Combined calorimetry/neutron coincidence counting/gamma spectrometry (CANEGA) measurements for plutonium mass and isotopic assay

A combined Calorimetry/Neutron Coincidence Counting/Gamma Spectrometry (CANEGA) assay approach offering the potential for improved nondestructive plutonium assay is described. The combination of the six directly measurable quantities as obtained from the three measurement techniques, namely the thermal power P from calorimetry, the effective mass m240eff of 240Pu from neutron coincidence counting (NCC), and the plutonium isotope ratios 238/239, 240/239 and 241/239 and 241Am/239 from high-resolution gamma spectrometry (HRGS) allow to determine the 242Pu isotope abundance, which otherwise cannot be directly obtained from a HRGS measurement. In this manner the CANEGA measurement approach provides a more complete fingerprint for any plutonium-bearing sample under assay, which in turn helps to improve the overall accuracy of the plutonium mass determination. Pertinent features and performances of the individual and combined measurement techniques are presented and discussed.