The Non-Proliferation Experiment (NPE) involved detonating 1 kiloton of chemical explosive in a ?subsurface cavity that also contained bottles of tracer gases. That experiment provided an improved understanding of transport processes relevant to the detection of noble gas signals at the surface that might emanate from a clandestine underground nuclear explosion (UNE). As an alternative to performing large chemical detonations to simulate gas transport from UNEs, we have developed a test bed for gas transport, release and detection studies using a former UNE cavity. The test bed site allows for the opportunity to evaluate pathways to the surface created by the UNE as well as possible gas transport mechanisms including barometric pumping and cavity pressurization. With the test bed we have monitored long-term chemical tracers as well as newly injected tracers. In order to perform high temporal resolution tracer gas monitoring at the test bed site, we have also developed a Subsurface Gas Smart Sampler (SGSS), which has potential application during an actual On Site Inspection (OSI) and will be deployed in OSI field exercises planned for 2014. With gas transport characteristics inferred from these experiments we have also performed a variety of computer simulations that provide an improved understanding of how Xenon isotopic ratios, potentially relevant to determining the source of a radioxenon signal detected at the site of an OSI, may be affected by transport in the subsurface.

Subsurface gas-phase transport and detection of noble gas signals from underground nuclear explosions

248th National Meeting (2014)

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