Radioxenon isotopes measured at radionuclide stations of the Comprehensive Nuclear-Test-Ban Treaty’s (CTBT) International Monitoring System (IMS) may indicate releases from underground nuclear explosions (UNEs) but are often caused by emissions from nuclear facilities. Characterization of CTBT-relevant nuclear events may use the evolution of isotopic activity ratios over time, which goes from the release of an assumed UNE, thr...