[en] Calorimetry provides a method to establish the traceability of the nondestructive assay (NDA) of plutonium utilizing the traceability of calorimetric assay and its relative insensitivity to sample matrix. Efforts at Mound Laboratory to establish the traceability of the calorimetric assay of plutonium are described. Results from the Plutonium Metal Exchange Program and a calibration alternatives experiment are the basis for determining the bias between calorimetric assay and chemical assay. The probable cause of the bias is identified. Current uses of calorimetric assay for NDA measurement control and extension of calorimetry to dynamic calibration of NDA are discussed

[en] Inspectors normally use measurements for material verification and for measurement verification. The results of measurement verification by US DOE inspectors are discussed. Biases in plutonium NDA measurements have been determined using calorimetric assay for a verification measurement. Application of the resulting bias corrections have significantly reduced inventory differences in DOE facilities

[en] The second physical inventory verification (PIV) exercise for IAEA inspectors was conducted at a US MOX fabrication facility (WHC) under the auspices of BNL/ISPO in 1984. The IAEA bulk calorimeter was introduced into this exercise. Completely non-destructive calorimetric assay was performed using gamma-ray isotopic measurements. The calorimetric assay measurements on selected items from several strata were used to generate HLNC calibration curves completely independent of operator's values. Outliers from HLNC measurements were also measured by calorimetric assay to demonstrate an in-field alternative to withdrawing aliquots for chemical assay. This exercise demonstrated that the IAEA now has the capability of applying calorimetric assay for these purposes. 3 refs., 3 figs., 3 tabs

No abstract available

No abstract available

[en] Plutonium chemical assay discrepancies involving PuO₂ and (U, Pu)O₂ powders are often caused by a sampling error due to nonhomogeneity of the plutonium concentration and by absorption of several compounds, such as water and carbon dioxide, which render a sample nonrepresentative of the material from which it was drawn. Two techniques have been developed to address these problems. First, a calorimetric watts/gram (W/g) test on the parent material and each pre-weighed sample provides a precise measure of the plutonium elemental and isotopic homogeneity at the time of sampling. Second, total dissolution of the pre-weighed sample for chemical assay eliminates the effects of changes in the sample subsequent to weighing. The W/g test for homogeneity has been demonstrated to be effective and has several potential applications not explicitly addressed in this paper. For shipper-receiver measurements and for inspection samples, representativeness of the samples is demonstrated prior to submission for analysis. Further, prior demonstration of representativeness can result in fewer samples submitted for analysis. Correction for nonhomogeneity through the W/g test on parent material and pre-weighed samples should be investigated

[en] The half life of ²³⁹Pu was measured by member laboratories of the U.S. Half-Life Evaluation committee. Eight separate determinations were made using three different measurement techniques (calorimetry, mass spectrometry and alpha-particle counting). From these measurements, the committee recommends a value of 24,119 + - 26 yr for the half life of ²³⁹Pu. (author)

No abstract available

[en] A joint US/Euratom/IAEA evaluation of the calorimetric assay of large mass, high burn-up PuO₂ was conducted at CEN/SCK, Mol, Belgium, under the USDOE/Euratom agreement fr cooperation in safeguards R and D. Mound provided a large, twin-bridge calorimeter for this demonstration. PuO₂ material from COGEMA-France (Pu-239 approx. = 58 wt %) was prepared by Belgonucleaire. The demonstration was conducted in two phases. The first phase was to evaluate the homogeneity of two batches of PuO₂ which had been blended and characterized at Belgonucleaire in 1980. Watts/gram tests were made on twelve approximately 70g samples from each batch. For the batch selected, the watts/gram test showed an RSD of 0.25%, in good agreement with an RSD of 0.21% in chemical assay values obtained in 1980. Thus, suitable Pu elemental homogeneity with little or no isotopic nonhomogeneity was demonstrated. For the second phase, PuO₂ from the selected batch was packaged into four containers with the PuO₂ content varying from approximately 1 kg to 3 kg; the thermal powers of the four samples varied from 14.5 to 35.8 W. The accuracy of the calorimetric assay of the Pu content of these four containers, compared to chemistry, was 0.3% with measurement times ranging from 4 to 8 hr. These well characterized samples are being used by Euratom and the IAEA for additional NDA evaluation. 4 references, 5 tables

[en] Sampling is a significant source of error in the chemical assay of plutonium. A calorimetric watts/gram of sample (W/g) test on pre-weighed plutonium material is used routinely at Mound to demonstrate material homogeneity, hence, sample representativeness. A prior demonstration of sample representativeness can result in fewer samples submitted for chemical analysis. Combining the W/g test with total dissolution of pre-weighed samples results in accurate plutonium assay. The strategy for applying the W/g test to nonhomogeneous materials needs to be further investigated. 4 tables