Introduction on air transport of Dangerous Goods.
-Introduction -Background -Regulations -Limitations -Classification -Class 1: Explosives -Class 2: Gases -Class 3: Flammable liquids -Class 5: Oxidizers -Class 6: Toxic and infectious substances -Class 7: Radioactive material -Identification -Fig. 1 List of Dangerous Goods Packing -Fig. 2 Packing Instruction Packaging, Marking and labeling and Documentation -Fig. 3 Shippers Declaration -Fig. 4 Example of a NOTOC: -Handling and loading -Table 1 Class compatibility -Table 2 Separation chart -Table 3 Compatibility Chart -Table 4 Separation distances for radioactive substances -Emergency and contamination -Dangerous Goods Emergency Chart -Dangerous goods in passenger baggage -Provisions for Dangerous Goods -Carried by Passengers or Crew -Radioactive materials
Background In the early 1950’s, a growing demand was found for transporting hazardous materials and substances by air. Experience from other forms of transportation had shown that, handled correctly, this could be done without risk so long as the goods are suitably packaged and in limited quantities. These experiences, in conjunction with the aviation communities’ knowledge of the characteristics of air transport, resulted in the first industrial regulations on the safe transportation of dangerous goods. Today we know these regulations as IATA Dangerous Goods Regulations (IATA DGR). These regulations are however, based on the requirements of Annexes 18 of the Chicago Convention and the subsequent editions of ICAO Technical Instructions (ICAO TI) which the legal documents are relating to air transport of dangerous goods. IATA DGR applies to IATA member airlines, associate members and interlines partners so, unless operating as such; ICAO TI is the document to comply with. The “core” of all regulations on transporting dangerous goods is the list of hazardous materials and substances as recommended by the United Nations “Committee of Experts” and the “International Atomic Energy Agency”. This list consists of more than 3000 entries describing the hazards and how they are to be handled. Each entry has been assigned a number known as the “UN number” as a form of universal index. As in all potentially hazardous activities, awareness is the key to maintaining safety. In May 1996, the world sadly saw the tragic consequences of insufficient awareness when a DC-9 from Value Jet crashed in the Florida Everglades after hazardous materials had caused a severe fire on-board (picture below). Generally, regulations tend to require relevant training of all staff, ground or airborne, who may encounter dangerous goods with recurrent training every two years.
Regulations The regulations to be adhered to are the previously mentioned ICAO TI and IATA DGR, as applicable, and JAR OPS 1/3 subpart R and various state regulations. State regulations generally do not address specific handling requirements of the various substances that may be hazardous, referring only to ICAO TI in those respects. They do however, regulate operational requirements and limitations. In this document, I mainly refer to IATA DGR and JAR OPS, with some references to
different state regulations. IATA DGR contain all of the requirements of ICAO TI with additional requirements that are more restrictive and reflect industry standards or operational requirements of IATA members. Where ICAO TI concerns ICAO member states and consequently includes state variations, IATA DGR also lists operator variations. For instance, some operators such as Swissair and Cathay Pacific do not accept Gallium for transport as it has a severely detrimental effect on aluminum. Dangerous goods are defined as articles or substances which are capable of posing a significant risk to health, safety or to property when transported by air. When we discuss dangerous goods in this context, we generally mean cargo, as dangerous goods are prohibited in passenger baggage, with a few exceptions. Hazardous substances in passenger baggage can however, pose a greater threat to air safety than cargo as they may easily find their way onto an aircraft unnoticed. The travelling public cannot be expected to have the knowledge of the characteristics of air transport that professionals in the industry have, or even of the potential dangers of articles they carry in their baggage. Therefore, it is the responsibility of all staff involved in passenger and dead-load handling, as well as aircrews, to be vigilant to signs of potential hazards. The operator has the final responsibility to make sure the passengers and or client is informed and aware of regulations and technical instructions. In our operation the aircrew will do this by using the list of goods on page ….
Limitations Articles and substances classified as dangerous goods have various limitations imposed on then depending on how dangerous they are. Some goods are considered too hazardous to transport by air while others may be limited to transport on cargo aircraft only and some may be acceptable on both cargo and passenger aircraft. Certain dangerous goods normally not acceptable for transport by air may be transported under exemption by the state of origin, the state of destination and all states to be over-flown.
Dangerous goods forbidden in aircraft under any circumstances: • Explosives which ignite or decompose when subjected to a temperature of 75ºC (167ºF) for 48 hours. • Explosives containing both chlorates and ammonium salts.
• Explosives containing mixtures of chlorates with phosphorous. • Solid explosives which are described as extremely sensitive to mechanical shock • Liquid explosives which are described as moderately sensitive to mechanical shock. • Any article or substance, as presented for transport, which is liable to produce a dangerous evolution of heat or gas under the conditions normally encountered in air transport. • Flammable solids and organic peroxides having, as tested, explosive properties and which are packed in such a way that the classification procedure would require the use of an explosives label as a subsidiary risk label. The dangerous goods listed in table 2.1A of IATA DGR (this is a long list and therefore not reproduced here). Dangerous goods forbidden unless exempted: 1. Radioactive material which is: • in vented type B(M) packages • in packages which require external cooling by an ancillary cooling system • in packages subject to operational controls during transport 2. Explosive 3. a pyrophoric liquid. 4. Unless otherwise provided, articles and substances (including those described as “not otherwise specified”) which are identified in the List of Dangerous Goods as being forbidden. 5. Infected live animals. 6. Liquids having a vapor inhalation toxicity which requires Packing Group I packaging. 7. Substances that are offered for transport in a liquid state at temperatures equal to or exceeding 100ºC (212ºF), or in a solid state at temperatures equal to or exceeding 240ºC (464ºF).
Limitations on dangerous goods acceptable for air transport are to be found in the lists based on the recommendations of the Committee of Experts in IATA DGR or ICAO TI. A permanent approval is required in order for an operator to be allowed to carry dangerous goods with the exception of four instances. These are: 1. Articles and substances required for the airworthiness of the aircraft. 2. Catering or cabin service supplies. 3. Veterinary aids or humane killers for animals. 4. Medical aids for a patient. Under 1), we find such things as oxygen and fire extinguishers. Point 2) includes such things as dry ice and alcohol (whiskey is classified as dangerous goods). There are many articles which fall under 4), the most common being oxygen or compressed air and electric wheelchairs. The Universal Postal Union prohibits all dangerous goods in airmail with two exceptions. • Infectious substances may be accepted, provided the consignment is accompanied by a “Shippers Declaration” and it may be refrigerated with dry ice. • Radioactive material may also be accepted if it has very low activity. Very small quantities of dangerous goods may be transported in such a manner that they may be excepted from the marking, labeling and documentation requirements. This
is known as “Dangerous goods in Excepted Quantities” and is only applicable to goods acceptable on passenger aircraft. The following provisions must also be met: Substances of division 2.2 without a subsidiary risk. Substances of class 3, all packing groups. Substances of class 4, packing groups II and III but excluding all self-reactive substances. Substances of division 5.1, packing groups II and III. Substances of division 5.2, only when contained in a chemical kit or first aid kit. Substances of division 6.1, all substances in this division, except those having an inhalation toxicity requiring packing group I. Substances of class 8, packing groups II and III but excluding Gallium and Mercury. Substances and articles of class 9, other than magnetized material The concept “excepted quantities” can not be applied to passenger baggage or airmail. There is also an extensive list of goods not acceptable as cargo in excepted quantities. I have not included this list here because it basically lists the opposites of the above list. When we speak of “very small quantities” we are dealing with, for instance, 1g or 1mL for solids or liquids of packing groups I or II in division 6.1 or requiring a subsidiary toxic label, or 30g or 30mL for other substances. For non-flammable gases with no subsidiary risk we are limited to receptacles with a water capacity of 30mL. The combination of packages in an outer package allows, with a few exceptions: Packing group I – 300g or 300mL. Packing group II – 500g or 500mL. Packing group III – 1L or 1kg. Always refer to ICAO TI or IATA DGR for details. Though excepted quantities do not require the regular labeling of dangerous goods they do require labels stating that they are “Dangerous Goods in Excepted Quantities” stating class and UN-number of the contents. When packing these goods it is not necessary to use the approved packages normally required for dangerous goods. It is sufficient to use “good quality” packaging according to the specifications in the regulations. For inner packaging, they should be constructed of plastic, glass, earthenware or metal. The regulations also allow for “Dangerous Goods in Limited quantities”. All this means is that some forms of dangerous goods may be packed in simpler, though good quality, packages if the quantity is less than a given amount. I have not provided a list of substances allowed in limited quantities here because, though it is not long it is fairly detailed. These goods still need to be marked, labeled and documented as dangerous goods. The net amount allowed as limited quantities is specified in the List of Dangerous Goods along with packing requirements. The gross weight of a limited quantity package must however, not exceed 30kg. I will clarify the difference under the section “Identification”.
Classification Dangerous goods are divided into nine classes depending on the type of hazard they pose, while the three packing groups relate to the degree of hazard. Some classes are divided into divisions as there may be several types of substances with the same type of hazard. Gases, for instance, can be toxic, flammable or non-toxic and non-flammable. Class 1: Explosives Explosives are defined as: • Explosive substances except those whose predominant hazard should be in another class. • Explosive articles, except devices containing explosive substances in such a limited quantity or of such a character that their inadvertent or accidental ignition or initiation, during transport, will not cause any manifestation of projection, fire, heat, smoke or loud noise external to the device. • Other articles or substances which are manufactured with a view to producing a practical explosive or pyrotechnic effect. Division 1.1 Explosives having a mass explosion hazard
Division 1.2 Explosives having a projection hazard but not a mass explosion hazard
Division 1.3 Explosives having a fire hazard, a minor blast hazard and/or a minor projection hazard but not a mass explosion hazard.
Division 1.4 Explosives presenting no significant hazard.
NOTE: Class 1.4S is the only explosive acceptable on passenger aircraft.
Division 1.5 Very insensitive substances having a mass explosion hazard.
Division 1.6 Extremely insensitive substances that do not have a mass explosion hazard.
Class 2: Gases In this class, we find compressed and liquefied gases, and refrigerated liquefied gases. Also gases in solution, mixtures of gases and mixtures of gases with vapors of other substances. Articles charged with a gas and aerosols also belong here. Division 2.1 Flammable gas.
Division 2.2 Non-flammable, non-toxic gas.
Division 2.3 Toxic gas.
Class 3: Flammable liquids This class has no divisions. It comprises liquids, mixtures of liquids and liquids containing solids in solution or suspension, which give of a flammable vapor.
Class 4: Flammable solids This class has no divisions. It comprises liquids, mixtures of liquids and liquids containing solids in solution or suspension, which give of a flammable vapor.
Division 4.2 Substances liable to spontaneous combustion.
Division 4.3 Substances that, in contact with water emit flammable gases.
Class 5: Oxidizers Oxidizers are substances which, though not necessarily combustible in them-selfe, may cause or contribute to combustion in other materials. Division 5.1 Oxidizer.
Division 5.2 Organic peroxides.
Class 6: Toxic and infectious substances This class includes substances which are liable to cause death, injury or to harm human health if they are swallowed or inhaled, or by skin contact. Division 6.1 Toxic substances.
Division 6.2 Infectious substances.
Class 7: Radioactive material This class has no divisions but is possibly the one that there is the most to be said about. Therefore, I have devoted an entire section to this class alone. For the purpose of regulations, a radioactive material is any substance with a specific activity greater than 70 kBq/kg.
Class 8: Corrosives This class has no divisions. It comprises substances that can cause severe damage by chemical action when in contact with living tissue, other materials or the aircraft.
Class 9: Miscellaneous dangerous goods This class covers all articles and substances that are not covered by other classes, and includes magnetic material. Some examples are: � Asbestos � Carbon dioxide, solid (dry ice) � Environmentally hazardous substances � Life-saving appliances � Internal combustion engines � Polymeric beads RMD RSB ICE � Battery powered equipment or vehicles and many others…
Subsidiary risk labels Some hazardous substances may have properties that would place them in more than one class or division. Such substances must carry a label showing the subsidiary hazard as well as the primary hazard.
Handling labels for dangerous goods Labels with arrows indicate that the package must be secured with the indicated direction upwards. CAO indicates that the package may only be loaded on cargo aircraft. Explosives are also assigned to compatibility groups indicated by the letters A to S. A division of explosives may belong to several compatibility groups and each compatibility group can cover several divisions of explosives. There are three packing groups indicating the degree of hazard a substance or article may present. � Packing group I – great danger. � Packing group II – medium danger. � Packing group III – minor danger.
Most substances have been assigned a packing group based on technical criteria, some however have been assigned based on experience. It is the Shipper’s responsibility to ensure that an article or substance is identified and classified correctly and that it is asked in compliance with the relevant regulations. The operator must comply with the requirements for acceptance, storage, loading, inspection, provision of information, emergency response, retention of records and training. The crew will use the checklist issued by IATA to carry out an acceptance check on Dangerous Goods. This checklist is enclosed in this compendium as an annex.
Identification In order to make life a little easier for those of us, who are not well versed in chemistry or nuclear physics, dangerous goods are assigned what is known as a “proper shipping name n.o.s.” (not otherwise specified). In many cases, it can be impractical or of little value to show a long and complicated name on an air waybill or NOTOC, then it is more useful to use the generic or n.o.s. proper shipping name. An example listed in IATA DGR is methyl-n-amyl carbinol. This is an alcohol with a flashpoint of 54ºC and is not listed by name. As the scientific name is meaningless to most pilots and cargo handlers, the proper shipping name is more relevant. The most descriptive name is “Alcohol n.o.s.” which is what we will find on all the documentation. It is however, good practice and encouraged, to add the full name in parenthesis on the documentation. For the same purpose, we also use the UN identification numbers as assigned by the “Committee of Experts”. By using these numbers for cross-reference all qualified personnel can easily identify the goods and its’ associated hazards. In an emergency, it can be a clear and concise way of informing rescue teams of what they will encounter. Let us look at another example to illustrate all the strange new vocabulary. We want to send two shipments that may be dangerous goods. One is a very large bottle of whiskey and the other is a bottle of Stroh rum. The volume of our whiskey bottle is 5 liters and the alcohol content is 43% by volume. The Stroh rum is also 5 liters but 80% alcohol. When we look in section 4 of IATA DGR, we find the following entries in the list of dangerous goods:
Since our bottle of whiskey is only 5L, it can be shipped as “Limited quantity” as this allows up to 10L. It must be packed according to packing instruction Y309 which is somewhat simpler than that required for receptacles of more than 10L. Although we can send it as “Limited quantity” it still needs all the labels and documentation required for dangerous goods. Receptacles of less than 5L are not restricted at all. “Excepted quantities” is not applicable since these are limited to 1L in the case of flammable liquids. Our bottle of Stroh rum, on the other hand, is too much for “Limited quantities” and so needs the full treatment. If it had been 1L or less we could send it as “Limited quantities”. If we were sending only 30mL of Stroh rum we could send it as “Excepted quantities” in which case our package would not need to be labeled as “Flammable liquid” or documented as dangerous goods. It would only require an “Excepted quantities” label. We will return to these two examples further on. Packing The packing of dangerous goods is almost a science in itself. To begin with, we will discuss the various ways of packing and shipping cargo. There is, of course, the simple package containing the dangerous substance and nothing else. But then life is seldom so simple. If the dangerous substance or article is not alone in the package, we have what is known as an outer package. The package may be grouped together with other packages in an overpack or it may be loaded together with other cargo in a container or ULD (Unit Load Device). All these different ways of packing imply different conditions that need to be addressed in marking, separation and loading. A primary concern is to ensure that different forms of dangerous goods are kept apart if they do not agree with one another. Some forms of explosives, for instance, should not be loaded or packed together. When we looked at our examples, above, we saw references to packing instructions. These are comprehensive instructions on how the substance or article must be packed, including the materials to be used in the package and provisions for ventilation, shock absorption etc. Our bottle of whiskey, shipped as “Limited quantities”, refers to packing instruction Y309. This instruction tells us, to begin with, that if the bottle is made of glass it is too big. If we use glass, we are only allowed to have 2.5L in each package. Plastic and metal
receptacles may contain 5L. We also find that our whiskey must be packed in a sturdy outer package with sufficient cushioning and absorbent material to prevent movement and leakage. The table below is a partial replication from packing instruction Y309.
In this table we can see that there are a number of outer packaging’s to choose from. The Stroh rum must be packed according to packing instruction 305 which has a table similar to the one above with a few differences. Glass and earthenware is limited to 1L and the outer packagings refer to specification codes. These codes are found in the regulations and give fairly detailed descriptions on how the package is to be constructed and tested. Packaging We have seen that the aspects to consider in handling dangerous goods are, mainly, the type and degree of hazard. We also have to consider the particular properties of the substance or article we are shipping. Flammables, for instance, have different flash points, toxins are harmful in different ways (inhaling, skin contact etc.) and explosives can be ignited in different ways. All these aspects are important to consider when selecting a suitable package but they are not quite enough. The conditions under which the package is going to be handled are also a factor as well as, possibly, storage in transit and conditions at the destination. Some countries and airlines also deviate from the regulations in their requirements. Dangerous goods must always be transported in approved packages unless they are acceptable in “Excepted quantities” or “Limited quantities”, or if they are not restricted. Approved packages are recognized by the UN mark.
This mark is always followed by a number of codes signifying type, packing group,
limitations, year of manufacture etc. The mark implies that the construction of the package corresponds to a design type that has been tested according to specifications set down in the regulations. The tests are definitely not kind to the packages. They are required to survive drops, heating, drowning, punctures and many other forms of torture. Marking and Labeling The correct marking and labeling of dangerous goods is very important. It may be the clearest way of identifying a package containing dangerous goods in a stressful environment, especially if the package has been damaged and there is risk of contamination. Under the section “Classification” I have included a complete set of the labels to be used along with the classes and divisions they represent. My personal “favorite” among dangerous goods classes is infectious substances. Anyone encountering such a package that is spilling its’ contents has, most likely, already been infected, unless he sees it at a safe distance. If the package has been damaged during flight, the person opening the cargo hatch will find himself in close proximity to it before he sees the danger. While this is also true for toxins with an inhalation hazard, most other forms of dangerous goods can be found, damaged, without significant personal danger. For these reasons, if nothing else, no dangerous goods may be loaded on an aircraft with damaged or missing labels Documentation There are three documents that must accompany all forms of dangerous goods shipped as air cargo, except those shipped as “Excepted quantities”. The first is the “Air Waybill”.
While this should be completed for all air cargo, if the consignment includes dangerous goods, the “Air Waybill” must include all relevant hazard information.
Next, we have the “Shippers Declaration for Dangerous Goods”. This must include the following information: � Shipper � Consignee � Air Waybill number � How many pages � Aircraft limitations: “Passenger and cargo aircraft” or “Cargo aircraft only” � Airport of departure � Airport of destination � Shipment type: “Radioactive” or “Non-radioactive” � Nature and quantity of dangerous goods � Additional handling information (special handling requirements) � Name and title of signatory � Place and date � Signature The lower half of the “Shippers Declaration for Dangerous Goods” (fig.3) concerns nature and quantity, and is reproduced in part below:
NOTE: The actual document is easily recognized by its’ borders in red hatching. This data is to be copied to the third document known as the NOTOC (fig.3) (Notification To Captain). This document is completed by the shipper or handling agent and is signed by the person responsible for loading the aircraft, and given to the captain. The format of a NOTOC may vary, in detail, from airline to airline but they basically cover the same information. The purpose of the NOTOC is twofold. It is a legal document whereby the person responsible for loading the aircraft certifies that the regulations have
been complied with and it serves to inform the pilot in command of what has been loaded, how and were.
All those documents must be issued with minimum 3 copyâ€™s. 1. Captain, Operator, 2 Originator, 3 Receiver Handling and loading Last in the chain of handling dangerous goods is the person responsible for loading the aircraft, whether it is a handling agent or one of the pilots. Distributing the load in the aircraft may require some thought and planning, particularly if there are other special loads involved such as live animals or foodstuffs. As we have seen some dangerous goods must be kept apart from each other but we must also consider other special loads. There are various ways of separating different forms of cargo depending on if the aircraft is ULD-loaded or bulk-loaded, or a combination of the two. Some things must be loaded in separate compartments while others only need to be kept well apart. Dry ice emits carbon dioxide, which is suffocating so it must not be loaded in the same compartment as live animals or they may not reach the destination alive. Radioactive materials may be loaded in the same compartment as live animals as long as there is sufficient distance separating them to prevent the animal from being contaminated. Another situation is live animals and infectious substances. These may not be loaded in the same compartment or on adjacent pallets but may be loaded in adjacent, enclosed containers.
Before accepting a package of dangerous goods for loading, the person supervising the loading must inspect the goods to make sure the packages or labels are not damaged. He must also make sure all the documentation is in order and that the goods are loaded and secured safely. His signature on the NOTOC must be a trustworthy guarantee for the crew who are taking the hazard with them into the air. The following tables are of some aid in planning the loading of dangerous goods on an aircraft.
NOTE: Group 4.1 and classes 6, 7 and 9 are not included in this table, as they do not require separation from other classes of dangerous goods. NOTE 1: Explosives of the same compatibility group may be loaded together regardless of division. NOTE 2: Only explosives of division 1.4S may be loaded with this compatibility group. Explosives not belonging to the same compatibility group may not be loaded together even if they belong to the same division, with the exceptions of compatibility groups C, D and E which may be loaded together. Explosives of division 1.4S may be loaded together with other compatibility groups with the exceptions of compatibility groups A and L.
Table 2 Separation and Compatibility Chart
Indicates packages that must be separated, physically, from one another, either in separate compartments or secured well apart.
Minimum separation distance in accordance with IATA DGR. May not be loaded together. Adequate separation distance. May not be loaded in the same compartment; may not be loaded on adjacent pallets. May be loaded in adjacent, enclosed, containers. May not be loaded in the same compartment. Separation is only required for laboratory animals and animals that are natural enemies. Table 4 Separation distances for radioactive substances. Minimum distance between the surface of a package, “Overpack” or container, and the floor of the cabin or flight deck, or live animals.
Emergency and contamination If a package of dangerous goods has been damaged to the extent that it spills its contents, the situation must be handled promptly and correctly. Regardless of the nature of hazard everyone not immediately required in the vicinity must be kept well away. Anyone who may have been affected (harmed or contaminated) must be taken care of and their names and addresses noted. The person supervising the situation must consult a suitable “Dangerous Goods Emergency Chart” (ICAO Doc. 9481) to see what immediate remedial action may be required. The wrong action may make the situation worse. As soon as possible expert help must be acquired. There are seldom any established official channels for this, the local telephone directory is usually the best way of getting expert help. In the case of leaking toxins, for instance, one could simply call the nearest hospital and get help from their toxicologists. All handling agents should have an emergency chart, similar to the one below, readily available together with types of procedures and kits to handle this type of emergencies.
Dangerous Goods Emergency Chart
Dangerous goods in passenger baggage Dangerous goods, as such, are not permitted in passenger baggage. Passengers do however, often pack articles and substances that are hazardous. To a certain extent, this is acceptable. It would not be proper to discriminate against disabled passengers who need electric wheelchairs so these are allowed. Some forms of cosmetics such as hairspray and perfume may be hazardous but it would be very difficult to get passengers to abstain from bringing these on their journeys. On the next page there is a table taken from IATA DGR that indicates what is acceptable and to what extent. The major problem in this case is to locate the passenger who is carrying unacceptable articles. It is mainly up to passenger handling staff to be on the lookout for signs of potential hazard as it would be unethical or illegal to search the baggage.
These are a few suggestions: Camping or hiking equipment. May contain butane or flammable liquids, an extensive supply of matches, emergency flares and many other dangerous articles. Toolboxes. Some forms of measuring equipment are radioactive. There may be gaspowered soldering irons, explosives, adhesives, corrosives, resins, paints solvents etc. Diving equipment. Apart from the breathing apparatus, divers may be carrying diving torches that generate extremely high heat when operated in air. Motion picture and stage. May involve articles for special effects that may contain explosives or flammables. Automobile accessories. Substances for corrosive protection. Fuel additives such as nitro methane. Most passengers cannot be expected to be familiar with the normal conditions in an aircraft such as the changes in temperature and pressure. Nor can they be expected to always consider the dangers inherent in the everyday objects we all surround ourselves with. A large supply of matches on a pantry shelf does not seem particularly lethal but packed in a bag on board an aircraft it can be very hazardous. Information about dangerous goods in baggage must be provided to the passengers. As a minimum, this must consist of placards at check-in counters and having it printed on tickets or ticket folders. Though it might prove difficult or impractical in a congested situation it is good practice for all check-in staff to ask each passenger if they are carrying any of the articles on these placards.
Radioactive materials Radioactive packages can be very unpleasant to handle. Radiation cannot be detected by any human senses, only by measuring equipment. Nevertheless, it can be very harmful to living tissue and organs. The smallest, noticeable, symptoms of radiation contamination are nausea and vomiting, and a generally unpleasant feeling. These symptoms disappear within a couple of days. The worst symptoms are much more gruesome. The radiation can destroy the central nervous system and most of the internal organs leading to death within two to three days. Radioactive materials are articles or substances that spontaneously and continuously emit-ionizing radiation. These substances are composed of one or more of the chemical elements and each is distinguished by its own unique atomic number. The atoms of each chemical element can exist in a number of slightly different variations without altering the chemical characteristics or the physical form of the element. Some of these variations occur naturally and some are artificially produced and are termed isotopes or nuclides. Each of these is denoted by its own atomic mass number, not to be confused with atomic number. For instance, Chlorine has the atomic number 17 and as isotopes may be called Chlorine-35 or Chlorine-37 which are non-radioactive or, Chlorine-36 or Chlorine-38 which are radioactive and so termed radioisotopes. Radioactive substances consist of material in which at any particular time some of the atoms are radioactive. Each of these radioactive atoms, randomly and spontaneously, undergoes a process of disintegration. In this process the atoms emit their characteristic form of radiation and decompose into another configuration. This radiation consists of one or more of the various forms of radiation, alpha, beta, gamma, X-ray or neutron. We are, to some extent, interested in measuring the activity of the radiation. The old unit of measuring activity was the Curie (Ci) but the SI unit is the Becquerel (Bq) which is defined as one atomic transformation per second. Since the Becquerel is such an extremely small unit, it is common to use the multiples kilo Becquerel (kBq) or mega Becquerel (MBq). For the purpose of dangerous goods regulations a substance must have an activity greater than 70 Becquerel per gram (70 Bq/g) or 70 kilo Becquerel per kilogram (70 kBq/kg) to be regarded as radioactive material. The activity of a radioactive material is, essentially, a measurement of its quantity. As each radioactive atom decays the remaining activity declines. The time it takes for a radioisotope to lose half its activity is known as its half-life. In successive half-life periods, a radioisotope is reduced by decay to Â˝, Âź, etc. of its initial value. It is therefore possible to predict the remaining activity at any given time. The half-life time may be significant when transporting radioisotopes with extremely short half-lives. The half-life period may vary from billionths of a second to billions of years. The different forms of radiation, mentioned earlier, have varying characteristics. Alpha radiation has a range of a few centimeters, in air, and beta radiation has a range of a few meters. These can generally be absorbed by paper or wood, or conventional packing materials. Gamma and X-ray radiation, on the other hand, have theoretically infinite ranges and are only absorbed by high-density materials such as lead. They do however, disperse rapidly with distance. For our safety we are interested in measuring radiation exposure and radiation dose equivalent. The old units of measurement were roentgen ( R ) and ream, respectively. The SI unit of radiation exposure is Coulomb per kilogram (C/kg) and for dose-equivalent it is Sievert (Sv). Neutron radiation is a special case. It is assessed, primarily, by the number of neutrons passing through unit cross-sectional area in unit time. This can be converted to dose equivalent by a fairly simple method.
There are international agreements on acceptable levels of radiation in a working environment. These are usually established in terms of cumulative doses on a yearly basis and applied as limiting dose-equivalent rates. This means that an environment where a person is constantly exposed to radiation will be limited to a lower doseequivalent rate than an environment where radiation is more sporadic. Another safety consideration, in a working environment, is the form of the radioactive substance. A radioactive gas or liquid may find its way into the body where it will stay for varying lengths of time. How long will vary depending on the form and characteristics of the substance. Some substances will be rejected by the body immediately while some are retained indefinitely. In the latter case the dose-equivalent rate may be low but since the exposure time is likely to be for life the accumulated exposure will be severe if the substance has a long half-life period. Fissile materials are radioactive materials in which the atoms can be split by neutron radiation which will cause them to release energy in the form of heat, gamma radiation and more neutron radiation. If a sufficient quantity of fissile material is assembled in one place under certain conditions the added neutron radiation can cause a nuclear chain reaction. This kind of reaction is known as critical and may produce intense heat and high radiation. More or less what happens in an atomic bomb. For the purpose of dangerous goods regulations only the following radioisotopes, or mixtures containing them, are considered fissile: � Uranium-233 � Uranium-235 � Plutonium-238 � Plutonium-239 � Plutonium-241 The regulations go into further detail which are worthwhile reading if one should come into contact with the transport of fissile materials. Some other terms used in the transport of radioactive material are “Special form”, “Surface Contaminated Objects” (SCO) and “Low Specific Activity” (LSA). “Special Form” is used to describe radioactive material which is in a sealed integral form and so cannot, for all practical purposes, produce radioactive contamination. “Surface Contaminated Objects” is more or less self-descriptive. This is an object which is not radioactive in it but has radioactive material on its surface. “Low Specific Activity” is material that, by nature, has limited activity or for which limits of estimated average activity apply. When transporting radioactive materials it is impractical to go into the details of the various forms of substances and their different forms of radiation. The packages, or over packs, are assigned to one of three categories known as: � “category I-white” or “RRW” � “category II-yellow” or “RRY II” � “category III-yellow” or “RRY III” Which category a package should be assigned to is determined, primarily, by measuring its surface radiation. “Category I-white” is limited to 5 μSv/h, “category II-yellow” allows up to 0.5 mSv/h and more than that but less than 2 mSv/h is assigned to “category IIIyellow”. Depending on the size of the package and the radiation it emits, a transport index (TI) is determined. The purpose of this is to enable us to handle it correctly without having a deep knowledge of nuclear physics. Using table 4 above we can fairly easily determine where, in an aircraft, we can load the
package and to what extent we need to ensure it is separated from other cargo. If, for instance, we receive three packages with TI of 2, 3 and 3.5 respectively we can see that they must be separated from live animals, cabin floor (or walls) and some other forms of cargo. The first two packages must have a minimum separation of 70cm and the third 85cm. If, however, we load all three packages in the same place we get an accumulated TI of 8.5 which requires a separation of 155cm. When receiving an aircraft carrying radioactive materials one always approaches the hold while measuring the radiation levels. As long as the instrument one is using shows no significant radiation, it is safe to proceed up to the cargo hatch. After that, open the hold and measure inside the hold. If the package appears undamaged, measure the surface of the package and if there is still no more radiation than expected, it is safe to unload the package. If, at some point in the procedure, the radiation levels increase significantly it is imperative to stop and back away. Get qualified assistance and let them handle the situation. Refer to the chapter on emergencies and contamination.