Qualifying Nondestructive Assay for Plutonium Accountancy Measurements

Reliable estimates of the precision and accuracy of nondestructive calorimetric assay have been made for a wide variety of plutonium-isotopic compositions and material forms. Material forms studied include oxides, metals, mixed-oxides and intermediate-process categories. Isotopic compositions range from 6 to 22% plutonium-240. Quantities ranged from 0.2 to 2000 g of plutonium. Estimates of accuracy and precision were based on comparison with traditional wet chemical assay techniques. Typically, the precisions and accuracies were 0.5% or better. These error estimates are in good agreement with internal uncertainties propagated from the calorimeter precision and the statistical uncertainties associated with the gamma-ray isotopic measurement. The measurement techniques can thus be applied to a wide variety of materials without performing similar experiments on every material category in the process. An example is also given using this technique to calibrate another plutonium NDA method using the dynamic calibration approach.