O. V. Mykhailov1, V. M. Bezmylov1, A. K. Terzi2
1Institute for Safety Problems of Nuclear Power Plants, NAS of Ukraine,
36a, Kirova st., Chornobyl, 07270, Ukraine,
2SSE “Chornobyl NPP”, Slavutych, 07101, Ukraine
Chornobyl NPP’s operational wastes accumulated before 1986 accident in State Specialized Enterprise “Chornobyl Nuclear Power Plant” solid waste repository (SWR) were studied. Material content of SRW at around 1 m depth in “light” eastern compartment was identified. After a visual examination, the waste materials were split into four streams. Representative samples for laboratory analysis were collected from each waste stream. Specific activities of 24 radionuclides to be certi-fied before the waste is disposed at the Plant for solid radwaste treatment, were in vestigated. Parameters of correlation between radionuclide activities in specimens were defined. A statistical correlation can be checked for data set without abnormal results and results on values of radionuclide specific activities being less than minimum detectable activity (MDA). The research results demonstrated that the total radioactivity of SRW in the outer layer of eastern compartment storage is, mainly, determined by the content of such radionuclides as 137Cs, 60Co, 90Sr, 94Nb, 235U, 238U, 241Am, 3H and 14C. The data obtained indicate that the scaling factor method can be applied to quantify the specific activity of difficult-to-measure (DTM) radionuclides in the waste. Specific activity of DTM radionuclides such as 90Sr, 94Nb and 241Am can be evaluated with high enough accuracy with using gamma spectrometry of 137Cs and/or 60Co key nuclides (KN). For the rest DTM radionuclides to be certified in the waste, their content according to gamma-ray spectrometry data of KN can be estimated with using Medium Activity Method technique.
Keywords: Chornobyl NPP, solid radioactive waste, specific activities, difficult-to-measure radionuclides, key nuclides, correlation factor, scaling factor.
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