{"id":15902,"date":"2024-05-21T14:01:45","date_gmt":"2024-05-21T13:01:45","guid":{"rendered":"https:\/\/besafenet.net\/naturgefahren\/radiological-emergencies\/"},"modified":"2024-05-21T14:01:46","modified_gmt":"2024-05-21T13:01:46","slug":"radiological-emergencies","status":"publish","type":"page","link":"https:\/\/besafenet.net\/de\/naturgefahren\/radiological-emergencies\/","title":{"rendered":"Radiological Emergencies"},"content":{"rendered":"\t\t
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Technologische Gefahren<\/h2>\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t
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Radiological Emergencies<\/h1>\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/div>\n\t\t\t\t
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Prepared by TESEC – European Centre of Technological Safety (Kiev, Ukraine)<\/em><\/h6>\n\t\t\t\t\t<\/div>\n\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t
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The nuclear accident at the Chernobyl reactor in 1986 shocked the world: more than 100,000 people in Belarus, Ukraine and Russia were evacuated from the contaminated area and about 5 million were exposed. In France, Germany, Poland and other European countries, radiation protection measures were implemented. The Fukushima nuclear accident in 2011 proved that every nuclear reactor harbours a nuclear hazard.<\/p>\n

The public perception of the Chernobyl and Fukushima nuclear accidents clearly demonstrated the lack of public information on radiation hazards associated with releases of radionuclides. As both accidents showed, there is only one trustworthy source of information for communities in such an emergency: their own analysis of the information provided, based on personal basic knowledge.\u00a0
Nowadays, more than 50% of electricity is produced in Nuclear Power Plants (NPPs) in some countries, and radioactive materials are used in medicine, industry, transport, the military and other areas of human activity. We are exposed to natural radiation from space and the Earth (from granite, thorium sand) or through eating natural radioactive potassium and inhaling radioactive radon. Radiation exposure is part of our lives. On the other hand, there are risks from nuclear or radiological accidents where people can die as a result of radiation exposure.\u00a0<\/p>\n\t\t\t\t\t<\/div>\n\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t

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\n\t\t\t\t\t\t\t\t\t\t\t\t\t\n\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t<\/i><\/span>\n\t\t\t\t\t\t\t\t<\/i><\/span>\n\t\t\t\t\t\t\t\t\t\t\t\t\t\t<\/span>\n\t\t\t\t\t\t\t\t\t\t\t\t1. What is Radiological Emergency? <\/a>\n\t\t\t\t\t<\/div>\n\t\t\t\t\t

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The term \u201cRadiological Emergency\u201d generally refers to events involving the release of significant levels of radioactivity and the exposure of workers or the general public to radiation as a result of a Nuclear or Radiological Accident. The source of the hazard is ionising radiation \u2013 the flux of alpha, beta or gamma particles, which is basically the result of radioactive decay. When the energy of radiation is absorbed by matter, chemical changes occur at the atomic and molecular levels. The amount of radiation energy absorbed per gram of matter is called the absorbed dose. The damage to the tissue from a high dose of radiation is so extensive that the body does not have time to regenerate new tissue, and so the effect becomes visible with many of the features of thermal burning, but it is usually much deeper and longer lasting. Extremely high levels of acute radiation exposure can result in death within a few hours, days or weeks.<\/span><\/p>\n

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Humans are primarily exposed to natural radiation from the sun, cosmic rays and naturally occurring radioactive elements found in rocks, food and the environment. Radon, which emanates from the ground, is another major source of natural radiation. Cosmic rays from space include energetic protons, electrons, gamma rays and x-rays.<\/span><\/p>\n

The primary radioactive elements found in the Earth\u2019s crust are uranium, thorium and potassium, and their radioactive derivatives. These elements emit alpha and beta particles, or gamma rays. 
The average doses of population exposure due to all nuclear industry and man-made radioactive sources amount to about 1% of doses due to natural radiation, but exposure in the event of a nuclear or radiological accident can be far higher and enough to cause death.<\/span><\/p>\n


Background of Radioactivity. <\/span><\/i><\/b>All materials are composed of atoms. An atom consists of a positively charged nucleus and negatively charged electrons, which enclose it. An atomic nucleus consists of positively charged protons and neutrons, which lack a charge. The charge of the nucleus is equal to the number of protons in the nucleus. <\/span><\/p>\n

 The chemical properties of atoms depend on only the number of electrons, equals number of protons in the nucleus. There are atoms with the same chemical properties, but different numbers of neutrons in the nucleus. Consequently, they have different physical properties. Some of these atoms could be unstable, or radioactive. <\/span><\/p>\n

Radioactivity is the ability of some nuclei to be spontaneously transformed into another nucleus or into the same nucleus with less energy. The extra energy is released by emitting alpha, beta or gamma particles (in special cases neutrons or others particles can be released). <\/span><\/p>\n

 Atoms with the same chemical properties and a different numbers of neutrons in the nucleus are called isotopes or nuclides. The radioactive isotopes are called radionuclides.  For example, there are three main isotopes of hydrogen. The light isotope has a nucleus with only one proton and it is stable, so its atomic mass number is A=1, and its symbol is 1<\/sup>H. Deuterium is another isotope of hydrogen; it has a nucleus, which consists of one proton and one neutron, and it is also stable. Its atomic mass number is A=2, and its symbol is 2<\/sup>H.  But the isotope of hydrogen, which has a nucleus consisting of one proton and two neutrons, is unstable. Its symbol is 3<\/sup>H and its name is tritium. The stable isotope of iodine is 127<\/sup>I; the isotope 131<\/sup>I (or iodine \u2013 131) is radioactive. Both isotopes have the same chemical properties. The chemical elements in the nature are in some cases the mixture of stable and long-lived isotopes, for example normal potassium, which presents in minerals and food, is mixture of stable isotopes 39<\/sup>K and 41<\/sup>K and long-lived radioactive isotope 40<\/sup>K. <\/span><\/p>\n

If an isotope is radioactive, what is a unit of radioactivity? One decay per second is a unit of radioactivity called becquerel (symbol Bq). The old unit curie (Ci) equals 3.7×1010<\/sup> Bq. Different radioactive isotopes (radionuclides) have different rates of decay. The rate of decay is characterized by a half-life, which is the period of time when half of all the radionuclides will decay, transforming to other atoms. Within the half-life, radioactivity reduces two times, after 2 half-live 4 times, after 3 at 8 times, etc. The short-lived radionuclides have a higher radioactivity than the same amounts of long-lived radionuclides. For example, 131<\/sup>I has a half-life of 8.02 days, and cesium-137 (137<\/sup>Cs ) has a half-life of 30.07 years, so 131<\/sup>I has 1370 times higher radioactivity than 137<\/sup>Cs.<\/span><\/p>\n

Nuclear energy <\/span>could be released not only as a result of radioactive decay, but also from a <\/span>nuclear reaction, which occurs when some nuclei interact with others and create <\/span>new nuclei and could generate energy. Our Sun and other stars shine as a result <\/span>of nuclear reactions. All existing nuclear power reactors produce energy by a <\/span>nuclear fission chain reaction, which, unfortunately, produces very high <\/span>radioactive waste \u2013 the main source of radiological hazard.  Theoretically, it is possible to create <\/span>nuclear reactions, which will produce energy without radioactive waste, but for <\/span>now, nobody knows how to do that. This is a good subject for future research.<\/span><\/p>\t\t\t\t\t<\/div>\n\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/div>\n\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/section>\n\t\t\t\t\t\t\t\t\t<\/div>\n\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/p>\n<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t\t\t

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\n\t\t\t\t\t\t\t\t\t\t\t\t\t\n\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t<\/i><\/span>\n\t\t\t\t\t\t\t\t<\/i><\/span>\n\t\t\t\t\t\t\t\t\t\t\t\t\t\t<\/span>\n\t\t\t\t\t\t\t\t\t\t\t\t2. What types of Radiological Emergency are there?<\/a>\n\t\t\t\t\t<\/div>\n\t\t\t\t\t

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A Nuclear Accident is one involving a device using a controlled nuclear chain reaction for some purpose. For example, a Nuclear Reactor has nuclear fuel which, through a self-sustaining and controlled nuclear chain reaction, produces heat, turning turbines and producing electricity. Because of the energy involved in this process, there is potential for considerable radioactive material to be released and dispersed into the environment. Such a release would be due to a \u201cnuclear accident\u201d and results in a Radiological Emergency. Normally, nuclear accidents with releases into the environment are very rare but they have the potential to lead to widespread dispersion of radioactive material. <\/span>
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A Radiological accident is initiated by lost radiation sources, accidents during transportation of radioactive sources or materials, equipment or human errors in the operation of radiation sources. It could result in a Radiological Emergency if there is a risk of human exposure. Sources, often called \u201csealed sources\u201d, are usually small metal containers in which a small amount of radioactive material is sealed. <\/span><\/p>\n

<\/a><\/a>Nuclear reactors and radiological accidents. <\/span><\/i><\/b>Nuclear reactors are the highest source of radiation and the highest source of radiological risk.<\/span> As of today, the main way for nuclear energy production is a nuclear fission chain reaction.  Heavy nuclei like uranium-235 (235<\/sup>U) splits into two more light nuclei and a few neutrons. Nuclear energy excesses finally transfer to heat energy and then to electricity. The main problem is safety. Nuclei produced in fission are radioactive.<\/span><\/p>\t\t\t\t\t<\/div>\n\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/div>\n\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/section>\n\t\t\t\t

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Fig.2.1 Nuclear fission<\/figcaption>\n\t\t\t\t\t\t\t\t\t\t<\/figure>\n\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/div>\n\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/section>\n\t\t\t\t
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\n \n \n<\/v:path><\/v:stroke><\/v:shapetype>\n \n \n <\/v:textbox><\/v:shape><\/p>

\n \n \n<\/w:wrap>Nowadays about 10% of all electricity in the world <\/span>is <\/span>produced<\/span> in<\/span> <\/span>this<\/span>\nway. There <\/span>is about 300,000 tons of high radioactive spent fuel<\/span> in\nstorage. <\/span>The amount<\/span> of spent fuel <\/span>rises<\/span>\nabout 12,000 ton<\/span>s annually.<\/span><\/o:p><\/span><\/p>

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\n \n \n \n \n \n \n \n \n \n \n \n \n \n \n <\/v:f><\/v:f><\/v:f><\/v:f><\/v:f><\/v:f><\/v:f><\/v:f><\/v:f><\/v:f><\/v:f><\/v:f><\/v:formulas>\n \n \n<\/o:lock><\/v:path><\/v:stroke><\/v:shapetype>\n \n \n \n<\/w:wrap><\/o:lock><\/v:imagedata><\/v:shape>In a nuclear power plant, the heat source is the reactor core. A heat\nsource provides heat to generate steam. A turbine generator uses the energy of\nthe steam to turn a turbine that generates electricity. The pump provides the\nforce to circulate the water through the reactor and other system. <\/o:p><\/span><\/p>

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The nuclear\nfuel typically used is in the form of uranium dioxide (UO2<\/sub>). The\nuranium dioxide is fabricated into cylindrical fuel pellets. These pellets are\nstacked end-to-end to form a fuel rod that is encased in fuel cladding. <\/o:p><\/span><\/p>\t\t\t\t\t<\/div>\n\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/div>\n\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/section>\n\t\t\t\t

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Fig.2.2 The nuclear fuel<\/figcaption>\n\t\t\t\t\t\t\t\t\t\t<\/figure>\n\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/div>\n\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/section>\n\t\t\t\t
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\u00a0<\/p>

Each reactor contains a huge amount of radionuclides. If they were distributed to everyone in the World, people would have significant exposure. The main activity in reactors is from fission products, which have different chemical properties \u2013 gases like xenon-133 (133<\/sup>Xe), volatile elements like iodine-131 (131<\/sup>I) or cesium-137 (137<\/sup>Cs), or solid materials like strontium- 90 (90<\/sup>Sr) or isotopes of plutonium. The main problem for the safe reactor operation is blocking possible release of radionuclides into the environment.\u00a0 Four barriers prevent the release of radioactive fission products from the reactor core to the environment: fuel pellets, fuel cladding, the reactor vessel, and the containment building. Fuel rods trap 99% of all fission products in the fuel pellets and the remaining 1% in the fuel cladding. If the core is not sufficiently covered with water to provide cooling, it could overheat and cause a breakdown in the fuel cladding, and then a fuel meltdown. Even if the fuel cladding were to fail, two more restraints prevent a release to the atmosphere. The reactor core is located within a reactor vessel<\/span> (for main types of reactors), that has walls of steel about 30 centimeters thick. The containment building is the last barrier between the radioactive products and the environment (not all types of reactors have a containment building and they have less safety barriers). It is made of high-density, reinforced concrete as much as two meters thick. The containment building is built to withstand severe accidents and natural and technological hazards (like aircraft crash). Even if the first three barriers are damaged, the containment building should prevent any significant release of fission products to the environment.<\/span><\/p>

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The average dose of exposure due to all nuclear industry and man-made radioactive sources is about 1% from doses due to natural radiation, but it is not the case of nuclear or radiological accident. <\/span><\/p>

Nuclear or Radiological Accident generally refers to events involving the release of a significant amount of radioactivity from reactor (facility), the exposure of workers and\/or the general public to radiation. <\/span><\/p>

Radiological accidents are initiated by the lost radiation sources, accidents during transportation of radioactive sources or materials, equipment or human errors in radiation sources operation. Sources, often called „sealed sources,“ are usually small metal containers in which a small amount of a radioactive material is sealed. Lost source accidents are ones in which a radioactive source is lost, stolen or abandoned. A people finding these sources and not knowing what they are, keep them or even open them and suffer serious exposures. <\/span><\/p>

The nuclear reactors are the most powerful sources of radiation and nuclear accident. If barriers preventing radioactivity release from the reactor core are damaged, first radioactive gases and volatile 131<\/sup>I or 137<\/sup>Cs will be released to the environment. One of the most severe types of accident is a core melt accident. A core melt accident occurs when the heat generated by a nuclear reactor exceeds the heat removed by the cooling systems to the point where at least one nuclear fuel rod exceeds its melting point. A core melt accident can occur even after a reactor is shut down because the fuel continues to produce heat from radionuclides decay. When a nuclear reactor has been shut down and chain nuclear fission is not occurring, a very high source of heat production will still exist due to the radioactive decay of fission fragments. At the moment of reactor shutdown, decay heat will be about 6.5% of the total core power if the reactor has had a long and steady power history. About 1 hour after shutdown, the decay heat will be about 1.5% of the previous core power. After a day, the decay heat falls to 0.4%, and after a week it will be only 0.2%. The decay heat production rate will continue to slowly decrease over time; the decay curve depends upon the proportions of the various fission products in the core and upon their respective half-lives. <\/span><\/p>

The heating of fuel pellets can result in some of the fission products being lost from the pellet. If the radioactive xenon and iodine rapidly leave the pellet, the amount of 134<\/sup>Cs and 137<\/sup>Cs, which is present in the gap between the cladding and the fuel, will increase. If the zircaloy tubes holding the pellets are broken, a greater release of radioactive gases, iodine and cesium from the fuel will occur.<\/span><\/p>

The potential danger from an accident at a nuclear reactor is from exposure to radiation. This exposure could come from the release of radioactive material from the reactor into the atmosphere, usually characterized by a plume (cloud-like) formation. The size of the affected area is determined by the amount and properties of radioactive material released from the reactor, wind direction and speed, and weather conditions (such as rain or snow), which would quickly drive the radioactive material to the ground, causing increased deposition of the radionuclides. Significant contamination could affect areas up to 30 kilometers from the accident site.<\/span><\/p>

The radiation dose received by the public during the first days of a nuclear reactor accident comes mostly from five sources:<\/span><\/p>

1) external gamma radiation from the radioactive cloud or plume, called cloud shine;<\/span><\/p>

2) external gamma radiation from radioactive material deposited on the ground, called ground shine;<\/span><\/p>

3) external beta and gamma radiation from radioactive material deposited on the skin and clothes, buildings and trees;<\/span><\/p>

4) internal exposure from inhaling radioactive material in the plume; and<\/span><\/p>

5) internal exposure from eating and drinking contaminated water and food.<\/span><\/p>

During a release, the exposure dose from cloud shine, ground shine, skin<\/span> and clothing contamination and inhalation of<\/span> radioactive material are the most dangerous.\u00a0 After the plume has passed, the dose from ground shine and eating of contaminated food and milk become most dangerous. Doses from external exposure and inhalation<\/span> can be prevented or reduced by what are referred to as urgent protective measures.\u00a0 These are protective measures that must be implemented urgently or immediately and include sheltering, evacuation, and thyroid blocking. Doses from ingestion can be reduced by restricting immediate consumption of locally produced food.\u00a0\u00a0<\/span><\/p>\t\t\t\t\t<\/div>\n\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/div>\n\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/section>\n\t\t\t\t\t\t\t\t\t<\/div>\n\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/p>\n<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t\t\t

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\n\t\t\t\t\t\t\t\t\t\t\t\t\t\n\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t<\/i><\/span>\n\t\t\t\t\t\t\t\t<\/i><\/span>\n\t\t\t\t\t\t\t\t\t\t\t\t\t\t<\/span>\n\t\t\t\t\t\t\t\t\t\t\t\t3. Why does Nuclear or Radiological Accident occur?<\/a>\n\t\t\t\t\t<\/div>\n\t\t\t\t\t

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Nuclear reactors (used for power generation, military or research purposes) are the main sources of radiation. The radioactivity of a nuclear reactor core is millions of times higher than any other man-made source of radiation. Although the construction and operation of nuclear power plants are closely monitored and regulated, an accident, though unlikely, is possible.\u00a0
The potential danger from an accident at a nuclear reactor is exposure to radiation. This exposure could come from the release of radioactive material from the reactor into the environment, usually characterised by a plume (cloud-like) formation. The size of the area affected is determined by the amount of radioactive material released from the plant, wind direction and speed, and weather conditions (eg rain, snow) which would quickly drive the radioactive material to the ground, causing increased deposition of radionuclides. Significant contamination could affect areas up to 30 kilometres from the accident site.\u00a0

Radiological accidents can occur wherever radioactive materials are used, stored or transported. In addition to nuclear power plants, hospitals, universities, research laboratories, industries, major highways, railways and shipping yards could be the site of a radiological accident. Radioactive sources are frequently used in industrial gauges (eg moisture and density gauges). If these gauges or other radiation-containing equipment are disposed of incorrectly or sent for recycling as scrap metal, the sealed source may be „lost“ and people may be exposed as a result. They are among the most frequently reported radioactive contaminants in shipments received by scrap metal facilities. If a steel mill melts a source, it contaminates the entire batch of metal, the processing equipment and the facility. More importantly, it can result in the exposure of workers or users to radiation.

There have also been incidents in which unsuspecting individuals find these sources and, not knowing what they are, keep them or even open them and suffer serious exposure. Some satellites use radioactive materials as a power source during long space flights. During the launch or re-entry of satellites there is potential for an accident that would disperse radioactive materials.\u00a0<\/p>\t\t\t\t\t<\/div>\n\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/div>\n\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/section>\n\t\t\t\t\t\t\t\t\t<\/div>\n\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/p>\n<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t\t\t

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\n\t\t\t\t\t\t\t\t\t\t\t\t\t\n\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t<\/i><\/span>\n\t\t\t\t\t\t\t\t<\/i><\/span>\n\t\t\t\t\t\t\t\t\t\t\t\t\t\t<\/span>\n\t\t\t\t\t\t\t\t\t\t\t\t4. Where does Nuclear or Radiological Accident occur?<\/a>\n\t\t\t\t\t<\/div>\n\t\t\t\t\t

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Radiation is used in medicine, the military and industry.

The main users of man-made radiation include:<\/p>