Discharges of ¹⁴C from nuclear facilities. Implication in environmental science

At present as C-14 existing in environment, there are that formed by cosmic ray in nature, by nuclear explosion experiment and released from nuclear facilities. As for the former two, the actual situation has been grasped, but the last one lacks the sure information as the range of its influence is local. In this study, the actual situation was explored based on the numerical evaluation of the amount generated in nuclear facilities and the investigative and analytical data by actual measurement. The rate of formation of natural C-14 is closely related to the variation of cosmic ray intensity and energy spectra. The specific radioactivity is 12.9 - 15.3 dpm/g, and it lowers due to the Suess effect, namely the increase of dead carbon. The C-14 due to nuclear explosion experiment reached the highest level of twice as much as the natural level in 1963, but thereafter, it decreased, and at present, it is 15-20% more than the natural level. The nuclear reaction and the reaction cross section of C-14 formation in LWRs, LMFBRs and HTGRs are shown. The formation of C-14 in fuel, core structures and cooling water of LWRs and in other types of reactors, and the examples of C-14 measurement around nuclear facilities are reported. (K.I.)