Decision models for optimizing fuel enrichment services under long-term fixed-commitment contracts

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Virginia Polytechnic Institute and State University

The purpose of this study is to construct and test decision models that will enable utility companies to identify cost effective strategies for dealing with enrichment service contracts. Specifically, three decision models are developed to analyze the 18 month decision points of the Long-Term Fixed-Commitment Contract for ten contracting years.

The first model indicates ERDA's current method for acquiring enrichment services assuming maintenance of the split-tails mode of enrichment plant operation. The second model, referred to as the static decision model, utilizes the variable tails concept at a single 18 month decision point. The third model uses the basic equations of the second model to develop a dynamic inventory system that is designed to manipulate the fuel inventories and tails enrichments at the 18 month decision points over ten years.

The application of the three decision models is done by using data from a typical ten year fuel contract for a 1000 Mwe reactor. A computer code is constructed to solve the decision models for the optimum decision policy in contracting for fuel enrichment services.

The results indicate that the application of the dynamic inventory model produces a significant amount of savings in utility costs and uranium feed. The dynamic inventory process is more economical than the split-tails method because the utility company is allowed to manipulate the tails enrichment and the fuel inventories in the dynamic model. The dynamic inventory model appears to be an appropriate vehicle for improving the fixed-commitment contract and more study is merited.