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

摘要

Criteria for stabilizing plutonium-bearing materials, detailed in DOE-STD-3013-2004, require verification that moisture content is less than 0.5 wt. percent at the time of packaging. This value limits the potential for H_2 gas generation from moisture decomposition to levels that are within the design pressure of the 3013 storage container. Ongoing container surveillance and shelf-life studies have confirmed that plutonium oxide containing salt impurities and moisture can generate H_2 gas inside sealed containers. The observed levels of H_2 inside containers stored for five years have not approached the limiting case of complete conversion of measured moisture to H_2 gas. To understand these observations, the reliability of the reported moisture content is one factor that must be considered. The moisture measuring protocols were inherendy biased toward reporting higher than actual moisture content. This was recognized at the time the protocols were selected but was seen as desirable for assuring that reported values were conservative in assuring that packaging criteria were met. Other error sources such as those due to differences in the handling of the moisture analysis sample after removal from the parent batch can also be presumed to bias towards over-estimating the actual moisture content because the greater surface exposure and the relatively smaller ratio of sample mass to moisture in the glovebox atmosphere. Ongoing surveillance of containers in storage at Savannah River Site includes opening multiple containers per year and measuring the moisture on the contained material. In this paper we compare these surveillance data with the reported moisture on the materials in the same containers at the time of packaging. This comparison is used to better understand the errors and biases in both the pre-packaging and the surveillance data.