ORNL-5388 - the Molten Salt Energy Technologies Web Site

4-14
Case G allows one possible means for utilizing the plutonium bred in the dispersed
reactors. Plutonium discharged from LEU-LWRs is used to provide the initial core fissile
requirements as well as the fissile makeup requirements. This plutonium is blended in a
U02 diluent consisting of natural or depleted uranium. The plutonium discharged from the
UO,/PuO, reactor is continually recycled - with two years for reprocessing and refabrication
- through the reactor. In the equilibrium condition, plutonium discharged from about
2.7 LEU-fueled LWRs can provide the makeup fissile Pu requirement for one U02/Pu02 LUR.
In Case H the Pu02/Th02 LWR also utilizes plutonium discharged from LEU-LWRs to
provide the initial core fissile requirements and the fissile makeup requirements. This
plutonium is blended in a Tho, diluent. The isotopically degraded plutonium recovered from
the PuO2/ThO2 LWR is blended with LEU-LWR discharge plutonium (of a higher fissile content)
and recycled back into the Pu02/Th02 LWR. Not only does this case provide a means of
eliminating the Pu bred in the dispersed reactors but, in addition, also provides for the
production of 233U that can be denatured and used to fuel dispersed reactors.
! The Pu02/Th02 LWR of Case I is similar to that in Case H in that plutonium discharged
from LEU-LWRs is used to provide the fissile requirements. However, the isotopically degraded
plutonium recovered from the PuO,/ThO, LWR is not recycled into an LWR but is stored for
later use in a breeder reactor.
Case J involves the use of highly enriched uranium blended with Tho2 to the desired
fuel enrichment. The uranium enrichment in HEU fuels was selected as 93.15 w/o on the basis
of information in Ref. 7. Initially all fuel consists of fresh HEU/Th fuel assemblies. Once
equilibrium recycle conditions are achieved, about 35% of the fuel consists of this fresh
makeup fuel, the remaining fuel assemblies in each reload batch containing the recycled (but
not re-enriched) uranium oxide blended with fresh Tho2.
Table 4.1-1 provides a summary, obtained from the detailed mass balance information,
of initial loading, equilibrium cycle loading, equilibrium cycle discharge, and 30-year
cumulative U308 and separative work requirements. All recycle cases involve a two-year
ex-reactor delay for reprocessing and refabrication. It is important to point out that for
cases which involve recycle of recovered fissile material back into the same LWR, in
"equi 1 ibrium" conditions the makeup requirement for a given recycle generation is greater
than the difference between the charge and discharge quantities for the previous recycle
generation because of the degradation of the isotopics. This is especially important in
Case H where, for example, the fissile content of the plutonium drops from about 71% to
about 47% over an equilibrium cycle.
Comparing Cases A and B of Table 4.1-1 indicates the penalties associated with implementation
of the MEU/Th cycle relative to the LEU cycle under the restriction of no recycle.
The MEU/Th case requires 40% more U308 and 214% more separative work than the LEU
c
I:
h: