Use of Compton suppression gamma ray spectrometry to determine 239 Pu.

Pu has been characterized by gamma-ray spectroscopy for a level higher than the usual environmental ones typically needing alpha spectrometry, ICP-MS or TIMS. The higher activities typically have applications in reprocessing, safeguards verification, and nuclear forensics. For activities of hundreds of Bq/g, it is possible to use gamma ray spectrometry for Pu characterization. A soil reference standard of 185 Bq/g (75 ng/g) was measured on a 79% efficient HPGe with a digital Compton suppression system. The ratios of the counting statistics for suppressed and unsuppressed uncertainties for various Pu photopeaks were determined. The effects of self-attenuation on the low energy gamma rays were evaluated, and it was determined that Compton suppression was an effective characterization method of Pu after accounting for self-attenuation.