Plutonium-238 in fallout.
The observed variation in the activity ratio of plutonium-238 to plutonium-239 plus plutonium-240 in rainwater in Japan over the period from 1961 through 1968 seems to indicate that the influence of the plutonium-238 released by the burnup of the nuclear auxiliary power generator (SNAP-9A) became noticeable within about 6 months and that variation in the isotope ratio with time is affected by nuclear debris produced in the latest explosions as well as by the plutonium-238 released from the SNAP-9A generator.
D005107:Explosions; D049673:History, 20th Century; D007564:Japan; D011005:Plutonium / Q000032:analysis*; D011847:Radioactive Fallout; D014867:Water / Q000032:analysis
D011847:Radioactive Fallout; D014867:Water; D011005:Plutonium