DEPOSITION FRACTIONS OF FISSION PRODUCT AND HEAVY ELEMENTS ON SOIL IN FUKUSHIMA DAI-ICHI NUCLEAR POWER PLANT ACCIDENT

Based on radioactivity measurement of soil samples in the site of Fukushima Dai-Ichi Nuclear Power Station, radioactivity of Sr, Nb, Mo, Tc, Ru, Ag, Te, I, Cs, Ba, La, Pu, Am, and Cm isotopes were compiled as radioactivity ratios to Cs-137. By exponentially fitting or averaging, the radioactivity ratios at the core shutdown were estimated. They were divided by those of the fuel of the core at the shutdown to obtain a deposited radioactivity fractions of the nuclides as relative values to Cs-137, which also correspond to deposition fractions of the elements as relative values to Cs. They were estimated to be orders of 10(-4) to 10(-3) for Sr, 10(-4) for Nb, 10(-2) to 10(-1) for Mo, 10(-1) for Ag, 10(-1) to 10(0) for Te, 10(0) for I, 10(-3) for Ba, 10(-6) to 10(-6) for Pu, 10(-6) to 10(-6) for Am, and 10(-6) for Cm. The observed radioactivity ratios to Cs-137 were compared with those obtained by severe accident analysis to assess the validation of the analysis.