PNNL

Abstract

A new algorithm (Xcounts) is introduced for estimating the activity concentrations of the xenon isotopes 131mXe, 133mXe, 133Xe, and 135Xe using beta-gamma coincidence data. The algorithm simultaneously estimates the decay counts associated with the four xenon isotopes, background, and radon in contrast to the net-counts method that uses sequential residual removal to account for background and interreferences. Calibration data for background counts are determined from gas-background measurements and simulation. In Xcounts, the false positive count rates for 131mXe and 133mXe are lower than the false positive rates for 133Xe and 135Xe. This algorithm appears to reliably detect the metastable isotopes at lower activity levels than the net-counts method and have similar performance for the other isotopes.