Sources of Radioactivity

Two groups of radioactivity sources on the earth are to be distinguished, natural and anthropogenic. Natural sources such as and have been pro- 

By mining of ores and minerals, appreciable amounts of natural radionuclides, in particular K, Th, and the members of the thorium, uranium and 

Radionuclides of major importance in the geosphere and the biosphere are listed in Table 21.1. Not taken into account are radionuclides with half-lives h/2 1 d (in the case of activation products of materials used in nuclear reactors, i/2 1 y) and with half-lives ti/2 lO y, radionuclides with fission yields 0.01%, radioisotopes of elements that are not members of the natural decay series,and radionuclides produced solely for medical or technical applications. The radionuclides are arranged according to their position in the Periodic Table of the elements, in order to facilitate the discussion of their chemical behaviour. Radionuclides with half-lives 10y are underlined, because their behaviour over long periods of time is of special importance. 

and K are also low, whereas they are high for many fission products and for the actinides. 

Element Group of the Periodic Table Radionuclide (halLIife) Source 

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A reactor core s fission product inventory is the primary source of radioactivity from which the public is protected by the following independent barriers ... 

The principal source of radioactivity in the human body is potassium-40. About 35 000 potassium-40 nuclei disintegrated in your body while you were reading this sentence. 

In order to investigate chemical reaction mechanisms, it is useful to know the point at which the reaction starts. Regrettably, this is only rarely possible in Szilard-Chalmers studies, and is the object of one of the two most vigorous arguments in the field whether the bonds are all broken and there is a successive rebuilding of the molecules, or these is only a partial breakage of bonds, and little rebuilding is necessary. To illustrate with < 3 As, two possible sources of radioactive parent molecules are... 

Although much of the preceding discussion involved the synthesis of new molecules by organic and inorganic chemists, there is another area of chemistry in which such creation is important—the synthesis of new atoms. The periodic table lists elements that have been discovered and isolated from nature, but a few have been created by human activity. Collision of atomic particles with the nuclei of existing atoms is the normal source of radioactive isotopes and of some of the very heavy elements at the bottom of the periodic table. Indeed nuclear chemists and physicists have created some of the most important elements that are used for nuclear energy and nuclear weapons, plutonium in particular. 

Data from Joseph, A.B., RF. Gustafson, I.R. Russell, E.A. Schuert, H.L. Volchok, and A. Tamplin. 1971. Sources of radioactivity and their characteristics. Pages 6-41 in National Academy of Sciences. Radioactivity in the Marine Environment. Natl. Acad. Sci., Panel on Radioactivity in the Marine Environment, Washington, D.C. 

Isotope Half-life Source of radioactive isotope... 

The other types of radioactive materials cited in this section (medical industry and food industry sources) produce significantly lower activity levels than fuel from a nuclear power plant. However, these sources of radioactive materials may be appealing to terrorists because they are far more accessible. Thousands of hospitals, medical treatment facilities, and food industry plants scattered across the U.S. are protected by relatively low levels of security. 

Radon s main use is as a short-lived source of radioactivity for medical purposes. It is collected from the decay of radium as a gas and sealed in small glass capsules that are then inserted at the site of the cancer. It is also used to trace leaks in gas and liquid pipelines and to measure their rate of flow. The rate at which radon gas escapes from the Earth is one measurement that helps scientists predict earthquakes. 

Fig. 3. Schematic illustration of the interface of the nuclear fuel cycle with geochemical/hydrological cycles. The geological repository is the interface for these two cycles. The principal sources of radioactivity (over the long term) are indicated by the radionuclides listed at the centre of each cycle. Total background exposures to radiation are less than 300 mrem/y. The total radiation exposure that can be attributed to the nuclear fuel cycle is less than 3 mrem/y.

Procedure. In preparation for a series of experimental runs, the top and bottom sections of the furnace were brought to their proper operating temperatures, the air flow was started, and a standby source of radioactive oxide vapor was inserted into the lower section of the furnace. After about a 24-hour equilibration period, the standby oxide source was replaced with the regular source which had just been weighed. 

There are few medical tests to determine if you have been exposed to radium. There is a urine test to determine if you have been exposed to a source of radioactivity such as radium. There is also a test to measure the amount of radon, a breakdown product of radium, when it is exhaled. These tests require special equipment and cannot be done in a doctor s office. Another test can measure the total amount of radioactivity in the body however, this test is not used except in special cases of high exposure. 

The impact of all the sources of radioactivity in the zone of the Arctic coast on the local population has not been assessed reliably enough. It was particularly difficult to separate the natural and anthropogenic components of such an impact. Aibulatov (2000) discussed future research into Russian Arctic radioactive pollution, including... 

While the actinides Pu, Am, Np and Cm are critically important to assessments of the exposure of humans to environmental sources of radioactivity due to their highly hazardous a emissions, the role which the plant root absorption pathway plays in this exposure is relatively small. A conservative estimate of the degree to which plants will incorporate Pu from soil, for instance, is 10% (ie, a soil-to-plant transfer factor of... 

In the course of TSF rimning shielding barriers of some storage facilities degraded and partly lost their functions. As a result, radionuclides contaminated soils, aquatic systems, buildings and constructions generating thereby secondary sources of radioactive contamination requiring localization and elimination. 

RW stored at SRW TSF are not only a high-active source of external y-radiation, but also a source of radionuclide migrations via ground beyond the pad boundaries and thus a source of potential contamination of marine ecosystems. Comparisons of the results of investigations performed in 1999 [2] and in 2003 [5] revealed an increase in surface of contaminated areas around SRW TSF, not only containers with SFAs but also those with SRW being sources of radioactive contamination. 

Many coastal ecosystems have elevated levels of metals and radionuclides (14). Anthropogenic sources of stable isotopes of metals include sewage disposal plants, electroplating plants, and mining and dredging operations sources of radioactive isotopes include effluents from nuclear power plants and submarines, medical establishments, and uranium ore mining. The pollution from most of these operations results from routine or accidental discharges and are either continuous or episodic. 

Polonium was discovered in 1898 by Marie and Pierre Curie in their search for the sources of radioactivity in pitchblende. Polonium has 27 isotopes and is highly toxic and very radioactive. It has been suggested that the isotope 210Po, a natural contaminant of tobacco and an a-particle producer (see Section 21.1), might be at least partly responsible for the incidence of cancer in smokers. 

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