ORNL-5388 - the Molten Salt Energy Technologies Web Site

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To further specify the plant, it can be assumed that the diverter would like to:
1. Minimize the feed and waste stream flows in the first and second cascades consistent
with limiting the number of centrifuges required.
2. Achieve a significant weapons-grade product flow rate. (A flow rate of 100 kg U/yr
having a fissile content of 90% 233U t 235U was chosen.)
3. Reduce the 232U content in the metal product so that contact manufacture can be
achieved without serious radiation hazard.
Based on these assumptions and considering the fuel types listed in Table 3.3-2,
a series of enrichment cascades, flows and selected isotopic parameters are presented
in Table 3.3-7. The basic criterion chosen for the final uranium product was that the
232U concentration was about 1 ppm 232U in total uranium.
emission rate from the final metal product is sufficiently low that most fabrication
and subsequent handling operations can be carried out in unshielded facilities using
contact methods.
At this level the gama
The first enrichment cascade to perform the separation of 232U from the remaining
uranium w ill be very radioactive. But it will be only slightly more radioactive than if
only one cascade were used and the z32U not separated from the final product. The table
shows that a factor of two increase in Z32U product concentration will provide sufficient
decontamination without a prohibitive increase in the number of centrifuges. If much
greater (by a factor of 20) concentrations of 232U can be tolerated in the cascade, some
reduction (420 to 30%) can be made in the necessary number of centrifuges.
Table 3.3-7 also shows a striking difference in the number of centrifuges required
to decontaminate the uranium product when the uranium makeup to the thorium cycles is 93%
235U rather than 2331) from the thorium breeder blanket. This results because with the
235U recycle fuel it is more advantageous, both in centrifuges and in annual feed require-
ments, to design the separation to throw away in the first cascade waste stream much of
the 233U and 2341) in addition to the 232U. Thus, the fissile content in the final product
from these fuel mixtures is nearly all 235U.
As a better means of measuring the proliferation potential of the different fuel
mixtures, the data presented in Table 3.3-7 have been recast in Table 3.3-8 as a
function of three parameters: (1) the number of centrifuges needed, (2) the uranium
feed requirements to produce 100 kglyr of 90% fissile uranium and (3) the number of
standard Westinghouse PWR fuel assemblies that must be diverted.
Based on these criteria, the following conclusions can be drawn with respect to
desirability of fuels for diversion: