The radioactivity of atmospheric krypton in 1949--1950

The chemical element, krypton, whose principal source is the atmosphere, had a long-lived radioactive content, in the mid 1940s, of less than 5 dis. per min. per liter of krypton. In the late 1940s this had risen to values in the range of a hundred dis. per min. per liter. It is now some hundred times higher than the late 1940 values. This radioactivity is the result of the dissolving of nuclear fuel for military and civilian purposes, and the release thereby of the fission product krypton-85 (half-life 10.73 years, fission yield about 0.2%). The present largest emitter of krypton-85 is the French reprocessing plant at Cap-de-la Hague