Fission gas production in reactor fuels including the effects of ternary fission

An understanding of gas bubble formation and migration in nuclear fuel and its impacts on fuel and cladding materials requires knowledge of the isotopic composition of the gases and their generation rates. In this paper, we present results of simulations for the production of the dominant noble gases (helium, xenon, krypton) in nuclear fuels for different reactor core configurations and fuel compositions. The calculations were performed using detailed nuclear burn simulations with Monte Carlo nuclear transport, and included ternary fission to ensure an accurate treatment of helium production. For all reactor designs and fuels considered xenon was found to be the most dominant gas produced. Variation in the composition of fission gases is quantified for: (1) the burn time, (2) the composition of the fuel, and (3) the neutron energy spectrum. These three factors determine the relative fraction of each gas and its transmutation into or from stable gas by subsequent neutron capture.

Research highlights▶ Noble gas productions were simulated in three different nuclear fuels. ▶ Ternary fission was added into CINDER’90 to track ternary fissioned helium. ▶ Xe has by far the largest production, 136Xe decreases with higher fuel enrichment. ▶ Pu based fuel produces less Kr than U based fuel. ▶ Helium produced mainly from transuranic isotopes.