Fissile materials recycling

The recycle weapons fuel cycle rehes on the reservoir of SWUs and yellow cake equivalents represented by the fissile materials in decommissioned nuclear weapons. This variation impacts the prereactor portion of the fuel cycle. The post-reactor portion can be either classical or throwaway. Because the avadabihty of weapons-grade fissile material for use as an energy source is a relatively recent phenomenon, it has not been fully implemented. As of early 1995 the United States had purchased highly enriched uranium from Russia, and France had initiated a modification and expansion of the breeder program to use plutonium as the primary fuel (3). AH U.S. reactor manufacturers were working on designs to use weapons-grade plutonium as fuel. 

Nuclear fuel reprocessing was first undertaken with the sole purpose of recovering plutonium, for weapons use, from uranium irradiated in nuclear reactors. These reactors, called the production reactors, were dedicated to transmuting as much of the uranium as possible to plutonium. From its original scope of recovering exclusively plutonium, with no attempts to either recover or recycle uranium, nuclear fuel reprocessing has since grown into a much more sophisticated and complex operation with expanded scope. It is now called upon to separate uranium and plutonium from the fission products, and to purify these elements to levels at which these fissile materials can be conveniently recycled for reuse. The present scope also extends to fission products separation and concentration. 

The nuclear fuel cycle is a set of steps in the processing of the reactor s fissile materials that begins with the mining of uranium and extends through the final disposition of the waste from the reactor. These steps are referred to as a cycle because it is possible that the material taken from the reactor after use can be recycled. A schematic diagram of the nuclear fuel cycle is shown in Figure 16.1. 

Sound Resource Utilization. (a) Plutonium can be safely recycled without risk of proliferation instead of being discarded, (b) Rapid recycle of short-cooled fuel reduces the total demand for fissile material in the fuel cycle. 

In the FBR fuel cycles, the fraction (i.e., 21% in the examples above) of the blanket fuel recycled for use in refabricating driver fuel after AIROX processing only depends on the concentration of fissile material in the Civex or Pyrocivex product. As the fissile content of the Civex or Pyrocivex product is decreased, the amount of blanket fuel recycled for driver fuel fabrication must also be decreased proportionately and the amount of spent blanket fuel processed by the Civex or Pyrocivex process must be increased. 

Besides being proliferation resistant, the other advantages of fuel cycles using AIR0X reprocessing are (1) extension of uranium reserve by recycling the fissile material in spent fuel,... 

Potential diversion of nuclear material from power production to weapons production by national or subnational groups has resulted in a reevaluation of the proliferation resistance of various fuel cycles. The low-contamination fuel cycle, utilizing AIROX dry processing, is proliferation resistant due to the retention of fission products with the fuel and to the low concentration of fissile material in all process steps. In the AIROX process, UO2 is oxidized with air to U3O8 to expand the fuel volume which simultaneously declads and pulverizes the fuel the fuel is subsequently reenriched, repelletized, and recycled to the reactor. 

Fuel Recycle Requirements. We asstime that the final product returned for fuel fabrication and recycle is a mixed uranium-plutonium dioxide material, partially decontaminated from fission products. The questions of fissile material enrichment, radiation levels, and required handling facilities are not addressed. 

In part III of Fig. 1.11, the recovered uranium is recycled and reenriched and the recovered plutonium is recycled to provide part of the fissile material in the reactor fuel assemblies. Two kinds of fuel assemblies are used. One kind is the same as used in cases I and II, which consist of UO2 enriched to 3.3 w/o The annual feed rate of these assemblies is 18.3 MT of enriched uranium. The other kind consists of mixed uranium and plutonium dioxides, in which the uranium is in the form of natural UO2. Their annual feed rate is 8.9 MT of heavy metal (uranium plus plutonium), including 445 kg of recycle plutonium. The total annual UjOg feed rate is 160 short tons, which is less than for the heavy-water reactor of Fig. 1.10. 

Transuraniums generated hy fuel huming include fissile material (e.g., Pu and Pu) and fertile material (e.g., Pu, Pu, and minor actinides), separated and recovered in a fuel cycle facdity, and then recycled as fuel materials. Basically, transuraniums are assumed to he transmuted into fissUe materials in a reactor at some stage and eventually to undergo fission reactions. 

In terms of neutron spectrum and fuel cycle, there are two options of the SCWR the first is a thermal neutron reactor, and the second is an FR-based closed fuel cycle coupled with full actinide recycle based on advanced aqueous processing. Using last neutrons will be advantageous for achieving sustainability to be aimed for the Generation IV reactor because of their potential to produce at least as much fissile material as it consumes. 

In Italy, the intention was to develop a reactor that was independent of eruiched fuel, while in Japan the HWR was seen as part of a future fuel recycling strategy where spent fuel from PWRs would be recycled through HWRs to make use of the fissile material remaining in the fuel. 

Using a recycle strategy can extend the resource base by breeding fissile material from fertile U and/or Mh — a strategy that might be required at an industry scale slightly before mid century. 

The fast neutron spectrum with transuranic nitride fuel and lead coolant is fissile self sufficient with a core conversion ratio of unity. This enables a closed fuel cycle based upon a fertile feed stream of depleted or natural uranium and a minimal volume waste stream comprised only of fission products. All fissile material including minor actinides is recycled in the fabrication of new fuel cores and is burned as fuel in STAR reactors. 

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