ESTIMATION OF AVERAGE BURNUP OF DAMAGED FUELS LOADED IN FUKUSHIMA DAI-ICHI REACTORS BY USING THE ~(134)Cs/~(137)Cs RATIO METHOD

摘要

Average burnup of damaged fuels loaded in Fukushima Dai-ichi reactors is estimated, using the ~(134)Cs/~(137)Cs ratio method for measured radioactivities of ~(134)Cs/~(137)Cs in contaminated soils within the range of 100 km from the Fukushima Dai-ichi nuclear power plants. As a result, the measured ~(134)Cs/~(137)Cs ratio from the contaminated soil is 0.996±0.07 as of March 11th, 2011. Based on the ~(134)Cs/~(137)Cs ratio method, the estimated burnup of damaged fuels is approximately 17.2±1.5 [GWd/tHM]. It is noted that the numerical results of various calculation codes (SRAC2006/PIJ, SCALE6.0/TRITON, and MVP-BURN) are almost the same evaluation values of ~(134)Cs/~(137)Cs ratio with same evaluated nuclear data library (ENDF-B/VII.O). The void fraction effect in depletion calculation has a major impact on ~(134)Cs/~(137)Cs ratio compared with the differences between JENDL-4.0 and ENDF-B/VII.O.