chong/ Fion Zhang

The lithium-6 fluoride and fission track counting systems do not suffer from these disadvantages and will provide measurements at permissible dose levels. These techniques are sensitive down to doses of about 30 or 40 μGy (3 or 4 mrad) and down to thermal neutron energies. Boron trifluoride neutron radiation detector tubes provide high gamma rejection up to about 5 Sv·h–1 (500 R·h–1) and detect neutrons with energies from thermal to about 10 MeV (Fig. 3).23 Other means of neutron dosimetry, including ion chambers, have been investigated or developed.23-25

Charlie Chong/ Fion Zhang

Fission Track (Fragments Track?)

Charlie Chong/ Fion Zhang

Fission Track (Fragments Track?)

Charlie Chong/ Fion Zhang

http://www.uib.no/node/57057

Fission Track (Fragments Track?)

Charlie Chong/ Fion Zhang

http://www2.le.ac.uk/research/festival/meet/geosciences/szameitat/thermochronology

Fission Track (Fragments Track?)

Charlie Chong/ Fion Zhang

http://geoinfo.nmt.edu/labs/aft/home.html

Fission Track (Fragments Track?)

Charlie Chong/ Fion Zhang

http://minerva.union.edu/garverj/FT/FThome.html

Radiation Detection and Measurement In an area survey, measurements are made of radiation fields to provide a basis for estimating the dose equivalents that persons may receive. Changes in operating conditions (such as beam orientations and source outputs) can cause changes both in field intensity and pattern. The number of measurements depends on how much the radiation field varies in space and time and on how much people move about in the field. Measurements made at points of likely personnel occupancy under the different operating conditions are usually sufficient to estimate dose equivalent adequately for protection purposes. Detection instruments are used in radiation surveys and area monitoring to warn of the existence of radiation or radiation hazard and, as distinct from measuring instruments, usually indicate count rate rather than dose rate or exposure rate. They should be used only to indicate the existence of radiation.

Charlie Chong/ Fion Zhang

Measurement At points of particular interest, individual determinations of dose or exposure rate should be made with calibrated measuring instruments. Dose integrating devices (dosimeters) may be mounted at points of interest and left for an extended period of time to improve the accuracy of the measurement.

Information concerning the dimensions, dose rate and location of primary beams of radiation in relation to the source is important in determining direct external exposure from the beam and the adequacy of protective measures.

The dose or exposure rates within the beam at specific distance from the source should be measured and compared with expected values.

Measurements close to radiation sources of small dimensions or of radiation transmitted through holes or cracks in shielding require special attention. The general location of discontinuities in shielding should be determined by scanning with sensitive detection instruments. More precise delineation of the size and configuration of the discontinuities can be obtained by using photographic film or fluorescent screens for X-ray, gamma ray or electron leakage. Measurements may then be made in any of three ways:

Charlie Chong/ Fion Zhang

1. Film may be used at the point of interest, provided it has been properly calibrated for the types and energies of the radiations present.

2. An instrument may be used that has a detector volume small enough to ensure that the radiation field throughout the sensitive volume is substantially uniform.

3. An instrument with a large sensitive volume may be used, if an appropriate correction factor is applied. Only when Achamber is larger than Abeam, multiply the reading by the ratio of the instrument chamber cross section area to the beam cross section area:

Reading x Achamber/Abeam = Corrected reading

Charlie Chong/ Fion Zhang

Choice of Instruments The following general properties should be considered. â– Energy Response. If the energy spectrum of the radiation field differs significantly from that of the calibration field, a correction may be necessary. â– Directional Response. If the directions from which the radiations arrive at the instrument differ significantly from those in the calibration field, correction may be necessary.

If the dose equivalents being determined are small in comparison to permissible doses, large errors are acceptable and correction may not be necessary.

Charlie Chong/ Fion Zhang

â– Rate Response.

- Instruments that measure dose or exposure are called integrating instruments; - those that measure dose rate or exposure rate are called rate instruments or rate meters.

If the dose rate or exposure rate differs significantly from that in the calibration field, correction may be necessary. Ordinarily, an integrating instrument should be used only within the rate ranges for which the reading is independent of the rate. Rate instruments, similarly, should be used only within the rate ranges in which the reading is proportional to the rate. A few instruments will become saturated at very high rates; that is, they will cease to function and the reading will drop to zero or close to zero. It is particularly necessary to know the rate response of instruments to be used near machines that produce radiation in short pulses. Rate instruments used near repetitively pulsed machines need only to indicate the average rate for radiation protection purposes.

Charlie Chong/ Fion Zhang

FIGURE 3. Boron trifluoride neutron radiation detector tube provides high gamma rejection up to about 5 Sv ·h–1 (500 R·h–1) and detects neutrons with energies from thermal to about 10 MeV.

http://iccinfocentre.com/backupBdD/ionization-chamber

Charlie Chong/ Fion Zhang

Charlie Chong/ Fion Zhang

â– Mixed Field Response. Because some radiations (such as neutrons) have higher quality factors than others, mixed field monitoring is necessary. This can be done either by using two instruments that are each sensitive to only one radiation or by using two instruments that are sensitive to both but to a different extent. â– Unwanted Response. Interference by energy forms that an instrument is not supposed to measure can be a problem.Response to heat, light, radiofrequency radiations and mechanical shock are examples.

Charlie Chong/ Fion Zhang

Radiofrequency Radiations "Radiofrequency (or RF) Radiation" refers to electromagnetic fields with frequencies between 300 kHz and 300 MHz, while "Microwave (or MW) Radiation" covers fields from 300 MHz to 300 GHz. Since they have similar characteristics, RF and MW radiation are usually treated together. As well, the lower-frequency boundary of RF radiation is often extended to 10 kHz, or even to 3 kHz, in order to include emissions from commonly used devices.

Charlie Chong/ Fion Zhang

http://www.fss.txstate.edu/ehsrm/safetymanual/radiation/rfrad.html

Charlie Chong/ Fion Zhang

http://www.fss.txstate.edu/ehsrm/safetymanual/radiation/rfrad.html

Electromagnetic Spectrum RF radiation is produced by devices such as radio and TV transmitters, induction heaters, and dielectric heaters (also known as RF sealers). MW radiation is produced by microwave ovens, parabolic (dish) antennas, radar devices, and diathermy applicators. See Table I, "Sources of RF/MW Radiation," for more examples.

Federal legislation requires that microwave ovens be constructed to meet stringent microwave leakage limits and to have safety interlocks. When these interlocks are defeated, for example, during repair work, there is a risk of overexposure to microwave radiation.

This guide gives advice on preventing overexposure to RF/MW radiation in the workplace. However, this guide cannot cover all possible situations.

The requirements set out in the Occupational Health and Safety Act must be complied with, and they should be referred to when this guideline is used.

Charlie Chong/ Fion Zhang

http://www.fss.txstate.edu/ehsrm/safetymanual/radiation/rfrad.html

Health Hazards  









The nature and the degree of the health effects of overexposure to RF/MW fields depend on the frequency and intensity of the fields, the duration of exposure, the distance from the source, any shielding that may be used, and other factors.

The main effect of exposure to RF/MW fields is heating of body tissues as energy from the fields is absorbed by the body. Prolonged exposure to strong RF/MW fields may increase the body temperature, producing symptoms similar to those of physical activity. In extreme cases, or when exposed to other sources of heat at the same time, the body's cooling system may be unable to cope with the heat load, leading to heat exhaustion and heat stroke.

Localized heating, or "hot spots," may lead to heat damage and burns to internal tissues. Hot spots can be caused by non-uniform fields, by reflection and refraction of RF/MW fields inside the body, or by the interaction of the fields with metallic implants, for example, cardiac pacemakers or aneurism clips. There is a higher risk of heat damage with organs which have poor temperature control, such as the lens of the eye and the testes.

Other hazards include contact shocks and RF burns. These can result from the electric currents which flow between a conducting object and a person who comes into contact with it while they are exposed to RF fields. (These effects should not be confused with shocks from static electricity.)

Some laboratory studies have reported biological effects from RF/MW radiation at field levels which are too low to cause tissue heating. To date, these non-thermal effects are not known to result in health hazards. Although we are constantly exposed to weak RF fields from radio and television broadcasting, no health risks have been identified from this low-level exposure.

Recent reports suggesting a relationship between either cellular telephone or traffic radar use and cancer have not been substantiated.

Charlie Chong/ Fion Zhang

http://www.fss.txstate.edu/ehsrm/safetymanual/radiation/rfrad.html

â– Fail Safe Provision. To avoid unknowingly exposing personnel to radiation, malfunctions of an instrument should be readily recognizable or should always result in readings that are too high. â– Precision and Accuracy. Typically, precision of a few percent should be obtained on successive readings with the same survey instrument. At the level of a maximum permissible dose a measurement accuracy specified by regulations should be achieved. At levels less than 0.25 the maximum permissible dose a lower level of accuracy (say, a factor of 2) is acceptable.

Charlie Chong/ Fion Zhang

â– Calibration. Instruments used for radiation protection are not absolute instruments; that is, they require calibration in a known radiation field or comparison with instruments whose response is known. Many users of radiation protection instruments must rely on the manufacturer to calibrate their instruments properly. Users should arrange a reproducible field in which the instruments are placed and read frequently at least semianually. The possibility of reading error due to imprecision is minimized by computing the mean of several readings. If changes in the mean reading are detected, the instruments should be recalibrated promptly.

Charlie Chong/ Fion Zhang

■Time Constant. An important characteristic of a rate instrument is the time constant, an indication of the time necessary for the instrument to attain a constant reading when suddenly placed in a constant radiation field. Time constants are generally given as the time required to arrive at 1– e–1 (that is, 0.63) of the final reading. Typical time constants of good rate meters are 1 s or less. The response time of a rate instrument is defined as the time necessary for it to reach 90 percent of full response. It is equal to 2.3 time constants.

Charlie Chong/ Fion Zhang

Radiation Surveying and Area Monitoring Various technologies for radiation surveying and area monitoring are available. The following can be used for sealed gamma ray sources and forsources of X-rays. (More information on these technologies can be found in the chapter on radiation measurement.)

Charlie Chong/ Fion Zhang

■ Ionization Chambers. Many gamma ray and X-ray exposure rate measurements are made with portable ionization chambers (Fig. 1).

Ionization chambers with separate readers are useful for measuring either very high or very low exposure rates. Ion chambers made of plastic or other low atomic number materials usually give exposure readings independent of photon energy down to 50 keV. Ionization chambers are available for exposure rates to over 20 Sv·h–1 (3 or 4 kR·h–1).

■ Geiger-Müller Counters. The dead time in geiger-müller counters (Fig. 4) sets a limit to their count rate that, in turn, limits their use to exposure rates up to about 0.03 nSv (a few μR·h–1). The counters respond to the number of ionizing events within them independent of energy and thus do not yield equal count rates for equal exposure rates of different energies. Geiger-müller counters are better suited for radiation detection than for measurement.

Charlie Chong/ Fion Zhang

■ Geiger-Müller Counters. The dead time in geiger-müller counters (Fig. 4) sets a limit to their count rate that, in turn, limits their use to exposure rates up to about 0.03 nSv (a few μR·h–1). The

counters respond to the number of ionizing events within them independent of energy and thus do not yield equal count rates for equal exposure rates of different energies. Geiger-müller counters are better suited for radiation detection than for measurement.

Charlie Chong/ Fion Zhang

■ Scintillation Instruments. Scintillation devices (Fig. 5) also have count rate limitations because of the duration of the light flashes but can count much faster than geiger-müller counters. In the same exposure field, scintillation count rates are higher than geiger-müller count rates, so scintillation counters are useful for locating weak X-ray and gamma ray fields.

Charlie Chong/ Fion Zhang

FIGURE 4. Gamma and X-radiation sensing devices incorporating Geiger Muller tubes: a. survey meter for range selectable from 0 to 20 mSv·h–1 (0 to 2 R·h–1) and automatic aural alarm over 2.5 mSv·h–1 (250 mR·h–1); b. survey meter with on/off switch for aural monitoring; c. for high noise areas, personal rate alarm with flashing light and optional earplug for aural alarm; d. area monitor with standard 20 μSv·h–1 (2 mR·h–1) trip point, audio piezo alert and large red strobe warning light; e. visual alarm for gamma and X- ays from 80 keV to 1.5 MeV and adjustable alarm threshold.

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a. survey meter for range selectable from 0 to 20 mSv·h–1 (0 to 2 R·h–1) and automatic aural alarm over 2.5 mSv·h–1 (250 mR·h–1);

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Geiger Muller

b. survey meter with on/off switch for aural monitoring;

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Geiger Muller

c. for high noise areas, personal rate alarm with flashing light and optional earplug for aural alarm;

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Geiger Muller

d. area monitor with standard 20 μSv·h–1 (2 mR·h–1) trip point, audio piezo alert and large red strobe warning light;

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Geiger Muller

e. visual alarm for gamma and X- ays from 80 keV to 1.5 MeV and adjustable alarm threshold.

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Geiger Muller

FIGURE 5. Radiation detector with scintillation counter measurement of low energy gamma radiation.

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Instrument Calibration The National Institute of Standards and Technology (NIST) is the point of record for reference standards. Laboratories calibrate according to the National Institute of Standards and Technology. Laboratory standard instruments for measuring exposure from photons of higher energies from 1 to 1000 mSv (0.1 to 100 R) or exposure rate from 0.1 to 150 mSv·min–1 (0.01 to 15 R·min–1) can be calibrated by the National Institute of Standards and Technology by comparison with either cesium-137 or cobalt-60 calibrated sources. These laboratory standard instruments or secondary standards may then be used to calibrate radiation protection survey instruments by comparison in radiation fields of similar quality. Consideration must be given to beam width, uniformity of radiation over the calibration area and changes in radiation quality caused by scattered radiation. Neutron instrument calibration can be afforded by exposure to fields from National Institute of Standards and Technology calibrated neutron sources. One type of such a source is made by mixing a radionuclide such as plutonium, polonium or radium with a material such as beryllium or boron. The neutrons are produced in (α, n) reactions in the latter materials. Radium sources are difficult to use because they also emit intense gamma radiation.

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Leak Testing of Isotope Sealed Sources All sealed sources must be tested for leakage of radioactive material before initial use, at intervals not exceeding six months, whenever damage or deterioration of the capsule or seal is suspected or when contamination of handling or storage equipment is detected. The leak test should be capable of detecting the presence of 185 Bq (5 nCi) of removable activity from the source. Sources that are in the United States and that are leaking greater than 185 Bq (5 nCi) of removable activity, based on the tests described below, should be reported to the Nuclear Regulatory Commission within five days.

Records of leak test results should be specific in units of disintegrations per minute or microcuries. Leak test records should be kept until final disposition of the source is accomplished. A small sealed capsule may be tested by washing for a few minutes in a detergent solution. An aliquot 等分试样 of this solution should then be counted.

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An absorbent liner in the storage container normally in contact with the source will also reveal leakage if it is contaminated. Leak tests of devices from which the encapsulated source cannot be removed or is too large to handle should be made by wiping the accessible surface or aperture of the device nearest to the storage position of the source. Detection of contaminants on the housing or surface of a neutron source may not indicate source leakage but may be due to induced activity. Confirmation of leakage may require identification of the contaminant. In leak testing of radioactive sources, special equipment may be necessary for radiation exposure control. Depending on the activity of the source, shielding may be required to keep the leak tester’s exposure as low as possible. The actual leak test wipe should be done by using tongs or forceps and not the fingers. Rubber gloves should be used to minimize hand contamination. The wipes should be taken quickly and the source returned to its designated container.

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The actual leak test wipe should be done by using tongs or forceps and not the fingers. Rubber gloves should be used to minimize hand contamination. The wipes should be taken quickly and the source returned to its designated container.

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https://www.lanl.gov/newsroom/photo/index.php

Radiation Effects on Animals

http://galleryhip.com/radiation-effects-on-animals.html

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Radiation Effects on Animals

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Radiation Effects on Animals

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Radiation Leakages

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Radiation Leakages

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Radiation Leakages

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Radiation Leakages

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Radiation Leakages

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7.66 μSv

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Exercises Question: In how many hours the radiation worker will exceed the quarterly allowable exposure limit?

Answer: The annual allowable exposure is 5R ≡ 0.05 Sv ≡ 50,000μSv Quarterly limit is 50,000/4 = 12500μSv The recorded dose rate was 7.66 μSv/Hr. The radiation worker will exceed the quarterly limit within = 12,500/7.66 = 1,632hours of working in the mentioned area.

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PART 4. Basic Exposure Control

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Physical Safeguards and Procedural Controls As long as the radiation source remains external, exposure of the individual may be terminated by removing the individual from the radiation field, by removing the source or by switching off a radiation producing machine. If the external radiation field is localized, exposure to individuals may be limited readily by shielding or by denying access to the field of radiation.

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Physical Safeguards Physical safeguards include all physical equipment used to restrict access of persons to radiation sources or to reduce the level of exposure in occupied areas. These include shields, barriers, locks, alarm signals and source shutdown mechanisms. Planning and evaluation of physical safeguards should begin in the early phases of design and construction of an installation.

Detailed inspection and evaluation of the radiation safety of equipment are mandatory at the time of the installation’s initial use. Additional investigations are necessary periodically to ensure that the effectiveness of the safeguards has not decreased with time or as a result of equipment changes.

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Procedural Controls Procedural controls include all instructions to personnel regarding the performance of their work in a specific manner for the purpose of limiting radiation exposure. Training programs for personnel often are necessary to promote observance of such instructions. Typical instructions concern mode of use of radiation sources, limitations on proximity to sources, exposure time and occupancy of designated areas and the sequence or kinds of actions permitted during work with radiation sources. Periodic area surveys and personnel monitoring are necessary to ensure the adequacy of and compliance with established procedural controls.

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Classes of Installations for X-Rays and Gamma Rays There are four types of nonmedical X-ray and gamma ray installations: (1) protective, (2) enclosed, (3) unattended and (4) open. â– Protective Installation This class provides the highest degree of inherent safety because the protection does not depend on compliance with any operating limitations. The requirements include the following.

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1. Source and exposed objects are in a permanent enclosure within which no person is permitted during irradiation.

2. Safety interlocks are provided to prevent access to the enclosure during irradiation.

3. If the enclosure is of such a size or is so arranged that occupancy cannot be readily determined by the operator, the following requirements should also be provided: (a) fail safe audible or visible warning signals to indicate the source is about to be used; (b) emergency exits; (c) effective means within the enclosure of terminating the exposure (sometimes called scramming).

4. The radiation exposure 50 mm (2.0 in.) outside the surface of the enclosure cannot exceed 5 ÎźSv (0.5 mR) in any 1 h.

5. Warning signs of prescribed wording at prescribed locations.

6. No person may be exposed to more than the permissible doses. The low allowable exposure level necessitates greater inherent shielding. At high energies in the megavolt region with high workloads, the required additional shielding may be extremely expensive. For example, in the case of cobalt-60, the required concrete thickness will have to be about 0.3 m (1 ft) greater than for the enclosed type.

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â– Enclosed Installation This class usually offers the greatest advantages for fixed installations with low use and occupancy. With proper supervision this class offers a degree of protection similar to the protective installation. The requirements for an enclosed installation include items 1, 2, 3, 5 and 6, above, plus a different item 4.

4. The exposure at any accessible and occupied area 0.3 m (1 ft) from the outside surface of the enclosure does not exceed 100 ÎźSv (10 mR) in any 1 h.

The exposure at any accessible and normally unoccupied area 0.3 m (1 ft) from the outside surface of the enclosure does not exceed 1 mSv (100 mR) in any 1 h. This class of installation requires administrative procedures to avoid exceeding the permissible doses. The tradeoff between (1) the intrinsic but initially expensive safety of a protective installation and (2) the required continuing supervision and consequences of an overexposure in an enclosed installation should be carefully considered in the planning stages of a new facility.

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â– Unattended Installation This class consists of automatic equipment designed and manufactured by a supplier for a specific purpose that does not require personnel in attendance for operation. The requirements for this class include the following.

1. The source is installed in a single purpose device.

2. The source is enclosed in a shield, where the closed and open positions are identified and a visual warning signal indicates when the source is on.

3. The exposure at any accessible location 0.3 m (1 ft) from the outside surface of the device cannot exceed 20 ÎźSv (2 mR) in any 1 h.

4. The occupancy in the vicinity of the device is limited so that the exposure to any individual cannot exceed 5 mSv (0.5 R) in a year.

5. Warning signs are used.

6. Service doors to areas where exposure can exceed the measurements in items 3 and 4 above must be locked or secured with fasteners requiring special tools available only to qualified service personnel.

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â– Open Installation This class can only be used when operational requirements prevent other classes, such as in mobile and portable equipment where fixed shielding cannot be used. Mobile or portable equipment used routinely in one location should be made to meet the requirements of one of the fixed installation classes. Adherence to safe operating procedures is the main safeguard to overexposure. The requirements include the following.

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1. The perimeter of any area in which the exposure can exceed 1 mSv (100 mR) in any 1 h must be posted as a very high radiation area.

2. No unauthorized or unmonitored person may be permitted in the high radiation area during irradiation. In cases of unattended operation, positive means, such as a locked enclosure, shall be used to prevent access.

3. The perimeter of any area in which the radiation level exceeds 50 ÎźSv (5 mR) in any 1 h must be posted as a radiation area.

4. The equipment essential to the use of the source must be inaccessible to unauthorized use, tampering or removal. This shall be accomplished by the attendance of a knowledgeable person or other means such as a locked enclosure.

5. No person can be exposed to more than the permissible doses.

6. For reasons of safety and security, restricted areas must be clearly defined and marked. Means of surveillance to enforce the restrictions are needed.

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Output of Radiation Sources Table 3 lists some data on gamma ray sources of interest for industrial purposes. Table 4 lists some typical radiation machine outputs for varying voltages.

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TABLE 3. Gamma ray sources.

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TABLE 4. Forward X-ray intensity from optimum target.

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Isotope Dose Rate

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http://www.iem-inc.com/information/tools/gamma-ray-dose-constants

Isotope Dose Rate – Beta Emission

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http://www.radprocalculator.com/Beta.aspx

Working Time This is the allowable working time in hours per week for a given exposure rate.

For example, for an exposure rate of 100 μSv·h–1 (10 mR·h–1) to the whole body:

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Working Time This is the allowable working time in hours per week for a given exposure rate.

For example, for an exposure rate of 7.66 μSv·h–1 (10 mR·h–1) to the whole body:

7.66 130

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Working Distance The inverse square law applied to radiation states that the dose rate from a point source is inversely proportional to the square of the distance from the origin of the radiation source provided that (1) the dimensions of the radiation source are small compared with the distance and (2) no appreciable scattering or absorption of the radiation occurs in the media through which the radiation travels.

In practice, the first requirement is satisfied whenever the distance involved is at least ten times greater than the largest source dimension. In situations where there is insignificant scattering or absorption, the primary beam is the total radiation field.

For example, consider a 3.7 GBq (100 mCi) iridium-192 source in air in the shape of a pencil, 6.3 mm (0.25 in.) diameter and 0.13 m (5.0 in.) long. What would the working time be at 3.0 m? First, solve for 1 m. From Table 3, the gamma ray constant for iridium-192 is 135 μSv·GBq–1·h–1 at 1 m (0.5·Ci– 1·R·h–1 at 1 m). Therefore: Charlie Chong/ Fion Zhang

Exercise: For example, consider a Source type: Iridium 192 Activity: 3.7 GBq (100 mCi) Sizes: 6.3 mm (0.25 in.) diameter and 0.13 m (5.0 in.) long.

What would the working time per week be at 3.0 m? First, solve for 1 m. From Table 3, the gamma ray constant for iridium-192 is 135 μSv·GBq–1·h–1 at 1 m (0.5·Ci–1·R·h–1 at 1 m).

Therefore: Exposure rate = 0.135 x 3.7 = 0.4995 mSvh-1 Exposure rate at 3m = 0.4995/32 = 0.0555mSvh-1 Allowable dose per week = 1mSv Allowable time per week = 1/0.0555 = 18 hours.

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Exposure Rate

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Exposure Rate

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Because 3.0 m is obviously more than 10 times 0.13 m (5.0 in.), the inverse square law applies. Also, scattering is not a problem. Using the inverse square law gives the exposure rate at 3 m:

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Exposure Rate at 3m

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Equations 8 and 9 finally give the working time at 3 m:

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Occupational Personnel

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http://iisndt.com.bd/?services=radiographic-testing

Occupational Personnel

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http://iisndt.com.bd/?services=radiographic-testing

PART 5. Shielding

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Protective Enclosures Because of scattered radiation, protection for the operator and other personnel working in the neighborhood often requires shielding of the part being radiographed and any other material exposed to the direct beam, in addition to the shield for the source itself. Preferably the source and materials being examined should be enclosed in a room or hood with the necessary protection incorporated into the walls (Fig. 6).

Shields can be classified as either primary or secondary. Primary shields are designed to shield against the primary radiation beam; secondary shields are only thick enough to protect against tube housing leakage and scattered radiation. Therefore, the X-ray tube or source should not be pointed toward secondary shields. For this reason, mechanical stops should be used to restrict tube housing orientations toward primary barriers. Operating restrictions, such as not pointing the beam at certain walls or the ceiling, should be spelled out in the operating procedures.

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FIGURE 6. Rooms offering radiation shielding: (a) concrete shooting booth; (b) modular radiation enclosure. (a)

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FIGURE 6. Rooms offering radiation shielding: (a) concrete shooting booth; (b) modular radiation enclosure. (b)

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Protective materials are available in panels so that radiation barriers may be customized for work areas of various sizes. Mobile work rooms with modular designs are also available, offering the same flexibility in size and location (Fig. 6b). When changes in operating conditions are contemplated, the radiation safety officer (RSO) should be contacted for consultation and for surveys as needed to determine additional shielding requirements. For design purposes, the primary beam should not be pointed at a high personnel occupancy space and the distance from the radiation source to any occupied space should be as great as is practical. Scattered radiation usually has a lower effective energy than the primary beam and may, therefore, be easier to shield.

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Skyshine In the design of facilities, there is often a question concerning the magnitude of shielding required for the roof over the building. As an ordinary weather roof provides little if any attenuation for radiation directed up, there is a significant probability that radiation reflected back from the atmosphere will be unacceptable in the immediate area of the facility.

See Fig. 7 for X-rays and gamma rays this radiation: (1) increases roughly as 立, where 立 is the solid angle subtended by the source and shielding walls, (2) (2) decreases with (ds)2, where ds is the horizontal distance from the source to the observation point and (3) (3) decreases with (di)2, where di is the vertical distance from the source to about 2 m (6.5 ft) above the roof.

The shield thickness necessary to reduce the radiation to an acceptable level may be calculated according to published techniques and may alternatively be designed into the roof structure or mounted over the source with a lateral area sufficient to cover the solid angle 立. Similar statements apply to neutron skyshine, except that the functional dependences of the radiation at ds are slightly different for 立 and ds.

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FIGURE 7. Shielding above radiation source reduces radiation reflected from atmosphere. Such radiation is called skyshine.

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Skyshine.

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Skyshine.

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Skyshine.

This Figure shows tracks of photons from a skyshine calculation. The ceiling and front wall of the radiography room (blue) are transparent in the figures. The photons are emitted in an upwards conical direction from a point near the floor. A PTRAC filter in MCNP was used to select histories that crossed a surface to the right of the room. The tracks are colored by energy from 0 MeV (black) to 8 MeV (orange).

The energy legend is shown in next Figure Frames Link that shows several frames from the animation of the tracks. The particle positions are shown as points.

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http://www.whiterockscience.com/moritz/aex.html

Charlie Chong/ Fion Zhang

http://www.whiterockscience.com/moritz/aex.html

Skyshine- Animation

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The frames are labeled by the time in shakes (10-8 second). At 2 shakes, the spherical front of energetic photons is within the room. At 5 shakes, the front has passed through the ceiling where scatterings have decreased the average energy in the front and resulted in downward directed low energy photons. Several photons have penetrated the right wall. As the front continues to move upward (8 and 19 shakes), scatterings in the air result in downward moving photons. By 26 shakes, the front has moved out of the modeled space. Trailing track segments show the direction of the photons; changes in the track directions indicate scatterings.

In next Figure, a filter is used to exclude branches that terminate by escape.

The left panel shows the tracks with the exclusion filter applied. The other panels are frames from the animation with trailing track segments. Two segments at the top of the 15 shakes frame exhibit down scattering in both direction and energy. The 52 shakes frame shows a photon scattering off of the roof.

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This Figure is a frame from an animation with trailing tracks. The set of tracks visible was reduced by pruning the tracks to an air cell to the right of the room.

Pruning selects the branches in a history that lead to a specified cell or surface. The branches that do not contribute to the path and the histories that do not encounter the cell or surface are not shown

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Skyshine (Radiation) skyshine describes the ionizing radiation emitted by a nuclear technical or medical facility, reaching the facility's surroundings not directly, but indirectly through reflection and scattering at the atmosphere back to earth's surface. This effect can happen, when the shielding barrier around the source of radiation is open at the top. In a wider sense, skyshine also describes radiation reflected off the ceiling inside a nuclear facility.

The intensity of radiation measured at the surface immediately surrounding the facility increases with growing distance from the shielding barrier to reach a maximum and then fall again continuously with further increasing distance.

Depending on the type of radiation the maximum is reached at different distances from the source of radiation. For example, x-rays emitted from linear accelerators reached maxima of 18 MeV at a distance of 13.6 m and 6 MeV at 4.6 m in studies.

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https://en.wikipedia.org/wiki/Skyshine

Schematic of AVR reactor originally without top shielding Schematic of skyshine effect (S: soĂşrce of radiation, SH: shielding, D: detector, red arrows: paths of ionizing particles (neutrons, photons), blue line: skyshine intensity on surface with maximum M).

Between 1967 and 1975 significant radiation damage of the surroundings was caused by radiation skyshine at and near the AVR reactor in JĂźlich, Germany, which, in its original BBC construction, lacked a top shielding barrier.

In 2011, the skyshine effect reached media attention in the controversy around the radioactive waste repository Gorleben (de) after higher levels of radiation were measured outside the facility, despite it being shielded by a shielding wall

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https://en.wikipedia.org/wiki/Skyshine

Schematic of AVR reactor originally without top shielding.

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https://en.wikipedia.org/wiki/Skyshine

Materials Common materials such as concrete and lead can be used as absorbers or shields to reduce personnel exposures. Beta or electron radiation is completely stopped by the thicknesses of material shown in Fig. 8.

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FIGURE 8. Maximum range of beta particles as function of energy in various materials indicated.30

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HVL & TVL The thickness of any material that will halve the amount of radiation passing through the material is referred to as the half value layer (HVL). Similarly, the thickness that will reduce the radiation to one tenth is referred to as the tenth value layer (TVL). (See Tables 5 and 6 and see Figs. 9 and 10) These terms imply an exponential function for transmitted radiation in terms of shield thickness.

Figures 9 and 10, however, show that the transmission curves are not completely linear on a semilogarithmic plot.Hence, the listed half value layers and tenth value layers in Tables 5 and 6 are approximate, obtained with large attenuation.

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FIGURE 9. Transmission through lead of gamma rays from selected radionuclides.

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FIGURE 10. Transmission through concrete (density of 2.35 g·cm–3 [147 lbm·ft –3]) of gamma rays from radium, cobalt–60, gold-198 and iridium-192.3

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Table 5. Shielding equivalents: approximate tenth (TVL) and half value (HVL) layer thicknesses in lead and concrete for several gamma ray sources.3,27

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EXAM Alert!

Source Ra226 Co60 Cs137 Ir192 Au198

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TVLPb 56mm 41mm 21mm 20mm 11mm

HVLPb 16mm 12mm 06mm 06mm 03mm

TABLE 6. Shielding equivalents: approximate half value layers (HVL) and tenth value layers (TVL) for lead and concrete for various X-ray tube potentials.

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TABLE 7. Densities of commercial building materials.3,27

a. One part portland cement and two parts sand. b. Barite with calcium aluminate and colemanite. c. One part cement, two parts sand and four parts gravel.

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Table 7 lists densities of commercial building materials. For X-radiation and gamma radiation, the absorption process depends largely on compton absorption and scattering, which in turn increase with the atomic electron density.

As a first approximation, electron density varies directly with the mass density of a material. Hence, the denser building materials are usually better shielding materials for a given thickness of material. On a mass basis, shielding materials are much the same above about 500 keV. Where space is a problem, lead is often used to achieve the desired shield attenuation. Lead, however, requires extra structural support because it is not self-supporting.

Concrete is by far the most commonly used shielding material for economic, structural and local availability reasons — in addition to desirable shielding characteristics. Where space considerations are important depleted uranium shields are expensive but offer excellent solutions to difficult problems. Table 5 lists half value layers and tenth value layers for several commonly used gamma ray emitting radionuclides. Table 6 lists similar information for X-ray peak voltages. Figures 9 and 10 show actual transmission through lead and concrete for the gamma ray emitting radionuclides.

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Figure 11 shows a representative transmission through concrete. Similar charts are available for steel, lead and other materials for X- ay beams of various peak energies.1,28 These charts present broad beam shielding information, which includes all scattered radiation resulting from deflection of the primary gamma or X-rays within the shield as well as absorption of the primary radiation. Most engineering applications need to consider broad beam geometry. Narrow beam geometry, where only the primary beam needs consideration, is seldom encountered in practice.

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FIGURE 11. Transmission through concrete (density of 2.35 g·cm–3 [147 lbm·ft–3]) of X-rays produced by 0.1 to 0.4 MeV electrons under broad beam conditions. Four curves shown represent transmission in dose equivalent index ratio. First three electron energies were accelerated by voltages with pulsed wave form. Fourth electron energy (0.4 MeV) was accelerated by constant potential generator. Top scale indicates required mass thickness, or mass per unit area, g·cm–2 (lbm·in.–2). Concrete of different density may be used if required mass thickness is achieved. Where weight is considered, this scale can be used in selection of optimum shielding material.

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Legend A. 0.10 MeV. B. 0.15 MeV. C. 0.25 MeV. D. 0.40 MeV.

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PART 6. Neutron Radiographic Safety

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Introduction Neutrons are of interest in radiography because their interaction with matter is significantly different from X-rays or gamma rays. Neutrons are absorbed and scattered more in low atomic numbered (low Z) materials than high Z materials. Thus, plastics, explosives and some organic materials can be examined for discontinuities with little interference from encapsulating metals and electronic parts and wiring.

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Neutron Attenuation

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http://mnrc.ucdavis.edu/neutronimaging.html

Neutron Attenuation

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Neutron Sources Radioactive Neutron Sources Radiation measurement techniques specific to neutron radiation are discussed elsewhere. â– Spontaneous Fission Neutron Sources These sources are attractive because of their fissionlike spectrum, relatively low gamma ray yield and their small mass. Californium-252 has been used for stationary and mobile systems.

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Californium-252 Capsules

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Californium-252 Capsules

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Californium-252 Capsules

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Californium is a radioactive metallic chemical element with the symbol Cf and atomic number 98. The element was first made at the University of California, Berkeley in 1950 by bombarding curium with alpha particles ( helium-4 ions).

It is an actinide element, the sixth transuranium element to be synthesized, and has the second-highest atomic mass of all the elements that have been produced in amounts large enough to see with the unaided eye (after einsteinium). The element was named after California and the University of California. It is the heaviest element to occur naturally on Earth; heavier elements can only be produced by synthesis.

Two crystalline forms exist for californium under normal pressure: one above 900 °C and one below 900 °C. A third form exists at high pressure.

Californium slowly tarnishes in air at room temperature. Compounds of californium are dominated by a chemical form of the element, designated californium(III), that can participate in three chemical bonds.

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The most stable of californium's twenty known isotopes is californium-251, which has a half-life of 898 years. This short half-life means the element is not found in significant quantities in the Earth's crust. Californium-252, with a halflife of about 2.64 years, is the most common isotope used and is produced at the Oak Ridge National Laboratory in the United States and the Research Institute of Atomic Reactors in Russia.

Californium is one of the few transuranium elements that have practical applications. Most of these applications exploit the property of certain isotopes of californium to emit neutrons. For example, californium can be used to help start up nuclear reactors, and it is employed as a source of neutrons when studying materials with neutron diffraction and neutron spectroscopy. Californium can also be used in nuclear synthesis of higher mass elements; ununoctium (element 118) was synthesized by bombarding californium-249 atoms with calcium-48 ions. Use of californium must take into account radiological concerns and the element's ability to disrupt the formation of red blood cells by bioaccumulating in skeletal tissue.

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Physical properties

Californium is a silvery white actinide metal with a melting point of 900 ± 30 °C and an estimated boiling point of 1745 °C. The pure metal is malleable and is easily cut with a razor blade. Californium metal starts to vaporize above 300 °C when exposed to a vacuum. Below 51 K (−220 °C) californium metal is either ferromagnetic or ferrimagnetic (it acts like a magnet), between 48 and 66 K it is antiferromagnetic (an intermediate state), and above 160 K (−110 °C) it is paramagnetic (external magnetic fields can make it magnetic).

It forms alloys with lanthanide metals but little is known about them.

The element has two crystalline forms under 1 standard atmosphere of pressure: A double- hexagonal close-packed form dubbed alpha (α) and a face-centered cubic form designated beta (β). The α form exists below 900 °C with a density of 15.10 g/cm3 and the β form exists above 900 °C with a density of 8.74 g/cm3. At 48 GPa of pressure the β form changes into an orthorhombic crystal system due to de-localization of the atom's 5f electrons, which frees them to bond.

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The bulk modulus of a material is a measure of its resistance to uniform pressure. Californium's bulk modulus is 50 Âą 5 GPa, which is similar to trivalent lanthanide metals but smaller than more familiar metals, such as aluminium (70 GPa).

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History Californium was first synthesized at the University of California, Berkeley by the physics researchers Stanley G. Thompson, Kenneth Street, Jr., Albert Ghiorso, and Glenn T. Seaborg on or about February 9, 1950. It was the sixth transuranium element to be discovered; the team announced its discovery on March 17, 1950.

To produce californium, a microgram-sized target of curium-242 (24296Cm) was bombarded with 35 MeV- alpha particles (42He) in the 60-inch-diameter (1,500 mm) cyclotron at Berkeley, California, which produced californium-245 (24598Cf) plus one free neutron (n).

242

96Cm

+ 42He → 24598Cf + 10n

Only about 5,000 atoms of californium were produced in this experiment, and these atoms had a half-life of 44 minutes.

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The discoverers named the new element after California and the University of California. This was a break from the convention used for elements 95 to 97, which drew inspiration from how the elements directly above them in the periodic table were named. However, the element directly above element 98 in the periodic table, dysprosium, has a name that simply means "hard to get at" so the researchers decided to set aside the informal naming convention.

They added that "the best we can do is to point out [that] ... searchers a century ago found it difficult to get to California."

Weighable quantities of californium were first produced by the irradiation of plutonium targets at the Materials Testing Reactor at the Idaho National Laboratory; and these findings were reported in 1954. The high spontaneous fission rate of californium-252 was observed in these samples. The first experiment with californium in concentrated form occurred in 1958. The isotopes californium-249 to californium-252 were isolated that same year from a sample of plutonium-239 that had been irradiated with neutrons in a nuclear reactor for five years. Two years later, in 1960, Burris Cunningham and James Wallman of the Lawrence Radiation Laboratory of the University of California created the first californium compounds—californium trichloride, californium oxychloride, and californium oxide—by treating californium with steam and hydrochloric acid.

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The High Flux Isotope Reactor (HFIR) at the Oak Ridge National Laboratory (ORNL) in Oak Ridge, Tennessee, started producing small batches of californium in the 1960s. By 1995, the HFIR nominally produced 500 milligrams of californium annually. Plutonium supplied by the United Kingdom to the United States under the 1958 US-UK Mutual Defence Agreement was used for californium production.

The Atomic Energy Commission sold californium-252 to industrial and academic customers in the early 1970s for $10 per microgram and an average of 150 mg of californium-252 were shipped each year from 1970 to 1990. Californium metal was first prepared in 1974 by Haire and Baybarz who reduced californium(III) oxide with lanthanum metal to obtain microgram amounts of sub-micrometer thick films.

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The 60-inch-diameter (1,500 mm) cyclotron used to first synthesize californium

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Production Californium is produced in nuclear reactors and particle accelerators.

Californium-250 is made by bombarding berkelium-249 (24997Bk) with neutrons, forming berkelium-250 (25097Bk) via neutron capture (n,γ) which, in turn, quickly beta decays (β−) to californium-250 (25098Cf) in the following reaction: 249

250 Bk 97Bk(n,γ) 97

→ 25098Cf + β−

Bombardment of californium-250 with neutrons produces californium-251 and californium-252. (n,γ) 25198Cf 251 Cf (n,γ) 252 Cf 98 98 250

98Cf

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Prolonged irradiation of americium, curium, and plutonium with neutrons produces milligram amounts of californium-252 and microgram amounts of californium-249. As of 2006, curium isotopes 244 to 248 are irradiated by neutrons in special reactors to produce primarily californium-252 with lesser amounts of isotopes 249 to 255.

Microgram quantities of californium-252 are available for commercial use through the U.S. Nuclear Regulatory Commission. Only two sites produce californium-252 – the Oak Ridge National Laboratory in the United States, and the Research Institute of Atomic Reactors in Dimitrovgrad, Russia. As of 2003, the two sites produce 0.25 grams and 0.025 grams of californium-252 per year, respectively.

Three californium isotopes with significant half-lives are produced, requiring a total of 15 neutron captures by uranium-238 without nuclear fission or alpha decay occurring during the process. Californium-253 is at the end of a production chain that starts with uranium-238, includes several isotopes of plutonium, americium, curium, berkelium, and the californium isotopes 249 to 253 (see diagram).

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Transuranium Isotopes - Scheme of the production of californium-252 from uranium-238 by neutron irradiation

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Application Californium-252 has a number of specialized applications as a strong neutron emitter, and each microgram of fresh californium produces 139 million neutrons per minute (1.39 x 109 n/min) . This property makes californium useful as a neutron startup source for some nuclear reactors and as a portable (non-reactor based) neutron source for neutron activation analysis to detect trace amounts of elements in samples. Neutrons from californium are employed as a treatment of certain cervical and brain cancers where other radiation therapy is ineffective. It has been used in educational applications since 1969 when the Georgia Institute of Technology received a loan of 119 Âľg of californium-252 from the Savannah River Plant. It is also used with online elemental coal analyzers and bulk material analyzers in the coal and cement industries.

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Neutron penetration into materials makes californium useful in detection instruments such as fuel rod scanners; neutron radiography of aircraft and weapons components to detect corrosion, bad welds, cracks and trapped moisture; and in portable metal detectors. Neutron moisture gauges use californium-252 to find water and petroleum layers in oil wells, as a portable neutron source for gold and silver prospecting for on-the-spot analysis, and to detect ground water movement.

The major uses of californium-252 in 1982 were, in order of use, reactor startup (48.3%), fuel rod scanning (25.3%), and activation analysis (19.4%). By 1994 most californium-252 was used in neutron radiography (77.4%), with fuel rod scanning (12.1%) and reactor start-up (6.9%) as important but distant secondary uses.

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Californium-251 has a very small critical mass (about 5 kg), high lethality, and a relatively short period of toxic environmental irradiation. The low critical mass of californium led to some exaggerated claims about possible uses for the element.

In October 2006, researchers announced that three atoms of ununoctium (element 118) had been identified at the Joint Institute for Nuclear Research in Dubna, Russia, as the product of bombardment of californium-249 with calcium-48, making it the heaviest element ever synthesized. The target for this experiment contained about 10 mg of californium-249 deposited on a titanium foil of 32 cm2 area. Californium has also been used to produce other transuranium elements; for example, element 103 (later named lawrencium) was first synthesized in 1961 by bombarding californium with boron nuclei.

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Decay of CF-252 → 24896Cm + 42He2+ 252 CF → SF + 1 n(s) 0 98

252

98CF

Californium-252 Applications • • • • • •

Oil Well Logging (OWL) – Cf-252 is used in oil exploration applications such as wireline logging and logging while drilling.

Thickness Gauging – Californium-252 is used to measure light alloys, glass, plastics, and rubber for which beta sources are not suitable.

Reactor Startup – Californium reactor start-up sources are enclosed in welded, corrosion-resistant encapsulations, designed to yield high levels of neutron output without compromising the integrity of the source.

Fuel Rod Scanning – Californium measures the content of fissile material in mixed oxide fuel rods.

Materials Analysis – Californium-252 excites radiation in non-destructive testing elemental analysis applications.

Medical – Cf-252 is widely used for a variety of medical research and healthcare applications, including cancer treatment.

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http://www.qsa-global.com/californium-252/

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http://periodictable.com/Isotopes/098.252/index.full.html

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Precautions Californium that bioaccumulates in skeletal tissue releases radiation that disrupts the body's ability to form red blood cells. The element plays no natural biological role in any organism due to its intense radioactivity and low concentration in the environment.

Californium can enter the body from ingesting contaminated food or drinks or by breathing air with suspended particles of the element. Once in the body, only 0.05% of the californium will reach the bloodstream. About 65% of that californium will be deposited in the skeleton, 25% in the liver, and the rest in other organs, or excreted, mainly in urine. Half of the californium deposited in the skeleton and liver are gone in 50 and 20 years, respectively. Californium in the skeleton adheres to bone surfaces before slowly migrating throughout the bone.

The element is most dangerous if taken into the body. In addition, californium249 and californium-251 can cause tissue damage externally, through gamma ray emission. Ionizing radiation emitted by californium on bone and in the liver can cause cancer.

Charlie Chong/ Fion Zhang

â– Accelerator Sources Constant voltage accelerators such as van de graaff and cockcroft-walton accelerators can produce energies up to about 20 MeV for protons and deuterons and still higher energies for alpha particles and heavy ions. Small accelerators using deuterons of 100 to 200 keV energy can produce large numbers of 14 MeV neutrons when using a tritiated (Tritium) target. High frequency positive ion accelerators include the cyclotron, synchrocyclotron, proton synchrotron and heavy ion linear accelerator. These are capable of producing a wide range of neutron energies.

Protons above 10 MeV will produce neutrons when striking almost any material. High frequency electron accelerators such as the betatron produce X-rays through the interaction of the accelerated electrons with the target.

The X-rays in turn produce photoneutrons (Îł,n) , most with energies of a few MeV but with some neutrons having energies up to near the maximum energy of the accelerator.

Charlie Chong/ Fion Zhang

â– Nuclear Reactor Sources Neutron production in reactors occurs as a result of the fission process. In the usual operating mode the number of fissions (and neutrons) is essentially constant in time. The neutron energies range from thermal to 15 MeV with the number over 10 MeV being small.

Charlie Chong/ Fion Zhang

Shielding â– Fast Neutrons Adequate shielding against neutrons will often attenuate gamma radiation to acceptable levels at both reactors and accelerators. Water and other hydrogenous shields may constitute an important exception to this rule.

Ordinary or heavy aggregate concrete or earth are the recommended materials in most installations. Any economy achieved by water filled tanks is likely to be offset by maintenance difficulties. Both paraffin and oil, although good neutron absorbers, are fire hazards and should not be used in large stationary shields. Techniques of shielding calculations are discussed in detail elsewhere. The importance of concrete as a structural and shielding material merits special mention. Its use for gamma and X-ray shielding has been previously discussed. Because of its relatively high hydrogen and oxygen content, it is also a good neutron shield. The subject of shielding calculations for neutrons is complex and should be performed by specialists.

Benchmarks include approximate tenth value layers (TVL) of 250 mm (10 in.) of concrete for 14 MeV neutrons and 150 mm (6 in.) for 0.7 MeV neutrons.

Charlie Chong/ Fion Zhang

â– Thermal Neutrons Generally the energies associated with thermal neutrons are less than 1 eV (0.3MeV) . For radiation protection the most important interaction of thermal neutrons with matter is radioactive capture. In this process, the neutron is captured by the nucleus with the emission of gamma radiation. A shield adequate for fast neutrons usually will be satisfactory for thermal neutrons.

The low quality factor (QF = 2) for thermal neutrons (0.025 eV) makes their biological consequence considerably less than for fast neutrons

Charlie Chong/ Fion Zhang

Radiation Safety Quizzes

Charlie Chong/ Fion Zhang

https://www.nde-ed.org/EducationResources/CommunityCollege/RadiationSafety/Quizzes/rtsafetyquizzes.htm

Charlie Chong/ Fion Zhang

Q1 Which of the following have a negative charge?

Alpha particles Beta particles Gamma particles Only A and B Q2 Radiation is a form of: Atomic waveform Energy Decayed plutonium Active isotopes

Charlie Chong/ Fion Zhang

https://www.nde-ed.org/EducationResources/CommunityCollege/RadiationSafety/Quizzes/rtsafetyquizzes.htm

Q3 Depending upon the ratio of neutrons to protons within its nucleus: An isotope is always unstable An isotope is always stable An isotope can be stable or unstable The x-ray source can emit a wide variety of energy levels Q4 ALARA stands for: As Low As Responsibly Acceptable Alarm Loss Activated Radiation Activated As Low As Reasonable Achievable As Low As Reasonably Attenuated Q5 Electromagnetic radiation acts like a stream of small “packets� of energy called: Protons Alpha kickers Photons Beta spikes

Charlie Chong/ Fion Zhang

Q6 All people have radioactive isotopes inside their bodies.

True False Q7 Radium could be used to radiograph casting as thick as: 2 inches 4 inches 6 inches 12 inches Q8 Radioisotopes such as Iridium 192 and Cobalt 60 are used in an industrial setting and are carried in a container called a: Camera Vault Safe Overpack

Charlie Chong/ Fion Zhang

Q9 When radiation interacts with a cell wall or DNA: The cell becomes energized The radiation shifts to a different waveform The cell becomes radioactive The cell either dies or becomes a different kind of cell such as a cancer cell Q10 Which of the following is used to provide a permanent record of radiation exposure?

Alarm ratemeter Survey meter Dosimeter Film badge Q11 Which of the following has the most material penetrating power?

Iridium 192 Cobalt 60 Cobalt 59 Iridium 191

Charlie Chong/ Fion Zhang

Q12 The half-life of Iridium 192 is approximately: 74 days 74 years 5 days 5 years Q13 Which of the following is a rate measuring instrument?

Film badge Survey meter TLD All of the above Q14 Which of the following is an example of electromagnetic radiation?

Radio waves Light waves Gamma rays All of the above

Charlie Chong/ Fion Zhang

Q15 How much radiation is a radiographer allowed to receive in a calendar year?

15 rem 10 rem 50 rem 5 rem Q16 In general, the denser the material: The more radiation is reflected The better shielding it will provide The lower the atomic number The faster the exposure time Q17 The primary risk from occupational radiation exposure is the increased risk of: Cancer Blindness Abrasions None of the above

Charlie Chong/ Fion Zhang

Q18 Which of the following has the shortest wavelength?

Radio waves Light waves Gamma rays Alpha rays Q19 The principle advantage of a pocket dosimeter is its ability to: Produce an accurate reading over a long period of time Never needing to be calibrated Provide some protection of radiation Provide the wearer an immediate reading of radiation exposure Q20 What percentage of human exposure comes from outer space, rocks, soil. radon gas and the human body?

20% 40% 60% 80%

Charlie Chong/ Fion Zhang

â– Accelerator Sources Constant voltage accelerators such as van de graaff and cockcroft-walton accelerators can produce energies up to about 20 MeV for protons and deuterons and still higher energies for alpha particles and heavy ions. Small accelerators using deuterons of 100 to 200 keV energy can produce large numbers of 14 MeV neutrons when using a tritiated (Tritium) target. High frequency positive ion accelerators include the cyclotron, synchrocyclotron, proton synchrotron and heavy ion linear accelerator. These are capable of producing a wide range of neutron energies.

Protons above 10 MeV will produce neutrons when striking almost any material. High frequency electron accelerators such as the betatron produce X-rays through the interaction of the accelerated electrons with the target.

The X-rays in turn produce photoneutrons (Îł,n) , most with energies of a few MeV but with some neutrons having energies up to near the maximum energy of the accelerator.

Charlie Chong/ Fion Zhang

â– Nuclear Reactor Sources Neutron production in reactors occurs as a result of the fission process. In the usual operating mode the number of fissions (and neutrons) is essentially constant in time. The neutron energies range from thermal to 15 MeV with the number over 10 MeV being small.

Charlie Chong/ Fion Zhang

Shielding â– Fast Neutrons Adequate shielding against neutrons will often attenuate gamma radiation to acceptable levels at both reactors and accelerators. Water and other hydrogenous shields may constitute an important exception to this rule.

Ordinary or heavy aggregate concrete or earth are the recommended materials in most installations. Any economy achieved by water filled tanks is likely to be offset by maintenance difficulties. Both paraffin and oil, although good neutron absorbers, are fire hazards and should not be used in large stationary shields. Techniques of shielding calculations are discussed in detail elsewhere. The importance of concrete as a structural and shielding material merits special mention. Its use for gamma and X-ray shielding has been previously discussed. Because of its relatively high hydrogen and oxygen content, it is also a good neutron shield. The subject of shielding calculations for neutrons is complex and should be performed by specialists.

Benchmarks include approximate tenth value layers (TVL) of 250 mm (10 in.) of concrete for 14 MeV neutrons and 150 mm (6 in.) for 0.7 MeV neutrons.

Charlie Chong/ Fion Zhang

â– Thermal Neutrons Generally the energies associated with thermal neutrons are less than 1 eV (0.3MeV) . For radiation protection the most important interaction of thermal neutrons with matter is radioactive capture. In this process, the neutron is captured by the nucleus with the emission of gamma radiation. A shield adequate for fast neutrons usually will be satisfactory for thermal neutrons.

The low quality factor (QF = 2) for thermal neutrons (0.025 eV) makes their biological consequence considerably less than for fast neutrons

Charlie Chong/ Fion Zhang

Radiation Safety Quizzes

Charlie Chong/ Fion Zhang

https://www.nde-ed.org/EducationResources/CommunityCollege/RadiationSafety/Quizzes/rtsafetyquizzes.htm

Charlie Chong/ Fion Zhang

Q1 Which of the following have a negative charge?

Alpha particles Beta particles Gamma particles Only A and B Q2 Radiation is a form of: Atomic waveform Energy Decayed plutonium Active isotopes

Charlie Chong/ Fion Zhang

https://www.nde-ed.org/EducationResources/CommunityCollege/RadiationSafety/Quizzes/rtsafetyquizzes.htm

Q3 Depending upon the ratio of neutrons to protons within its nucleus: An isotope is always unstable An isotope is always stable An isotope can be stable or unstable The x-ray source can emit a wide variety of energy levels Q4 ALARA stands for: As Low As Responsibly Acceptable Alarm Loss Activated Radiation Activated As Low As Reasonable Achievable As Low As Reasonably Attenuated Q5 Electromagnetic radiation acts like a stream of small “packets� of energy called: Protons Alpha kickers Photons Beta spikes

Charlie Chong/ Fion Zhang

Q6 All people have radioactive isotopes inside their bodies.

True False Q7 Radium could be used to radiograph casting as thick as: 2 inches 4 inches 6 inches 12 inches Q8 Radioisotopes such as Iridium 192 and Cobalt 60 are used in an industrial setting and are carried in a container called a: Camera Vault Safe Overpack

Charlie Chong/ Fion Zhang

Q9 When radiation interacts with a cell wall or DNA: The cell becomes energized The radiation shifts to a different waveform The cell becomes radioactive The cell either dies or becomes a different kind of cell such as a cancer cell Q10 Which of the following is used to provide a permanent record of radiation exposure?

Alarm ratemeter Survey meter Dosimeter Film badge Q11 Which of the following has the most material penetrating power?

Iridium 192 Cobalt 60 Cobalt 59 Iridium 191

Charlie Chong/ Fion Zhang

Q12 The half-life of Iridium 192 is approximately: 74 days 74 years 5 days 5 years Q13 Which of the following is a rate measuring instrument?

Film badge Survey meter TLD All of the above Q14 Which of the following is an example of electromagnetic radiation?

Radio waves Light waves Gamma rays All of the above

Charlie Chong/ Fion Zhang

Q15 How much radiation is a radiographer allowed to receive in a calendar year?

15 rem 10 rem 50 rem 5 rem Q16 In general, the denser the material: The more radiation is reflected The better shielding it will provide The lower the atomic number The faster the exposure time Q17 The primary risk from occupational radiation exposure is the increased risk of: Cancer Blindness Abrasions None of the above

Charlie Chong/ Fion Zhang

Q18 Which of the following has the shortest wavelength?

Radio waves Light waves Gamma rays Alpha rays Q19 The principle advantage of a pocket dosimeter is its ability to: Produce an accurate reading over a long period of time Never needing to be calibrated Provide some protection of radiation Provide the wearer an immediate reading of radiation exposure Q20 What percentage of human exposure comes from outer space, rocks, soil. radon gas and the human body?

20% 40% 60% 80%

Charlie Chong/ Fion Zhang

Q1 Prolonged exposure to heat can effect a: Alarm ratemeter Survey meter Geiger counter Film badge Q2 Which of the following is a rate measuring instrument?

Survey meter Audible alarm Area monitor All of the above Q3 The ionization chamber survey meter usually measures radiation levels in the range of: Milliroentgens per hour Roentgens per hour Milliroentgens per minute Roentgens per minute

Charlie Chong/ Fion Zhang

Q4 The device that measures the total amount of exposure received during a measuring period is called a: Survey meter Geiger counter Dose measuring instrument All of the above Q5 Radiation is a form of: Atomic waveform Energy Decayed plutonium Active isotopes Q6 Some of the most common effects of ionizing radiation are: Inhibition of cell division Alteration of membrane permeability Chromosome aberrations All of the above

Charlie Chong/ Fion Zhang

Q7 The dislodging of one or more electrons from an atom is called: Ionization Refractology Half-life Isotope Q8 A dosimeter which is off scale would be considered: Fully charged Fully discharged Broken Transparent Q9 The half value layer for Cobalt 60 is the same as the half value layer for Iridium 192.

True False

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Q10 The term used to describe an interaction where electrons acquire energy from a passing charged particle but are not removed completely from their atom is called: Excitation Radiation An isotope Diffraction Q11 X-rays were discovered in 1895 by: Robert Conrad Marie Curie Pierre Curie Wilhelm Roentgen Q12 When radiation interacts with a cell wall or DNA: The cell becomes energized The radiation shifts to a different waveform The cell becomes radioactive The cell either dies or becomes a different kind of cell such as a cancer cell Charlie Chong/ Fion Zhang

Q13 Depending upon the ratio of neutrons to protons within its nucleus: An isotope is always unstable An isotope is always stable An isotope can be stable or unstable The x-ray source can emit a wide variety of energy levels Q14 How long after the Roentgen’s discovery, were radiation burns detected?

1 day 1 year 1 month 6 months Q15 All people have radioactive isotopes inside their bodies.

True False

Charlie Chong/ Fion Zhang

Q16 The time required for one half of the amount of unstable material to degrade into a more stable material is called: Half-time Half-life Half value layer Half-sign Q17 Which of the following is used to provide a permanent record of radiation exposure?

Alarm ratemeter Survey meter Dosimeter Film badge Q18 When the distance from the source of radiation is doubled, the amount of radiation received will be: Doubled Tripled Reduced by 1/2 Reduced by 1/4 Charlie Chong/ Fion Zhang

Q19 Which of the following have a positive charge?

Alpha particles Beta particles Gamma particles Only A and B Q20 The Curies discovered a radioactive element which they called: Uranium Cobalt Pitchblende Radium Q21 The half-life of Iridium 192 is approximately: 74 days 74 years 5 days 5 years

Charlie Chong/ Fion Zhang

Q22 The primary risk from occupational radiation exposure is the increased risk of: Cancer Blindness Abrasions None of the above Q23 What are the two types of radiation?

Particulate and electromagnetic Alpha and Beta Alpha and Gamma Positive and negative Q24 X-rays are produced: From a decaying isotope By a nuclear generator By high speed protons By an X-ray generator

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Q25 Gamma rays are produced by: Radioactive atoms Bremstrahlung K shell disintegration Television sets Q26 The cathode and anode are parts of: An iridium camera A cobalt camera X-ray system All of the above Q27 Which of the following have both energy and mass?

Alpha particles Beta particles Gamma particles Only A and B

Charlie Chong/ Fion Zhang

Q28 Which of the following is a personal monitoring device?

Alarm ratemeter Survey meter Geiger counter Film badge Q29 Cobalt 60 is produced by: Exposing Cobalt 59 to high energy x-rays Changing the number of protons in the nucleus Converting an element to a compound Adding an extra neutron Q30 Which of the following is packaged in a light proof, vapor proof envelope?

Alarm ratemeter Survey meter Geiger counter Film badge

Charlie Chong/ Fion Zhang

Q31 What does RSO stand for?

Radiation Service Officer Roentgen Safety Office Radiation Safety Officer Radiation Safety Organization Q32 If a technician has been working with an isotope and the dosimeter reads “off scale�: All work should be stopped immediately and the film badge should be turned in It should be re-zeroed and work should resume The assistant should take the rest of the radiographs There is a high chance that the radiographer will get cancer Q33 The strength of a source is called: Sequence radiation Refraction Activity Curies

Charlie Chong/ Fion Zhang

Q34 Which of the following are the two most common industrial gammaray sources?

Ir 192 and Beryllium 54 Radium and Beryllium Cobalt and Iridium X-ray and Lead Q35 Electromagnetic radiation acts like a stream of small “packets� of energy called: Protons Alpha kickers Photons Beta spikes

Charlie Chong/ Fion Zhang

Q1 The most significant source of man-made radiation exposure to the average person is from: Gamma rays Beta rays Medical procedures Alpha rays Q2 Some of the most common effects of ionizing radiation are: Inhibition of cell division Alteration of membrane permeability Chromosome aberrations All of the above Q3 TLD stands for: Thermoluminescent Dosimeter Thermal Latent Distance Time Life Dosimeter Translucent Latent Dosimeter

Charlie Chong/ Fion Zhang

Q4 Which of the following have both energy and mass?

Alpha particles Beta particles Gamma particles Only A and B Q5 Which of the following have a positive charge?

Alpha particles Beta particles Gamma particles Only A and B Q6 What does a collimator do?

It reduces the exposure time by ionizing the radiation before it hits the film It holds the film in place during an exposure It provides shielding from radiation There is no such thing as a collimator

Charlie Chong/ Fion Zhang

Q7 The target of an x-ray tube is often made from: Balsa wood Cobalt Tungsten Aluminum Q8 If a person received a radiation dose of 10 rem to the entire body (above background), his or her risk of dying from cancer would increase by one percent to a high of: 5% 10% 15% 21% Q9 The cathode and anode are parts of: An iridium camera A cobalt camera X-ray system All of the above

Charlie Chong/ Fion Zhang

Q10 Radioisotopes such as Iridium 192 and Cobalt 60 are used in an industrial setting and are carried in a container called a: Camera Vault Safe Overpack Q11 If a technician has been working with an isotope and the dosimeter reads “off scale�: All work should be stopped immediately and the film badge should be turned in It should be re-zeroed and work should resume The assistant should take the rest of the radiographs There is a high chance that the radiographer will get cancer Q12 Which of the following is a source of nonionizing radiation?

Ultraviolet light Infrared light Microwaves All of the above are nonionizing radiation Charlie Chong/ Fion Zhang

Q13 The half-life of Iridium 192 is approximately: 74 days 74 years 5 days 5 years Q14 The device that measures the total amount of exposure received during a measuring period is called a: Survey meter Geiger counter Dose measuring instrument All of the above Q15 When radiation interacts with a cell wall or DNA: The cell becomes energized The radiation shifts to a different waveform The cell becomes radioactive The cell either dies or becomes a different kind of cell such as a cancer cell

Charlie Chong/ Fion Zhang

Q16 What does RSO stand for?

Radiation Service Officer Roentgen Safety Office Radiation Safety Officer Radiation Safety Organization Q17 The half-life of Cobalt 60 is approximately: 74 days 74 years 5 days 5 years Q18 The strength of a source is called: Sequence radiation Refraction Activity Curies

Charlie Chong/ Fion Zhang

Q19 Which of the following has the shortest wavelength?

Radio waves Light waves Gamma rays Alpha rays Q20 One source of natural radiation is: Iridium 192 Cobalt 60 Cosmic radiation Nuclear power plants Q21 How long after the Roentgen’s discovery, were radiation burns detected?

1 day 1 year 1 month 6 months

Charlie Chong/ Fion Zhang

Q22 Radium could be used to radiograph casting as thick as: 2 inches 4 inches 6 inches 12 inches Q23 A state that has agreed to assume regulatory control of radioactive material within their borders is called: An agreement state An NRC state A proliferation state All of the above

Charlie Chong/ Fion Zhang

Q 24 X-rays are produced: From a decaying isotope By a nuclear generator By high speed protons By an X-ray generator Q25 Gamma rays are produced by: Radioactive atoms Bremstrahlung K shell disintegration Television sets

Charlie Chong/ Fion Zhang

Q26 Who discovered natural radioactivity?

Wilhelm Roentgen Marie Curie Henri Becquerel None of the above Q27 The instrument used to measure external radiation exposure for the day from gamma and x-rays worn by the radiographer is called a: Alarm ratemeter Pocket dosimeter Geiger counter Survey meter Q28 Depending upon the ratio of neutrons to protons within its nucleus: An isotope is always unstable An isotope is always stable An isotope can be stable or unstable The x-ray source can emit a wide variety of energy levels

Charlie Chong/ Fion Zhang

Q29 Which of the following is a rate measuring instrument?

Survey meter Audible alarm Area monitor All of the above Q30 Which of the following is a rate measuring instrument?

Film badge Survey meter TLD All of the above Q31 The ionization chamber survey meter usually measures radiation levels in the range of: Milliroentgens per hour Roentgens per hour Milliroentgens per minute Roentgens per minute

Charlie Chong/ Fion Zhang

Q32 Prolonged exposure to heat can effect a: Alarm ratemeter Survey meter Geiger counter Film badge Q33 Which of the following is an example of electromagnetic radiation?

Radio waves Light waves Gamma rays All of the above Q34 Which of the following are the two most common industrial gammaray sources?

Ir 192 and Beryllium 54 Radium and Beryllium Cobalt and Iridium X-ray and Lead

Charlie Chong/ Fion Zhang

Q35 Which of the following has the most material penetrating power?

Iridium 192 Cobalt 60 Cobalt 59 Iridium 191 Q36 The time required for one half of the amount of unstable material to degrade into a more stable material is called: Half-time Half-life Half value layer Half-sign Q37 Which of the following is used to provide a permanent record of radiation exposure?

Alarm ratemeter Survey meter Dosimeter Film badge

Charlie Chong/ Fion Zhang

Q38 Which of the following has the longest wavelength?

Radio waves Proton rays Gamma rays Photon rays Q39 The dislodging of one or more electrons from an atom is called: Ionization Refractology Half-life Isotope Q40 Ionization of living tissue causes: Cells to multiply faster The cells to warm up Molecules in the cells to be broken apart All molecules to explode

Charlie Chong/ Fion Zhang

Q41 What percentage of human exposure comes from outer space, rocks, soil. radon gas and the human body?

20% 40% 60% 80% Q42 Typical industrial radiography pocket dosimeters have a full scale reading of: 50 milliroentgens 100 milliroentgens 200 milliroentgens 400 milliroentgens Q43 Increasing the distance from the source of radiation: Will reduce the amount of radiation received Will increase the amount of radiation received Will not change the amount of radiation received Will result in the need of a slower speed film

Charlie Chong/ Fion Zhang

Q44 All people have radioactive isotopes inside their bodies.

True False Q45 The less time spent near a radioactive source or an x-ray tube: The more dosage the radiographer will receive The higher the rem count The lower the life expectancy The less radiation dose will be received Q46 The primary risk from occupational radiation exposure is the increased risk of: Cancer Blindness Abrasions None of the above

Charlie Chong/ Fion Zhang

Q47 In general, the denser the material: The more radiation is reflected The better shielding it will provide The lower the atomic number The faster the exposure time Q48 How much radiation is a radiographer allowed to receive in a calendar year?

15 rem 10 rem 50 rem 5 rem Q49 The current lifetime risk of dying from all types of cancer in the United States is approximately: 5% 10% 15% 20%

Charlie Chong/ Fion Zhang

Q50 A symptom from an overexposure to radiation which occurs years later is called: Somatic effects Biological effects Latent effects Genealogy effects

Charlie Chong/ Fion Zhang

The Red Line

Charlie Chong/ Fion Zhang

Q9 When radiation interacts with a cell wall or DNA: The cell becomes energized The radiation shifts to a different waveform The cell becomes radioactive The cell either dies or becomes a different kind of cell such as a cancer cell

Charlie Chong/ Fion Zhang

Q20 What percentage of human exposure comes from outer space, rocks, soil. radon gas and the human body?

20% 40% 60% 80%

Charlie Chong/ Fion Zhang

Q2 Which of the following is a rate measuring instrument?

Survey meter Audible alarm Area monitor All of the above

Charlie Chong/ Fion Zhang

Q11 X-rays were discovered in 1895 by: Robert Conrad Marie Curie Pierre Curie Wilhelm Roentgen

Charlie Chong/ Fion Zhang

Q14 How long after the Roentgen’s discovery, were radiation burns detected?

1 day 1 year 1 month 6 months

Charlie Chong/ Fion Zhang

Q1 The most significant source of man-made radiation exposure to the average person is from: Gamma rays Beta rays Medical procedures Alpha rays

Charlie Chong/ Fion Zhang

Q8 If a person received a radiation dose of 10 rem to the entire body (above background), his or her risk of dying from cancer would increase by one percent to a high of: 5% 10% 15% 21%

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Q26 Who discovered natural radioactivity?

Wilhelm Roentgen Marie Curie Henri Becquerel None of the above

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Q49 The current lifetime risk of dying from all types of cancer in the United States is approximately: 5% 10% 15% 20%

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Q50 A symptom from an overexposure to radiation which occurs years later is called: Somatic effects Biological effects Latent effects Genealogy effects

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More Reading http://eesc.columbia.edu/courses/ees/lithosphere/labs/lab12/radioisotope_tutorial.html http://www.iem-inc.com/information/tools/gamma-ray-dose-constants Skyshine: http://www.jacmp.org/index.php/jacmp/article/view/3286/2047 http://mnrc.ucdavis.edu/isotopeproduction.html

Charlie Chong/ Fion Zhang

Charlie Chong/ Fion Zhang

Charlie Chong/ Fion Zhang

Charlie Chong/ Fion Zhang

Good Luck!

Charlie Chong/ Fion Zhang