Relationship Between Reported, As-Packaged Moisture, and Moisture Measurements Made During Surveillance of 3013 Containers

Criteria for stabilizing plutonium-bearing materials, detailed inDOE-STD-3013-2004,1 require verification that moisture contentis less than 0.5 wt. percent at the time of packaging. Thisvalue limits the potential for H2 gas generation from moisturedecomposition to levels that are within the design pressure ofthe 3013 storage container. Ongoing container surveillance andshelf-life studies have confirmed that plutonium oxide containingsalt impurities and moisture can generate H2 gas inside sealedcontainers. The observed levels of H2 inside containers storedfor five years have not approached the limiting case of completeconversion of measured moisture to H2 gas. To understand theseobservations, the reliability of the reported moisture content isone factor that must be considered. The moisture measuring protocolswere inherently biased toward reporting higher than actualmoisture content. This was recognized at the time the protocolswere selected but was seen as desirable for assuring that reportedvalues were conservative in assuring that packaging criteria weremet. Other error sources such as those due to differences in thehandling of the moisture analysis sample after removal from theparent batch can also be presumed to bias towards over-estimatingthe actual moisture content because the greater surface exposureand the relatively smaller ratio of sample mass to moisturein the glovebox atmosphere. Ongoing surveillance of containersin storage at Savannah River Site includes opening multiple containersper year and measuring the moisture on the containedmaterial. In this paper we compare these surveillance data withthe reported moisture on the materials in the same containersat the time of packaging. This comparison is used to better understandthe errors and biases in both the pre-packaging and thesurveillance data.