MEU/Th fuel cycle optimization for the Lead Plant

The reference equilibrium cycle fuel composition for the Lead Plant was specified previously by a C/Th ratio of 850 and a fuel rod diameter of 1.17 cm, which is optimal for non-recycle operation and close to optimal for recycle of bred U-233. Subsequent work has emphasized the importance of full recycle of all discharged uranium to maintain the competitive advantage of the MEU/Th cycle. Cycles with full recycle optimize at higher thorium loadings and larger rod diameters. This is an additional benefit for core design and reduces fabrication problems. New optimization studies based on full recycle lead to an equilibrium cycle composition characterized by a C/Th ratio of 600 and a rod diameter of 1.35 cm. The average packing fraction of fuel particles in the rod is 0.43. The C/Th ratio for the initial core is 350, which can also be accommodated with the 1.35 cm rod diameter. Mass flow data for 30 year operation and fuel cycle cost data have been obtained for this cycle and for several other thorium loadings