CSER 99-003 Rev. 1 Criticality Mass of Uranium as Compared to Plutonium-Implications for PFP Processing Uranium

Abstract

The purpose of this report is to provide information to be used in the evaluation of the CSER and CPS for equipment and activities involved in thermal stabilization. It is well known that for equal mass, {sup 239}Pu is more reactive than {sup 235}U except at fissile material concentrations of 100 g/L to 1,000 g/L. In this range of concentrations, spheres of highly enriched 94% uranium have a lower critical mass than spheres of {sup 239}Pu. Within these same limits, infinite cylinders of highly enriched uranium ({sup 235}U in {sup 238}U) have a smaller critical diameter than infinite cylinders of {sup 239}Pu. This report determines the fissile concentrations between which {sup 239}Pu is more reactive than uranium ({sup 235}U in {sup 238}U). The information can be used for the revision of CSERs and CPS's to allow processing uranium using limits developed for plutonium.

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