Effect of Nitride Nuclear Fuel Structure and Phase Composition on Fuel-Rod Life

Abstract

The behavior of mixed uranium-plutonium nitride fuel and uranium nitride was studied by means of thermogravimetry at high temperatures (to 2173 K) in a helium flow. The mass loss of the nitride samples was found in the low temperature range (<1773 K), which is not associated with decomposition of uranium or plutonium mononitrides. The mass loss occurs in two stages and is accompanied by the release of nitrogen. It is shown that nitride fuel can contain up to several percent of uranium sesquinitride U₂N₃, which decomposes in the indicated temperature range and can strongly affect pellet integrity and fuel-rod life during operation.