Evaluation of the impact of geological parameters on subsurface mass transport of Xenon from underground nuclear explosions

Understanding signatures of fission product gases like xenon from underground nuclear explosions (UNE) is of critical importance to global monitoring efforts. Xenon is an ideal signature for its lack of natural abundance in the subsurface, as well its variety of isotopes produced during a nuclear test (^131mXe, ^133mXe, ¹³³Xe, and ¹³⁵Xe). While noble gases have traditionally been considered non-reactive in the environment, it is still subject to advection, diffusion, and various sorption effects in the subsurface. While many studies have been initiated to further characterize UNE signatures of radioxenon and radioargon, to date, they have yet to fully quantify the migration of these gasses in a manner sufficient for large-scale modeling accuracy. This work presents initial efforts to obtain a more complete picture of xenon gas transport properties through geologic materials. Fully-characterized rock cores consisting of a variety of sandstone and limestone samples will be interrogated with tracer gases consisting of Xenon and two of its chemical surrogates SF₆ and CF₄. The effects of varying porosity, overburden pressure, and temperature will be explored in terms of typical UNE test site parameters. Experimental results will be used for benchmarking computational models to provide and enhanced capability to simulate anticipated signatures from potential UNE events.