ORNL-5388 - the Molten Salt Energy Technologies Web Site

7-16
and overall fissile production (i.e., potential growth rate).
Table 7.2-6. Equilibrium Cycle Net Fissile Production for
Po ten ti a 1 LMFBR Transmuters*
Net Fissile
Production
Reactor - (kg/GWe - yp)
Core Axial Blanket Radial Blanket
Material Material Materi a1 Pu 233U Fissile
*Using values from Section 4.5-1 (~75% capacity factor). A more recent
study [Proliferation Resistant Large Core Design Study (PRLCDS)] indicates
that substantial improvements in the FBR performance is possible.
In addition to the systems utilizing the classical homogeneous core configuration,
systems utilizing a heterogeneous core configuration (i .e., interspersed fissile and
fertile regions) were examined as a possible means of improving the performance of fast
reactors operating on alternate fuel cycles. The substitution of different coolants
and fuel forms (i.e., carbides and metals versus oxides) were also considered. The net
effect of these changes is to increase the fuel volume fraction in the reactor core,
harden the spectrum, or, in some cases, both. The advanced fast reactor concepts show
significant improvement regarding the breeding ratio (and doubling time) relative to the
classical design when operating on alternate fuel cycles; however, the performance of the
alternate fuel cycles is still degraded over that of the same reactor type operating on
the Pu/~~*U cycle.
7.2.3. Symbiotic Reactor Systems
As has been stated throughout this report, in considering denatured 233U reactor
systems it is assumed that the denatured reactors will operate as dispersed power systems
supported by fuel cycle services and reactor transmuters located in secure energy centers.
When the system is in full operation no external source of fissile material is supplied;
that is, the system is self-contained. Initially the resource base (i.e., natural uranium)
can be used to provide a source of 233U for implementing the denatured 233U fuel cycle [via
the MEU(235)/Th cycle]; however, a shift to plutonium-fueled transmuters will eventually be
required. During this transition period, the system can be characterized by the rate at
which the resource base is consumed (see Chapter 6). In order to compare the long-term
potential of various reactor systems under the restrictions imposed by the denatured fuel
cycle, two system parameters have been developed: (1) the energy support ratio, defined
as the ratio of dispersed reactor power relative to the energy center (or centralized) power,
and (2) the inherent growth potential of the system. Since both the growth rate and the
energy support ratio involve fissile mass flows, they are interrelated. In order to unambig-
uously determine both parameters, the inherent system growth rate is determined at the
asymptotic value of the support ratio, a value which can be viewed as the "natural" operat-
ing ratio of the system.
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