Proportional Counter for Monitoring Low Levels of Krypton-85 and Other Beta- and X-Ray-Emitting Nuclides

The use of the inert radioactive gas Kr-85 for tracer studies, leak detection, etc., will become more widespread as the sensitivity of available detectors increases. A multiwire multiplane proportional counter system for beta detection has been developed with a measured minimum detectable concentration for a 3-minute count of 3 × 10-3 pCi cm-3 of Kr-85 in a semi-infinite cloud. Larger proportional counters operated for counting times of several hours can reduce this limit to below 1 × 10-4 pCi cm-3. These detectors should be useful in monitoring low levels of -the radioactive inert gases and of x-ray emitting nuclides.