New capabilities of the PAT plutonium analysis program

The Plutonium Attribute Test (PAT) is a software program originally developed for determining the category of a plutonium sample. The premise for its development was that, to assign Pu samples to particular categories, it is not necessary to determine the abundance of all its isotopes. Rather, it is sufficient to determine only 239 Pu abundance, which is universally used to establish a category assignment, i.e., >90 wt% 239 Pu is low burnup (LBPu), <70 wt% is high burnup (HBPu), and the abundances in between could be considered medium burnup (MBPu) plutonium grade. In contrast to previous Pu isotopic analysis programs which analyse spectra taken with HPGe detectors, the algorithms developed in PAT analyses use spectra taken with medium resolution detectors such as LaBr3(Ce) and CZT detectors. As demonstrated by initial tests, PAT was found capable of not only assigning the material category, but also accurately determining 239 Pu abundance, with several per cent typical relative combined standard uncertainty. Furthermore, an advanced algorithm (A-PAT) was added to allow full isotopic characterization of samples. This paper presents further enhancements of the PAT/A-PAT algorithms towards analysis of heavily shielded samples, samples with varied size and age, as well as mixed oxide (MOX) materials.