From symposium on noble gases; Las Vegas, Nevada, USA (24 Sep 1973). The Livermore Gas Diagnostics Program employs a number of rare gas isotopes, both stable and radioactive, in its investigations of the phenomenology of underground nuclear detonations. Radioactive gases in a sample are radiochemically purified by elution chromatography, and the separated gases are radioassayed by gamma-ray spectrometry and by internal or thin-window beta proportional counting. Concentrations of the stable gases are determined by mass-spectrometry, following chemical removal of the reactive gases in the sample. The most general application of the noble gases is as device fraction indicators to provide a basis for estimating totals of chimney-gas components. All of the stable rare gases except argon have been used as tracers, as have /sup 127/Xe and /sup 85/Kr. /sup 37/Ar and /sup 85/Kr have proven to be of particular value in the absence of a good tracer material as reference species for studies of chimney-gas chemistry. The rate of mixing of chimney gases and the degree to which the sampled gas truly represents the underground gas mixture can be studied with the aid of the fission- product gases. /sup 222/Ra and He are released to the cavity from the surrounding …