Finely Divided Metal as Nuclear Reactor Fuel

Abstract

A new form for metallic nuclear reactor fuel is proposed consisting of finely divided particles (tens of micrometers) mixed with sodium for thermal bond. Fuel pins filled with this form of fuel would have greater fuel density than with solid slugs fabricated at 75% smear density. Greater fuel density reduces enrichment requirements for initial fuel loading. A larger surface-to-volume ratio allows more fission product gases and metallic fission products to diffuse out of fuel particles, resulting in less swelling, greater burnup before processing, and simple preliminary thermomechanical spent fuel processing steps that might be used several times before the more expensive pyroelectric process develolped for the Experimental Breeder Reactor II (EBR-II). Less frequent pyroelectric processing, simple preliminary processing, and a larger surface-to-volume ratio reduce total processing cost. Preliminary processing produces separate fission products, in particular cesium and strontium, in metallic rather than salt or mineral form, thereby simplifying and reducing storage cost. Intrinsically structurally weak fuel would not rupture fuel pin cladding by swelling. The expense and complexity of the process would be offset by reduced total system cost.