FALLOUT PARTICLES OF HIGH SPECIFIC ACTIVITY

Particulate air-borne fall-out was measured on filters exposed in a daily contamination survey in Rio de Janeiro, Brazil. On June 25, 1957, a particle of rather uncommon size ( gamma = 4 mu ) and activity (5 x 10/sup -9/ curie) was caught. By applying Way and Wigner's decay law for fission products, its origin could be traced back to the first British H-bomb test in the Christmas Islands 50 days earlier. Analysis of the absorption curve, reduced to parallel beam incidence by meaas of Gross' transform, and comparison tests with a P/sup 32/ standard led to a separation into 3 main groups of beta emitters present. Their energies identify the various fission products making up the activity of the particle. 0/ deg C was con- Y/sup 90/ consitute its near totality. Particle size, shape, and activity are given; physical implications, as well as possible biological consequences, are mentioned. (auth)