ORNL-5388 - the Molten Salt Energy Technologies Web Site

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4-3
4.0. INTRODUCTION
L. S. Abbott, T. J. Burns, and J. C. Cleveland
Oak Ridge National Laboratory
The three preceding chapters have introduced the concept of 233U fuel and its use in
nuclear power systems that include secure (guarded) energy centers supporting dispersed power
reactors, the rationale for such systems being that they would allow for the production and
use of fissile material in a manner that would reduce weapons proliferation risks relative
to power systems that are increasingly based on plutonium-fueled reactors. Throughout the
discussion it has been assumed that the use of denatured 233U fuel in power reactors is
feasible; however, up to this point the validity of that assumption has not been addressed.
A number of calculations have been performed by various organizations to estimate the
impact that conversion to the denatured cycle (and also to other "alternate" fuel cycles)
would have on power reactors, using as models both existing reactors and reactors whose
designs have progressed to the extent that they could be deployed before or shortly after
the turn of the century. This chapter presents pertinent results from these calculations
which, together with the predictions given in Chapter 5 on the availability of the various
reactors and their associated fuel cycles, have been used to postulate specific symbiotic
nuclear power systems utilizing denatured fuel. The adequacy of such systems for meeting
projected electrical energy demands is then the subject of Chapter 6.
The impact of an alternate fuel cycle on the performance of a reactor will, of
course, be reactor specific and will largely be determined by the differences between the
neutronic properties of the fissile and fertile nuclides included in the alternate cycle
and those included in the reactor's reference cycle.
fuel, the fissile nuclide is 233U and the primary fertile nuclide is 232Th, with fertile
238U included as the 233U denaturant. If LWRs such as those currently providing nuclear
power in the United States were to be the reactors in which the denatured fuel is deployed,
then the performance of the reactors using the denatured fuel must be compared with their
performance using a fuel comprised of the fissile nuclide 23% and the fertile isotope
238U.
denatured fuel must also be compared with LWRs in which Pu is recycled. Similarly, if
FBRs were to be the reactors in which the denatured fuel is deployed, then the performance
of FBRs operating on 233U/238U or 233U/238U/232Th and including 232Th i n their blankets
must be compared with the performance of FBRs operating on surrounded by a 238U
blanket.
In the case of the proposed denatured
And since the use of 233U assumes recycle, then the performance of the LWRs using
A significant poht in these two examples is that they represent the two generic
types of power reactors -- thema2 and fast -- and that the neutronic properties of the
fissile and fertile nuclides in a thermal-neutron environment differ from their properties
in a fast-neutron environment. Thus while one fissile material may be the optimum fuel in
a' reactor operating on thermal neutrons (e,g., LWRS) it may be the least desirable fuel
for a reactor operating on fast neutrons (e.g., FBRs).