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4-1 9
4.1.2. Boiling Water Reactors
Mass flow calculations for BWRs presented in this chapter were performed by
General Electric.
A description of the fuel assembly designs developed by General
Electric for the utilization of thorium is presented in Ref. 8.
been analyzed:
Dispersible Resource-Based Fuels
A. LEU, no recycle.
The following cases have
6. MEU/Th, KO rec.vcle.
B'. LEU/Th mixed lattice (LEU and Tho2 rods), no recycle.
R". LEU/)?EU/Th mixed lattice (L€U/Th, MEU/Th, and Tho2 rods), no recycle.
D. LEU/MEU/Th mixed lattice, recycle of uranium, 235U makeup.
Dispersible Denatured Fuel
E. Denatured 233U, recycle of uranium, a33U makeup.
Enerqu-Center-Constrained Fuels
F. LEU, recycle of uranium and self-generated plutonium, 235U makeup.
G. PU/~~~U, recycle of plutonium, plutonium makeup.
H. Pu/~~~T~, recycle of plutonium, plutonium makeup.
Case A represents the current mode of BWR operation. Case B involves the replacement
of the current LEU fuel with MEU/Th fuel in which the initial uranium enrichment is limited
to 20% 235U/238U. Cases B' and B" represent partial thorium loadings that could be
utilized as alternative stowaway options. In Case B' a few of the LEU pins in a
conventional LEU lattice are replaced with pure Tho2 pins, while in Case B" some LEU
pins in a conventional lattice are replaced by MEU/Th pins and a few others are replaced
with the pure Tho, pins. These cases are in contrast with Case B in which a "full" thorium
loading is used (U02/Th02 in every pin). Case D represents the extension of Case B" to
the recycle mode; however, only the uranium recovered from the Th-bearing pins is recycled.
Cases F-H represent possible fissile/fertile combinations for use in secure energy centers.
Table 4.1-5 provides a summary of certain mass balance information for BWRs operating
on these fuel cycles. All recycle cases involve a two-year ex-reactor delay for repro-
cessing and refa bri cation.
As was shown in Table 4.1-1 for PWRs, the introduction of thorium into a BWR core
inflicts a penalty with respect to the resource requirements of the reactor (compare
U308 and SWU requirements of Cases A and 6). However, as pointed out above, Case B is
for a full thorium loading.
represented by Cases 6' and 6" a much smaller fissile inventory penalty results from
the introduction of thorium in the core.
PWRs. )
In the two General Electric fuel assembly designs8
(Similar schemes may also be feasible for