Deposition of Plutonium in Tokyo through the End of 1966

Abstract

Integrated amounts of ²³⁹Pu during the period from March 1958to the end of 1966 and ²³⁸Pu (from 1959 to 1966) in Tokyo are respectively 0.92 mCi/km2 and 34 uCi/km².²³⁸Pu to ²³⁹Pu ratio from 1959to 1966 is 3.9% which is nearly the same as that in fallout prior to the satellite failure. The mean ratio of ²³⁹Pu/⁹⁰Sr deposition is 1.6%. Assuming 1.6% activity ratio of ²³⁹Pu/⁹⁰Sr, the total release of ²³9Pu and ²³⁸Pu associated with the nuclear test is estimated to be about 0.22 MCi and <10 kCi respectively in this period.
The mean residence time of 239PU is 1.7 years i n both periods from 1959 to 1961 and from 1963 to 1966, which is slightly longer than that of ⁹⁰Sr (1.4 yr.,1963 to 1966).