Conversion-performance characteristics of light-water-moderated lattices as a function of fuel-to-coolant volume ratio (AWBA Development Program)

The report presents a comprehensive evaluation of the conversion performance characteristics of uranium-based and thorium-based fuel systems in an initial cycle (no recycle of fuel) reactor operation. The conversion performance characteristics for a number of fissile/fertile fuel combinations are evaluated as a function of fuel-to-coolant volume ratio and as a function of cycle length (burnup) and power density. The range of values for fuel-to-coolant volume ratio and power density is large enough to include all practical designs currently envisioned. Only light water is considered. The results reported are believed to identify areas within the nuclear design space that offer the most potential for fuel utilization improvement. The conversion performance characteristics are assessed using a point reactor depletion model. The point solution is based on accurate nuclear modeling techniques, and the nuclear data used in the calculations have extensive experimental qualification. The U-233 O2/Th-232 O2 fuel tends to be superior to all other fuels in conversion performance. For burnup lengths on the order of 10 MWD/KgM there is a breeding potential in tight lattice designs for both the U-233 O2/Th-232 O2 system and Pu O2/U-238 O2 system. However, only the U-233 O2/Th-232O2 case appears practical in light water moderated concepts at practical power densities