Sources of radiation Sources of radiation exposure

Sources of radiation

Sources of radiation exposure to people population

Background radiation Terrestrial radioactivity Cosmic radiation Internal radioactivity

Terrestrial radiation: external and internal exposure U-238 Ra-222 Th-232 Ra-220

Radon is a gas It is naturally occurring You can not see or smell it It enters buildings from the soil beneath them Radon 3. 8 days Radium 1, 600 years 4. 5 billion years 19 March 2018 Uranium 5

Radon Decay product of radium Estimated to be the second leading cause of lung cancer Nearly one in 15 homes in the U. S. has a high level of indoor radon 6

Radon diffusion from soils Rn is a gas, and can easily leave rocks and soils through fractures /openings into pore spaces between grains of soil. If Rn can move easily in the pore space, then it can travel a great distance before it decays, and it is more likely to collect in high concentrations inside a building. Method & speed of Rn's movement controlled by water in the pore space (the soil moisture content), pore space in the soil (the porosity), and "interconnectedness" of pore spaces that determines the soil's ability to transmit water and air (called soil permeability). 19 March 2018 7

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Radon Movement into Homes Most houses draw less than one percent of their indoor air from the soil; remainder comes from outdoor air, which is generally quite low in radon. Houses with low indoor air pressures, poorly sealed foundations, and several entry points for soil air, however, may draw as much as 20 percent of their indoor air from the soil. Even if the soil air has only moderate levels of radon, levels inside the house may be very high. 19 March 2018 9

High background areas

Cosmic radiation

Internal radioactivity Radioactivity in diet • potassium-40 • lead-210 • polonium-210

Background radiation Air Cosmic - 0. 3 m. Sv Terrestrial - 0. 3 m. Sv Radon - 2 m. Sv Food - 0. 4 m. Sv

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Natural background radiation doses in Europe Naturally occuring background levels of radiation can typically range from 2. 0 to 4. 0 m. Sv a year

Artificial sources of ionizing radiation Radioactive sources Electric generators of ionizing radiation Activities using nuclear energy: Ø nuclear weapons Ø nuclear reactors

Radioactive sources are present in the sealed (normally non spreadable) and unsealed form (spreadable): Gammagraphy essentially uses as sources iridium-192 and sometimes cobalt-60 Neutrongraphy uses sources of neutrons like californium-252 or an americium/beryllium couple. Betagraphy uses beta sources like carbon-14. Chemical and biological radiation-treatment uses gamma radiation sources cobalt-60 or caesium-137.

Radioactive sources in medicine In medicine there are three uses for non-sealed radioactive nuclides: Biological analyses: radio-markers have been replaced progressively by non-radioactive markers. Medical imaging: nuclear medicine department use radio-pharmaceuticals for diagnostics, which are ingested by the patient to obtain an image of the tissue or organ while it is functioning. Therapy: radio-pharmaceuticals can constitute the treatment itself, for example iodine 131 for the treatment of thyroid cancer.

Electric generators of ionizing radiation The industrial applications of electric generators of ionizing radiation are neighbors of radioactive sources. Medical applications comprise radio-diagnostics and radiotherapy: v Medical radio-diagnostics is man’s largest source of exposure to ionizing radiation. It uses standard radiography equipment and X-scanners. v The electric generators used in radiotherapy are electron accelerators of medium energy (20 million volts) which enable a beam of electrons or X-rays to be obtained. In the research sector the large accelerators and scientific instruments are used to study the fine structure of matter.

Effective doses from medical exposure Effective dose (m. Sv) Equivalent period of natural radiation Radiography Chest 0. 02 3 days Pelvis 1. 0 6 months IVP 4. 6 2. 5 years Barium studies 9. 0 4. 5 years CT (Chest, Abdomen) 8. 0 4 years Nuclear Medicine Thyroid imaging 1. 0 6 months Bone imaging 3. 6 1. 8 years

Nuclear Weapons 19 March 2018 21

Nuclear weapons can function by two very different modes – nuclear fission or nuclear fusion: Fission arms employ the principle of an uncontrolled chain reaction, i. e. each fission reaction leads to several further fission reactions Fusion arms (thermonuclear) use the fact that the union of deuterium and tritium to form a single nucleus of helium liberates a very large amount of energy

Extensive above ground testing in US and USSR 1946 -1962 Above ground testing by other countries Waste generated from weapons grade uranium and plutonium production spent nuclear fuel --- processing to enrich U and Pu generates large amount of other radionuclide "waste" which has to be "discarded" -- buried? stored? 19 March 2018 23

Summary number of explosions of nuclear weapons from 1945 to 1998 Country USA 1945 – 1992 Number of explosions 1030 Russia 1949 – 1991 716 France 1960 – 1997 210 Great Britain 1950 – 1960 44 China 1964 – 1996 45 India 1974, 1998 6 1998 5 Pakistan Years

Radionuclide behavior -- Iodine and Cesium Nuclear Reactor Waste & Atomic Bombs Radioactive nuclear fisson products Cesium – 137 Cs+ Iodine - 131 19 March 2018 131 I 25

Uranium Underground and open pits – In situ leaching has been used – radon & gaseous products a problem for workers - not much for general public Uranium Mills – Ore ground to sand – Acid/alkaline leach – Concentrated by ion exchange / solvent extraction 26

Transportation Radioactive materials are transported from the milling location to the conversion location, then from the conversion location to the enrichment location, then from the enrichment location to the fuel fabrication facility, and finally to the power plant. These materials are transported in special containers by specialized transport companies. People involved in the transport process are trained to respond to emergencies. In the US, Asia, and Western Europe transport is mainly by truck, and in Russia mainly by train. Intercontinental transport is usually by ship, and sometimes by air. Since 1971 there has been over 20, 000 shipments with no incidents and limited operator exposure. 27

Nuclear Fuel Cycle Source: http: //www. sonic. net/~kerry/uranium. html 19 March 2018 28

Consumer products Tobacco 210 Pb and 210 Po Coal//natural gas Th and U in ceramics and glass Airport x rays 19 March 2018 29

Man-made Sources of Radiation Consumer products – Television sets – Fossil fuel: coal, gas Air travel Luminous compounds Building materials Nuclear fuel cycle Above-ground bomb tests 19 March 2018 30

Effective doses received during various types of work Dose in milisieverts ‘Non-coal’ mining 16. 3 milisieverts

The San Salvador accident in February 1989 Three employees at an industrial sterilization plant in Salvador were using a very significant Co-60 source of 600 TBq (more than 15, 000 Ci). They were seriously irradiated due to obsolete plant and their not being aware of the risks. As a result of their position and the time they spent near the source, the whole body exposure doses they received have been estimated at 8 Gy, 4 Gy and 3 Gy, respectively. Vomiting appeared less than two hours after exposure. The three victims were referred to the nearest hospital because they felt very tired and could not stop vomiting. They did not present any other sign of acute exposure. Although they had mentioned their work in a plant using ionizing radiation, they were diagnosed as having food poisoning. Acute irradiation syndrome was only recognized three days later when another patient presented with erythema, skin burns, nausea and vomiting and told them that there had been a technical accident at an irradiation plant.

Paints for luminous watch faces In the 1920 s and 1930 s the clock making industry used radium 226 and 228 in radio-luminescent paint for watches. At this time, the risk from alpha emitting radio-elements was almost unknown. The workers who painted the luminous faces had the bad habit of tapering their brushes with their lips. Every time they did this they ingested several becquerels of radium. The fact that radium and calcium are chemical homologues, resulted in rare bone cancers appearing starting from the 20 s, in the form of carcinoma of the sinus of the face. An epidemiological enquiry demonstrated the link between exposure to radium and the risk of bone cancer in 2, 403 workers, whose ingestion of quantities of radium could be evaluated. 64 were suffering from osteosarcoma whereas 2 cases of this type of cancer would have been expected statistically.