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
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
Natural background 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
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.
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.