DISPOSAL OF DOE-OWNED SPENT FUEL

The M&O Contractor to the U.S. DOE Office of Civilian Radioactive Waste Management is developing designs of waste packages that will contain not only spent nuclear fuel assemblies from civilian nuclear power plants, but also much of the spent fuel from a variety of government programs. Although this fuel from government programs will represent only a small percentage of the total high level waste in the potential repository, the variety of characteristics of these fuel types makes disposal particularly challenging. There are more than 200 varieties of DOE-owned spent nuclear fuels (SNF) that have been grouped into 9 types for analysis by the National Spent Nuclear Fuel Program. Some of this fuel is highly enriched, and some severely degraded. This paper addresses the types of analyses that will be performed in developing waste package designs for DOE-SNF, highlighting the disposal-criticality risk-based methodology and analyses. However, the effects of other characteristics are also discussed -- combustibility and pyrophoricity, residual water, and the very small particle size in some deteriorated fuels. Examples of the development of designs for specific fuels are presented, as are analyses to verify the design’s acceptability. The limiting condition for criticality analysis of DOE-SNF is usually degraded – that is, the waste package has been breached and water has entered and corroded the structural components exposing the fuel. Evaluating the credible degraded configurations is the most difficult part of criticality control analysis. Although the analysis methodology is essentially the same for both DOE-SNF and commercial spent fuel, the varying characteristics including condition and initial enrichment require special analytical treatments. This paper compares commercial and DOE-SNF, and delineates steps that must be taken to ensure that the packaging of DOE-SNF will meet the requirements of 10.CFR. 60 and be safely placed in a repository.