ORNL-5388 - the Molten Salt Energy Technologies Web Site

3-24
3.3.4. Potential Circumvention of the Isotopic Barrier of Denatured Fuel
E. H, Gift and W. B. Arthur
Oak Ridae Gaseous Diffusion Plant
energy centers), many types of both fresh (unirradiated) and spent fuel may be in transit
throughout the world.
must meet the basic criterion that a sufficient quantity of fissile material cannot be
chemically extracted from seized elements for direct use in the fabrication of a nuclear
weapon.
If a large-scale denatured-uranium recycle program is fully implemented (with secure
238U to the fissile isotope 233U will prevent the direct use of the uranium in weapons
manufacture providing the 23% content of the uranium remains below a specified limit, which
for this study has been set at 12% (see Section 3.3.1).
chemically separated from the thorium fertile material included in the elements, it could not
be used for a weapon.
uranium would not be directly usable.
assumed that fuels containing both 233U and 235U will meet this criterion if their weighted
average lies between these limits.
In order to ensure that these fuels are proliferation resistant, they
As pointed out in previous sections of this report, the addition of the denaturant
Thus, even if the uranium were
Similarly, if the 235U content of uranium is kept below 20%, the
For the discussion presented here, it is further
With the chemical isolation of the primary fissile isotopes thus precluded, two poten-
tial means exist for extracting fissionable .material for the denatured fuel: (1) isotooic
separation of the fresh fuel into its 23% (or 235U) and 238U components; and (2) chemical
extraction from the spent fuel of the 239Pu bred in the 238U denaturant or chemical extraction
of the intermediate isotope 233Pa that would subsequently decay to 233U. In this examination
of the potential circumvention of the isotopic barrier of denatured fuel both these possibili-
ties are discussed; however, the probability of the second one actually being carried out is
essentially discounted.
Thus the emphasis here is on the possibility that would-be proliferators
would opt for producing weapons-grade uranium through the clandestine operation of an isotope
separation facility. For the purposes of this study it is assumed that the seized fuel is in
the form of fresh LWR elements of one of the following fuel types:
A.
B.
C.
D.
E.
Approximately 3% 235benriched uranium (same as currently used LWR fuel).
Recycle uranium from a thorium breeder blanket, denatured to %12% 233U with depleted
uranium.
Fifth-generation recycle of fuel type B with 233U fissile makeup from a thorium
breeder blanket.
First cycle of 235U-238U-Th fuel assuming no 233U is available from an external
source. In this fuel scheme the 235U concentration in uranium can be as high as 20%
(see above).
First recycle of fuel type D with 93% 235U in uranium makeup.
not all of the fuel in a reload batch will contain recycle uranium.
the reload batch will contain fuel type D.
tional" concept envisioned for plutonium recycle fuels.
In this fueling option,
Some portion of
This option is analogous to the "tradi-
It allows some of the fuel
L
h:
Id:
L
b'
c