Performance analysis of ~(233)U for fixed bed nuclear reactors

摘要

Criticality and burn up behavior of the Fixed Bed Nuclear Reactor (FBNR) are investigated for the mixed fuel ~(233)UO_2/ThO_2 as an alternative to low enriched ~(235)UO_2 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% ~(233)UO_2 with the mixed ~(233)UO_2/ThO_2 fuel. At higher ~(233)U fractions, reactor criticality rises rapidly and exceeds k_(eff)> 1.5 already by 9% ~(233)UO_2. With 100% ~(233)UO_2, start up criticality can reach k_(eff)f= 2.0975. Time dependent reactor criticality k_(eff) and fuel burn up have been investigated for two different mixed fuel ~(233)UO_2/ ThO_2 compositions, namely: 4 % ~(233)UO_2 + 96 % ThO_2 for a reactor power of 40 MW_(el) (120 MW_(th)) and 9 % ~(233)UO_2 + 91 % ThO_2 for a reactor power of 70 MW_(el) (210 MW_(th)). Sufficient reactor criticality (k_(eff)> 1.06) for continuous operation without fuel change can be sustained during ~ 5 and 12 years with 4 % and 9 % ~(233)UO_2 fractions in the mixed fuel, leading to burn ups of ～36000 and > 105000MWD/t, respectively. Thorium based fuel produces no prolific uranium. Plutonium production remains negligible.