Performance analysis of 233U for fixed bed nuclear reactors

Abstract

Criticality and burn up behavior of the Fixed Bed Nuclear Reactor (FBNR) are investigated for the mixed fuel 233UO2/ThO2 as an alternative to low enriched 235UO2 fuel. CERMET fuel with a zirconium matrix and cladding has been used throughout the study. The main results of the study can be summarized as follows: Reactor criticality is already achieved by ∼2% 233UO2 with the mixed 233UO2/ThO2 fuel. At higher 233U fractions, reactor criticality rises rapidly and exceeds keff > 1.5 already by 9% 233UO2. With 100% 233UO 2, start up criticality can reach keff = 2.0975. Time dependent reactor criticality keff and fuel burn up have been investigated for two different mixed fuel 233UO2/ThO 2 compositions, namely: 4 % 233UO2 + 96 % ThO2 for a reactor power of 40 MWel (120 MWth) and 9 % thUO2 + 91 % ThO2 for a reactor power of 70 MWel (210 MWth). Sufficient reactor criticality (keff > 1.06) for continuous operation without fuel change can be sustained during ∼5 and 12 years with 4 % and 9 % 233UO 2 fractions in the mixed fuel, leading to burn ups of ∼36000 and > 105000 MWD/t, respectively. Thorium based fuel produces no prolific uranium. Plutonium production remains negligible. © Carl Hanser Verlag, München.