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What is radiation? ď Ź Energy emitted from source travels in straight line through medium or space. ď Ź Two types: 1) non-ionizing radiation 2) ionizing radiation (produce charge particle)


Non-ionizing radiation Light

Radio Radio

Non-ionizing Non-ionizing radiation radiation



Ionizing radiation ď Ź Radiation that can disrupt the atoms and the molecule within the body. ď Ź When radiation with enough energy interact with an atom, it can remove tightly bond electrons from the orbit of an atom, causing the atom to become charged or ionized.


ď Ź Sources of radiation: Natural background radiation : Man-made radiation


NATURAL RADIATION  Also known as background radiation.  This type of radiation exist from million of years before.  It is impossible to decide whether the natural background radiation has been harmful or beneficial to the development of the human species.  This natural background radiation comes from three main sources: cosmic radiation,  terrestrial radiation, and  internal radiation. 6

Ionizing radiation

Natural background radiation

Cosmic radiation

Terrestrial radiation

Internal radiation




Cosmic Radiation  Cosmic radiation originated from the extraterrestrial (outer space).  It is composed of a very wide range of penetrating radiations which undergo many types of reactions with the elements they encounter in the atmosphere.  The atmosphere acts as a shield and reduces the amount of cosmic radiation reaching the Earth’s surface  This filtering action means that the dose rate of cosmic radiation at sea-level is less than at high altitudes.





Terrestrial Radiation  The rocks and soil of the Earth’s strata contain small quantities of the radioactive elements such as uranium and with their daughter products (thorium, radium, and radon).  The concentration of these elements varies considerably depending on the type of rock formation.  In sandstone and limestone regions the concentration is much lower than granite.  Thus the dose rate from this source depends on the geographical location. 14

Ionizing radiation

Terrestrial radiation



Radioactive material found in:




Radioactivity in The Body (internal radiation)  The human body contains very small quantities of the radioactive isotopes carbon -14 potassium-40 and polonium-210.  The C-14 originate in the atmosphere and results in a dose of 10 μSv/year in the soft tissue.  K-40 is naturally-occurring and contributes about 0.2 mSv/year to the gonads. 17

 Contribution to the radioactivity in the body comes from the gaseous decay products of the uranium and thorium radioactive series (radon and thoron).  These gases diffuse from the rocks and soil and are present in easily measurable concentrations in the atmosphere.  They are breathed by man along with their decay products and are also taken up by plants and animal.


Ionizing radiation

Internal radiation





ARTIFICIAL OR MAN-MADE RADIATION  The early experiences of man-made sources of radiation involved x-rays and various uses of radium.  In addition to the natural background radiation, there are several other sources of human exposure.  These sources are: (a) diagnostic radiology (b) therapeutic radiology (c) use of radioisotopes (d) radioactive waste (e) fall-out from weapons testing (f) occupational exposure 20

Diagnostic Radiology  It has been estimated that 75 – 90% of the total exposure of the population from medical uses of radiation comes from the diagnostic use of x-rays.  The most critical regions of the body are the bone marrow, the gonads, the lens, and the fetus.



Therapeutic Radiology ď Ź In most countries the average dose to the population from therapeutic radiology is much less than that from diagnostic radiology. ď Ź Although quite large exposures may be used in certain treatments, only a small number of people are involved.



Use of Radioisotope in Medicine ď Ź Radioisotopes are used in medicine to give a means of tracing the path and location of specific chemicals in the body. ď Ź Since radioactive isotopes are chemically identical to stable isotopes of the same element, they will follow the same path and be concentrated to the same degree as the non-active isotopes in the body. ď Ź By counting methods the location of the active, and hence of the ordinary non-active, isotopes of the elements may be determined. 25


Radioactive Waste ď Ź The increasing use of radioisotopes and, more particularly, the development of the nuclear power industry results in an ever-growing quantity of radioactive waste. ď Ź Continued dispersal of low and intermediate levels of radioactive waste to the environment means that members of the general population will receive an increasing exposure from this source.



Fall-Out From Weapons Testing  The nuclides of concern in radioactive fall-out from nuclear weapons testing are similar to those arising from the operation of nuclear power stations.  Some of the radionuclide created during a nuclear test are injected into the troposphere (40 000 – 60 000 feet) and are carried around the Earth several times.


14 years old victim


ď Ź Photo of a deadly burnt victim taken in Hiroshima on August 7th, 1945,this young man was located at the moment of the explosion on an island 3000 meters from the hypocenter. Source : Hiroshima Peace Memorial Museum.


Nagasaki aftermath 32

A victim in Nagasaki 33

Occupational Exposure ď Ź Individuals may be exposed to radiation in the course of their occupation involving radiation sources. ď Ź Radiation of artificial origin is widely used in he industry for manufacturing process and quality control, as research tools in universities and research institutions and nuclear industries.



Consumer Product ď Ź Products that have the luminescence material to produce luminance, such as watch, aircraft tools, etc. ď Ź Electrical and electronic equipments: (a) bulb and electronic tube (radioactive materials are used to start the pre-ionization within the gas in order to allow the electric current flowing faster. (b) smoke detector used the alpha radiation to produce ionizing electrical current. 36


Other Products  Porcelain that been used in dental treatment contains uranium.  Ceramic with varieties of colour contains uranium oxide and natrium uranite for the pigmentation.  Colour screen television generates x-rays by the Bremsstrahlung radiation.



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source of radiation