High burn-up fuel: Fuel cycle prolongation, targeting parity MOX vs UOX, Th-Pu oxide fuel, applicability to other systems

Efficient use of nuclear fuel for sustainability of nuclear energy can be attained by increase in fuel burnup (>70GWd/t). Existing experimental irradiations of lead fuel assemblies in test and commercial reactors show that targeting equivalent parity MOX vs UOX can be confirmed.Burnup extension of UOx significantly beyond ≈ 60 GWd/t may not be envisaged due to safety concerns about fuel fragmentation, dispersal under off-normal conditions. Commercial use of MOX in LWR has reached about 60 GWd/t, goal would be to go beyond that value. However, economically burnup extension beyond ≈ 60 GWd/t may not be justified. Nevertheless, there is certain interest in prolongation of the fuel cycle duration that would mean a longer fuel stay in a core. It might be that use of UOX with enrichment higher than 5 % and MOX with higher initial content of plutonium will be also required.Thoria-based fuel with elevated content of fissile plutonia potentially provides the option to be longer used in a reactor core due to continued production of fissile uranium-233. Thoria-based fuel shows good resistance to burnup-induced degradation effect, possibly less fragmentation during LOCA events compared with the standard UOX or MOX. Rim-effect is less pronounced in the Thoria-based fuel and as a consequence development of high burnup structure is “postponed”. Thoria-plutonia mixed oxide fuel can be considered in two production modes, i.e. as homogeneous and heterogeneous (when Pu-rich islands are embedded in Thoria matrix). Heterogeneous Th-Pu oxide fuel will have some attributes of ATF type fuel compositions.