Year
2000
Abstract
In 1977 calorimeter measurements of containers of PuO2/UO2 (mixed oxide, or MOX) powder were made in a demonstration of an Automated Plutonium Assay System (APAS) at the United States Department of Energy Mound Laboratory. Replicate measurements using two water-bath calorimeters were made on six 0.5 L containers of MOX with plutonium contents ranging from 26 to 258 g, three containers with 238Pu heat standards, and one empty container. The mixed oxide was 26% plutonium (17% 240Pu). Using a robotic loader with 24-hour-a-day operation, 1872 thermal power measurements were performed over a 56-day period. The calorimeters were operated in servo mode and the temperature of the items measured was preconditioned. The calorimeter measurement time was one hour per item. The relative precision of the thermal power measurements ranged from 0.4% RSD for the 26-g plutonium item to 0.06% relative standard deviation (RSD) for the 258-g plutonium item. The effective specific power (Peff) of the MOX was calculated using plutonium isotopic information determined by mass spectrometry and alpha counting. The plutonium content of the MOX in each container was determined by Peff and the calorimeter measurement. The Pu content of the MOX material in each can was also determined by coulometry and mass. Biases less than 0.1% were observed between the two measurement sets for samples with plutonium contents greater than about 100 g. This paper describes the calorimeter portion of the APAS and its measurement performance, unpublished until now. The APAS demonstration showed that calorimetry is a suitable technique for accurate measurements of major material flows in a high-throughput, MOX production facility.