85Kr Extraction from Water Samples

A system for extracting krypton from a sample of natural water preextracted under field conditions is described. A carbon trap at –76°C is used to precipitate inert gases. The β radiation of 85Kr is detected using a 3.5-liter multiwire proportional counter, placed on the ground and in a gallery at a depth of 500 m water equivalent in a low-background counter. The background of the counter enclosed in shielding with a built-in anticoincidence ring in the 85Kr β-particle energy range is 0.8 counts/min on the surface and 2 counts/h in the underground laboratory.