PNNL

Abstract

The Comprehensive Nuclear Test-Ban Treaty, which is intended to prevent nuclear weapon testing, includes a verification regime, which provides monitoring to identify potential nuclear testing. The presence of elevated 37Ar is one way to identify subsurface nuclear testing. However, the naturally occurring formation of 37Ar in the subsurface adds a complicating factor. Prediction of the naturally occurring concentration of 37Ar can help to determine if a measured 37Ar concentration is elevated. The naturally occurring 37Ar background concentration has been shown to vary between less than 1 mBq/m3 to greater than 100 mBq/m3 (Riedmann and Purtschert 2011). Here, we evaluate a model for predicting the average concentration of 37Ar at any depth under transient barometric pressures, and compare it with measurements. This model is shown to compare favorably with concentrations of 37Ar measured at multiple locations in the Northwestern United States.