Analysis of cesium isotope compositions in environmental samples by thermal ionization mass spectrometry-3

Cesium was recovered from soil samples obtained in Fukushima prefecture. Isotopic analysis of Cs was performed by -spectrometry to determine the activity ratio of Cs-134/Cs-137 and thermal ionization mass spectrometry was used to determine the isotopic ratios of Cs-133/Cs-137 and Cs-135/Cs-137. The analytical results showed that both the activity ratio of Cs-134/Cs-137 and the isotopic ratio of Cs-135/Cs-137 were within the expected values for the Fukushima Daiichi Nuclear Power Plant estimated using the ORIGEN-II code, suggesting that most of the radioactive Cs in the soil sample originated from the Fukushima Daiichi Nuclear Power Plant. The concentration of Cs-137 and the contribution of radioactive Cs from global fallout were correlated to the distance from the Fukushima Daiichi Nuclear Power Plant, while the contribution of radioactive Cs from each reactor did not show any similar distance dependence.