Irradiation performance of nitride fuels

Abstract

The properties and advantages of nitride fuels are well documented in the literature. Basically the high thermal conductivity and uranium density of nitride fuels permit high power density, good breeding ratios, low reactivity swings, and large diameter pins compared to oxides. Nitrides are compatible with cladding alloys and liquid metal coolants, thereby reducing fuel/cladding chemical interactions and permitting the use of sodium-bonded pins and the operation of breached pins. Recent analyses done under similar operating conditions show that - compared to metal - fuels mixed nitrides operate at lower temperatures, produce less cladding strain, have greater margins to failure, result in lower transient temperatures, and have lower sodium void reactivity. Uranium nitride fuel pellet fabrication processes were demonstrated during the SP-100 program, and irradiated nitride fuels can be reprocessed by the PUREX process. Irradiation performance data suggest that nitrides have low fission gas release and swelling rates thereby permitting favorable pin designs and long lifetime. The objective of this report is to summarize the available nitride irradiation performance data base and to recommend optimum nitride characteristics for use in advanced liquid metal reactors.