A Comparative Study of Tritium Breeding Performance of Lithium, Li₂O, and Li₇Pb₂ Blankets in a Tokamak Power Reactor

A nuclear analysis of tritium breeding performance has been carried out for three candidate breeding materials of liquid lithium, solid Li₂O, and solid Li₇Pb₂. Blanket coolants studied include helium gas, liquid lithium, and water. It is found that the Li₇Pb₂ compound gives slightly higher breeding ratios than liquid lithium and significantly higher rates than does Li₂O. The Li₂O blankets reach their full breeding capability at smaller thicknesses due to moderation of the neutron spectrum by the oxygen. Due to this moderation inherent to the use of Li₂O, the incorporation of a carbon reflector does not improve the performance of the blanket nearly as much as it does the performance of the Li₇Pb₂ and lithium blankets. In all of the cases investigated, it has turned out a thin beryllium zone separating the first wall from the breeding blanket substantially enhances the tritium production. Very little incentive for enriching any of the breeders with ⁶Li is found under conditions both with and without beryllium neutron multiplier. Calculations for water-cooled systems indicate a possible improvement in breeding performance over that obtained with helium, particularly for Li₇Pb₂ systems.