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

摘要

We report on the methodology and results of recently completed qualification testing of Canberra's Tomographic Gamma Scanner (TGS) carried out at the AREVA NC fuel reprocessing facility at La Hague, France. This testing was performed to demonstrate, among other objectives, the suitability of the TGS technique for the assay of drummed 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 measurement campaign used of a set of ten simulated waste drum configurations filled with highly heterogeneous matrices of manufactured concrete, PVC, and wood "debris" pieces, and containing well-determined reference sources ranging from roughly 300 mg to nearly 60 g of total Pu mass. The non-destructive assay of Pu bearing waste by gamma spectroscopy is a challenging measurement problem due both to the complexity of the spectra and to the compounding difficulty of self-absorption effects. The source and matrix configurations in this campaign were furthermore designed to present challenging cases deliberately unfavorable to the TGS methodology in order to test the limits of the systems performance. The results of this study demonstrate that the TGS, properly calibrated subject to the correct analysis methods, performs within the expected precision and bias limits of the instrument and that, even under unfavorable conditions, is consistent with the 95% confidence limit of the TMU estimate.