Anthropogenic nuclides

Classical speciation of radionuclides is described in Chapter 13. Methodology for single and sequential extraction of soil to assess radionuclide availability to plants is similar to that used for heavy metals, and has recently been reviewed (Kennedy et al., 1997). Therefore, only recent applications of sequential extraction to speci-ate both natural and anthropogenic nuclides are discussed below. 

Anthropogenic nuclides mainly Cs, from nuclear weapon and Chernobyl fall-out, and °Co from steel manufacture. In particular circumstances, there could be other fission product nuclides. 

Cochran JK, Bacon MP, Krishnaswami S, Turekian KK (1983) °Po and °Pb distributions in the central and eastern Indian Ocean. Earth Planet Sci Lett 65 433-445 Cochran JK, Livingston HD, Hirschberg DJ, Surprenant LD (1987) Natural and anthropogenic radionuclide distributions in the northwest Atlantic-ocean. Earth Planet Sci Lett 84 135-152 Cochran JK (1992) The oceanic chemistiy of the uranium and thorium-series nuclides In Uranium-series disequihbrium applications to earth, marine, and environmental sciences. Ivanovich M, Harmon RS (eds) Oxford University Press, New York, p 334-395... 

The third principal component of environmental radioactivity is that due to the activities of humans, the anthropogenic radionuclides. This group of nuclides includes the previously discussed cases of 3H and 14C along with the fission products and the transuranium elements. The primary sources of these nuclides are nuclear weapons tests and nuclear power plant accidents. These events and the gross nuclide releases associated with them are shown in Table 3.1. Except for 14C and... 

There are essentially three sources of radioactive elements. Primordial nuclides are radioactive elements whose half-lives are comparable to the age of our solar system and were present at the formation of Earth. These nuclides are generally referred to as naturally occurring radioactivity and are derived from the radioactive decay of thorium and uranium. Cosmogenic nuclides are atoms that are constantly being synthesized from the bombardment of planetary surfaces by cosmic particles (primarily protons ejected from the Sun), and are also considered natural in their origin. The third source of radioactive nuclides is termed anthropogenic and results from human activity in the production of nuclear power, nuclear weapons, or through the use of particle accelerators. 

Several cosmogenic tracers also qualify as transient tracers at the present time, because of an appreciable contribution from anthropogenic sources (Table 3). Thus, the nuclides H, (produced in appreciable amounts in nuclear weapons testing), tritugenic He and I (which has also been produced in large amounts by nuclear weapons tests and operation of nuclear power plants), serve as (useful) transient tracers in some geophysical reservoirs. 

The ° T1, in the Th decay series, and 7 " Bi in the decay series are used as indicators of the amount of their parents in the materials. Other members of each chain will also be present. Apart from these primordial nuclides (those surviving from the formation of the solar system), traces of anthropogenic (human-made) species are seen, such as Co in steels and Cs in molecular sieves. There are obvious reasons for some of these radioactive contents aluminium always has traces of uranium and thorium within it, and it is not unreasonable to expect in molecular sieves. However, relatively large amounts (compared to other materials in the list) of uranium and thorium daughter nuclides in epoxies and printed circuit boards are unexpected. Clearly, for some materials, there is ample scope for reducing the activity the detector sees by selecting a material with a lower activity. In a similar table to that above, Dassie (in a private communication) reported 4.3 Bq of Cs kg of Csl and 33 Bq of kg of Nal, considerably more than in Table 13.6 this latter would be a problem were it to be used for low level Compton suppression systems. 

NORM Naturally Occurring Radioactive Material. NORM includes some of the primordial nuclides and their daughters and certain nuclides continuously created in the environment. Contrast anthropogenic radiotmclides. 

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