Qualification of the Canberra Tomographic Gamma Scanner for the Measurement of Plutonium Waste

We report on the methodology and results of recently completed qualification testing of Canberra’s TomographicGamma Scanner (TGS) carried out at the AREVA NC fuel reprocessing facility at La Hague, France. This testingwas performed to demonstrate, among other objectives, the suitability of the TGS technique for the assay ofdrummed Plutonium waste, to evaluate the accuracy and precision achievable by the instrument in this application,and to validate the Total Measurement Uncertainty (TMU) evaluation provided by the manufacturer. The measurementcampaign used of a set of ten simulated waste drum configurations filled with highly heterogeneous matricesof manufactured concrete, PVC, and wood “debris” pieces, and containing well-determined reference sources rangingfrom roughly 300 mg to nearly 60 g of total Pu mass. The non-destructive assay of Pu bearing waste by gammaspectroscopy is a challenging measurement problem due both to the complexity of the spectra and to the compoundingdifficulty of self-absorption effects. The source and matrix configurations in this campaign were furthermoredesigned to present challenging cases deliberately unfavorable to the TGS methodology in order to test the limits ofthe systems performance. The results of this study demonstrate that the TGS, properly calibrated subject to the correctanalysis methods, performs within the expected precision and bias limits of the instrument and that, even underunfavorable conditions, is consistent with the 95% confidence limit of the TMU estimate.