Reduced Enrichment Fuel and Its Reactivity Effects in the University Training Reactor Moata

摘要

Concern for nuclear proliferation is likely to preclude future supply of highly enriched uranium fuel for research reactors such as the University Training Reactor Moata. This study calculates the fuel densities necessary to maintain the reactivity per plate of the present high enrichment (90 per cent exp 235 U) fuel for a range of lower enrichments assuming that no geometry changes are allowed. The maximum uranium density for commercially available aluminium-type research reactor fuels is generally considered to be about 1.7 g cm exp -3 . With this density limitation, the minimum enrichment to maintain present reactivity per plate is about 35 per cent exp 235 U. For low enrichment (max. 20 per cent exp 235 U) fuel, the required U density is about 2.9 g cm exp -3 , which is beyond the expected range for UAl/sub x/-Al but within that projected for the longer term development and full qualification for U sub 3 O sub 8 -Al. Medium enrichment (nominally 45 per cent exp 235 U) Al/sub x/-Al would be entirely satisfactory as an immediate replacement fuel, requiring no modifications to the reactor and operating procedures, and minimal reappraisal of safety issues. Included in this study are calculations of the fuel coefficients at various enrichments, the effect of replacing standard fuel plates or complete elements with 45 per cent enriched fuel, and the reactivity to be gained by replacing 12-plate with 13-plate elements. (Atomindex citation 15:010309)