Non-Destructive Assay of Curium Contaminated Transuranic Waste Drums

At the Plutonium Facility at Los Alamos National Laboratory, a series of non-destructive assays were performed on five transuranic waste (TRU) drums containing non-plutonium scrap metal that was potentially contaminated with weapons grade plutonium and trace quantities of curium. Typically, waste drums containing metal matrices are assayed for plutonium content using passive neutron coincidence counting techniques. The presence of trace quantities of Cm-244 prevents this type of analysis because of the strong coincidence signal created by spontaneous fission of Cm-244. To discriminate between the plutonium and curium materials present, an active neutron measurement technique was used. A Cf shuffler designed for measurement of uranium bearing materials was calibrated for plutonium in the active mode. The waste drums were then assayed for plutonium content in the shuffler using the active-mode calibration. The curium contamination levels were estimated from the difference between the active-mode measurement in the shuffler and a passive assay in a neutron coincidence counter. Far field gamma-ray measurements were made to identify additional radioactive contaminants and to corroborate the plutonium measurement results obtained from the active-mode assay. This report describes in detail the measurement process used for characterization of these waste drums. The measurement results and the estimated uncertainty will be presented