ORNL-5388 - the Molten Salt Energy Technologies Web Site

4-52
'L 12% 2 02 4 0% %/Th
Denatured U Denatured U Denatured U
Fig. 4.5-1. Mid-Equilibrium Cycle Breeding Ratio Isotopics for
Denatured Oxide-Fueled LMFBRs. (ORNL Cases 7. 8, 9. and 10 from Table 4,5-11
clearly superior. However, it does require a large quantity of fissile plutonium as makeup
since it essentially "transmutes" plutonium into 233U. The
system with the thorium
radial blanket generates significantly less 233U but also markedly reduces the required
plutonium feed. In fact, for the case illustrated, this system actually produces a slight
excess of plutonium. The 233U/Th breeder, characterized by a very small excess 233U production,
does not provide a means for utilizing the plutonium bred in the denatured systems,
and thus it does not appear to have a place in the symbiotic systems utilizing energy-center
reactors paired with dispersed reactors. (The coupling of each type of fissile production
reactor with a particular denatured system is considered in Section 7.2.)
As a final point, preliminary estimates have been made of the safety characteristics
of some of the alternate fuel cycle LMFBRs relative to those of the
reference
cycle. Initial calculations have indicated that the reactivity change due to sodium voiding
of a 233U-fueled system is significantly smaller than that of the corresponding Pu-fueled
system.8 Thus, the denatured reactors, since they are fueled with 233U, would have better
sodium voiding characteristics relative to the reference system. However, for oxide fuels
the reported results indicate that the Doppler coefficient for Tho,-based fuels is comparable
to that of the corresponding 238U02-based fuels.
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