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The Nuclear Fuel Cycle |
Division for Radiation Safety and Security, Paul Scherrer Institute, CH-5232 Villigen, Switzerland jost.eikenberg{at}psi.ch
Two sources contribute essentially to the presence of anthropogenic radioisotopes in the environment: (i) release from nuclear materials with a major fraction derived from the nuclear bomb testing period during the period 1950–1963 and (ii) emissions from the nuclear industry, such as waste waters from U-mine tailing or nuclear fuel reprocessing plants. This chapter focuses mainly on the major source responsible for global surface contamination, that is, radioisotope aerosol deposition after release into the atmosphere. The atmospheric emissions were caused mainly via surface atomic bomb tests and reactor accidents, with the Chernobyl reactor catastrophe as the most important contribution. In contrast with most fission products, almost all actinides (which are produced via neutron capture reactions) are rather long lived and can be measured in environmental samples with high precision. Some of the actinides (i.e., U, Pu, Cm) consist of various isotopes (e.g.,238,239,240,241Pu) and hence can be used to distinguish between soil contamination from different emission sources. Approaches are therefore presented for calculating the different fractions of contaminants by use of characteristic isotopic signatures.
