Influence of natural lithospheric radioxenon background on CTBT-compliant subsurface noble gas samples

The verification regime of the comprehensive nuclear-test-ban treaty (CTBT) requires, among other measures, the sampling of subsurface radioxenon in the vicinity of a suspected underground test site. Mixed with the contingent xenon yield of a nuclear explosion is the natural xenon content of the surrounding minerals. This background is caused by the decay of natural uranium and thorium occurrences. Spontaneous and induced fission have to be taken into account, the assessment of which requires detailed knowledge of the prevalent neutron spectrum generated by fission, alpha particles and cosmic radiation. The influence of the resulting xenon quantities and ratios on subsurface sample analysis can thus be evaluated