Particulars of Uranium-Plutonium Nitride Fuel Swelling During Low-Temperature Irradiation in Fast Reactor to Burnup 5.5% h.a

Electron-microscopic and electron-probe x-ray spectral studies of nitride fuel microstructure in thin sections and fractures of pellets in correlation with the xenon distribution were conducted in order to obtain data on the particulars of porosity formation and mechanisms of swelling of nitride fuel during low-temperature irradiation. The results attest indications of restructuring of nitride fuel irradiated to burn up 5.5% h.a. at temperature below 880°C. The formation of some grain structure in the restructuring process, accompanied by emission of gaseous fission products from the fuel matrix into pores, affects the swelling rate of uranium-plutonium nitride fuel.