Levels of radionuclides in plant samples collected around the uranium conversion facility following the criticality accident in Tokai-mura.

Abstract Concentrations of artificial radionuclides in plant samples collected in the surrounding areas of the uranium conversion facility of JCO Company Limited were studied following the criticality accident in Tokai-mura. Radionuclides detected in plants were 131 I , 133 I , 140 Ba - 140 La and 137 Cs . The highest concentrations of the nuclides were found in samples collected near the facility or its ventilation exhaust and the concentrations decreased sharply with distance. The origins of 140 Ba - 140 La and 137 Cs were thought to be from 140 Xe and 137 Xe , respectively, which were produced in the fission event and released to the atmosphere. The average 131 I / 133 I activity ratio was about 21 (decay-corrected to the end of fission). Levels of the radionuclides in plants outside the JCO grounds were markedly below the intervention levels for foodstuffs in Japan.