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6.2.6 Converter-Breeder System with Light Plutonium "Transmutation"
The results presented in the preceding sections have demonstrated that nuclear
power systems based on converter reactors will ultimately be limited by the quantity of
economically recoverable uranium.
While a larger U308 resource base will allow larger
systems to develop, the converse is also true. Since the U308 resource base has always
been somewhat uncertain, the deployment of fast breeder reactors has traditionally been
considered as the method by which the consequences of this uncertainty would be minimized.
Thus, it has historically been assumed that by deploying'FBRs nuclear power systems would
outgrow the constraints naturally imposed by the U308 resource base.
In the option discussed here (Option 6), an FBR with a plutonium-uranium core and a
thorium blanket is located in the energy center to produce 233U which is then used in de-
natured converter reactors outside the center.
rate could be obtained with a plutonium-thorium core in the FBR, this option is referred
to as having a Zight "Pu-~o-~~~U" transmutation rate.
contained in this option are shown in Fig. 6.1-4.
Because a higher plutonium "transmutation"
The individual reactor concepts
The nuclear contribution associated with this option when all the converters utilized
are LWRs (Case 6L) is shown in Fig. 6.2-29. In this case, even with the high-cost U308
supply, the system is capable of maintaining a net addition rate of 15 GWe/yr throughout
the planning horizon - i.e., from 1980 through 2050. The ability of the nuclear system
to maintain this net addition rate is a direct consequence of the compound system doubling
time of the FBR, which, in this case, is 13 yr. This doubling time in turn is a direct
consequence of the FBR having a Pu-U core.
In this option the installed nuclear capacity which must be located in energy centers
increases as a function of time to approximately 560 GWe in year 2050 (see Fig. 6.2-30).
The most rapid increase occurs between 2010 and 2020 as the number of FBRs on line in-
creases significantly. The amount of nuclear capacity available for installation outside
the centers increases from approximately 300 GWe in year 2000 to over 500 GWe in year 2050.
Initially, the LWR loaded with approximately 3% enriched 235U is the principal reactor
available, but as the U308 is depleted, it is replaced by the LWR loaded with 11% 233U
in 238U. This is illustrated in Fig. 6.2-31, which also indicates that this option is
capable of maintaining an energy support ratio greater than unity throughout the planning
horizon.
The maximum annual U308 and enrichment requirements for this case are 62,000 !jT/yr
and 44 million SWUlyr, respectively. These annual requirements do not differ significantly
from those obtained with the LWR on the throwaway cycle, the reason being that in either
case, the goal of the nuclear power system is to maintain a net addition rate of 15 GWe/yr
provided this increase can be sustained by the U308 supply.
The maximum installed capacity