ORNL-5388 - the Molten Salt Energy Technologies Web Site

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7.2.4. Conclusions
Since optimization of the various reactors for the particular fuel cycle considered
was beyond the scope of this study, the results presented above are subject to several uncer-
tainties. Nevertheless, certain general conclusions on the impact of the various fuel
cycles on reactor performance are believed to be valid:
For once-through throwaway systems, the various systems studied are ranked in order
of resource utilization as follows: the HWR on the LEU cycle; the HTGR and HTR-PBR
on either the LEU cycle or on the MEU/Th cycle; and the SSCR and PWR on the LEU cycle.
On the MEU/Th cycle the SSCR and PWR require more uranium than they do on the LEU
cycle and hence do not merit further consideration for once-through operation.
0 For once-through stowaway systems, in which the fissile material in the
spent fuel is expected to be recovered at some future date, the relative
ranking of the systems would depend on the ultimate destination of the
fissile material.
If future nuclear power systems are to be thermal
recycle systems, then early emphasis should be placed on reactors and
fuel cycles that have a high 233U discharge. If the future systems are
to be fast recycle systems, then emphasis should be placed on reactors
and fuel cycles that will provide a plutonium inventory.
0 For recycle systems utilizing thermal reactors, the preferred basic
fissile material is 233U. However, implementation of a 233U fuel cycle will
require an exogenous source of the fissile material; therefore, it is likely
that the MEU(235)/Th cycle would be implemented first to initiate the produc-
tion of 233U. Both the unburned 235U and the 233U would be recycled; thus the
system would evolve towards the MEU(233)/Th cycle, which is the denatured 233U
cycle as defined in this study. However, it is to be emphasized that these reac-
tors will not produce enough 233U to sustain themselves and separate 233U production
facilities must be operated. A Pu/Th-fueled thermal reactor has been considered
as a 233U production facility.
0 For recycle systems utilizing fast reactors, the preferred basic fissile
material is 239Pu. Using 233U as the primary fissile material or placing
thorium in the core sharply reduces the breeding performance of fast
reactors. However, fast reactors using plutonium fuel and thorium
blankets would be efficient 23 3U production facil i ties.