ORNL-5388 - the Molten Salt Energy Technologies Web Site

4-8
Since with the exception of the Fort St. Vrain HTGR, the existing power reactors in
the United States are LWRs, initial studies of alternate fuel cycles have assumed that they
would first be implemented in LWRs.* Thus the calculations for LWRs, sunnnarized in Sec-
tion 4.1 have considered a number of fuels. For the purposes of the present study the fuels
have been categorized according to their potential usefulness in the envisioned power system
scenarios. Those fuel types that meet the nonproliferation requirements stated earlier in
this report are classified as "dispersible" fuels that could be used in LWRs operating outside
a secure energy center. The dispersible fuels are further divided into denatured 233U
fuels and 235U-based fuels. The remaining fuels in the power systems are then categorized as
"energy-center-constrained" fuels. Finally, a fourth category is used to identify "reference"
fuels. Reference fuels, which are not to be confused with an individual reactor's reference
fuel , are fuels that would have no apparent usefulness in the energy-center, dispersed-reactor
scenarios but are included as limiting cases against which the other fuels can be compared.
(Note: The reactor's reference fuel may or may not be appropriate for use in the reduced
proliferation risk scenarios.)
To the extent that they apply, these four categories have been used to classify all
the fuels presented here for the various reactors. Although the contributing authors have
used different notations, the fuels included are in general as follows:
Dispersible Resource-Based Fuels
A. Natural uranium fuel (containing approximately 0.7% 235U), as currently used in
CANDU heavy-water reactors. Notation: U5(NAT)/U.
B.
C.
Low-enriched 235U fuel (containing approximately 3% 235U), as currently used in
LWRs. Notation: LEU; U5(LE)/U.
Medium-enriched 235U fuel (containing approximately 20% 235U) mixed with thorium
fertile material; could serve as a transition fuel prior to full-scale implementation
of the denatured 233U cycle. Notation: MEU(235)/Th; DUTH(235).
Dispersible Denatured Fuel
D. Denatured 233U fuel (nominally approximately 12% 233U in U). Notation: Denatured
233U; ' denatured uranium/thorium; denatured 233U02/Th02; MEU(233)/Th;
DUTH(233); U3(DE)/U/Th.
233U/23*U;
*NOTE: The results presented in this chapter do not consider the potential improvements
in the once-through LWR that are currently under study. In general, this is also true
for the resource-constrained nuclear power systems evaluated in Chapter 6; however,
Chapter 6 does include results from a few calculations for an extended exposure
(43,000-MWD/MTU) once-through LEU-LWR. The particular extended exposure design con-
sidered requires 6% less U3O8 over the reactor's lifetime.
b;
tl;
c
i:
c