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

Abstract

Cesium was recovered from soil samples obtained in Fukushima prefecture. Isotopic analysis of Cs was performed by γ-spectrometry to determine the activity ratio of 134Cs/137Cs and thermal ionization mass spectrometry was used to determine the isotopic ratios of 133Cs/137Cs and 135Cs/137Cs. The analytical results showed that both the activity ratio of 134Cs/137Cs and the isotopic ratio of 135Cs/137Cs 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 137Cs 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.