ORNL-5388 - the Molten Salt Energy Technologies Web Site

the system becomes less and'less dependent upon uranium ore and more and more upon
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plutonium, the energy support ratio will approach zero.
*
The denatured fuel cycle Cases 4L, 5L, and 6L are compared with the throwaway cycle
in Fig. D-2e. Nuclear market penetration for plutonium throwaway (Case 4L) is not substantially
greater than for the throwaway cycle (Case 1L). The peak penetration is about
630 GWe of installed nuclear capacity versus 500 GWe for the throwaway cycle. However,
if the plutonium is utilized in an LWR Pu/Th converter (Case 5L), the maximum nuclear
penetration is 1000 GWe, which is a factor of two greater than for the throwaway cycle
and, furthermore, the peak does not occur until more than 10 years later. Introduction
of the FBR with a Pu-U core and thorium blankets (Case 6L) results in a peak penetration
of 1250 GWe in about 2025. After 2025, the nuclear market fraction is constant because
the system is essentially independent of uranium, which is becoming increasingly more
expensive.
With respect to U308 utilization, Fig. D-2e shows that the Pu/Th converter case has
slightly better ore utilization (by 7%) than classical plutonium recycle in LWRs (Case 2L
in Fig. D-2b). Furthermore, plutonium "transmutation' in Pu-U FBRs also has better U308
utilization (by 12%) than classical plutonium recycle in FBRs (compare Cases 3L and 6L).
The reason for these trends is that the 233U fuel that is being bred is worth more as a fuel
in thermal reactors than the plutonium that is being destroyed.
The effect of a larger uranium supply on the market penetration for converters and
FRBs that produce *3% is shown in Figs. D-2f and D-29. For both cases (5 and 6), the
large uranium supply increased the maximum nuclear penetration by about 450 GWe. Case 7L
introduced a denatured 233U-fueled FER to the 6L case, and Case 8L is identical to Case
7L except that the FBR with a Pu-U core is replaced with an FBR with a Pu-Th core. The
maximum nuclear penetration for Cases 7L and 8L are compared with 6L in Fig. D-2h. The
denatured 23%-fueled FBR doesn't have any impact because this reactor is competing with
less expensive 233U-fueled LWRs and therefore isn't built. The nuclear market penetration
for Case 8L is seen to decrease after about 2020. This is because the neutronics
properties of FBRs fueled with Pu-Th are degraded significantly from those fueled with
Pu-U.
As a result, the doubling time of these reactors is longer and the cost is higher.
The degraded neutronics of the Pu-Th FBRs are reflected in the U308 utilization of Case
8L where the ore usage per GWe is almost 50% higher than for Case 6L.
The objective in building FRBs with Pu-Th cores is to increase the 23% production
and therefore the ratio of reactors located outside the energy center to those inside the
* The nuclear reactors that are available in Case 5L with nuclear-fossil competition are
similar to Case 5UL described in the other sections of this report. However, in 5L the
denatured 235U-fueled LWR isn't built because of economics. Therefore, the solution
more closely resembles Case 5TL.
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