A study on plutonium fallout

Abstract

Total depositions of 239,240Pu and 238Pu from 1958 to April 1969 are, respectively, 0.97 mc/km2 and 42 μc/km2 in Tokyo. The ratio of 238Pu to 239,240Pu increased in fallout remarkably since 1967. This increase is considered to be due to 238Pu scattered from SNAP-9A generator in 1964. Surface values of plutonium isotopes of the Japan Sea ranged from 3.0 to 20.4 × 10−15 g/l (0.2 to 1.2 × 10−3 pc/l) with the ratio of 238Pu to 239,240Pu ranging from 13.2 to 37.7%. We observed the deep penetration of these isotopes in the sea.