Recycling plutonium

If the economics of recycling were improved, that option would become preferable for spent fuel because the permanent repository issues of the residual fission products would be simpler. The economic value of the energy generated from the recycled plutonium and uranium would substantially allay the costs of the repository as compared to the spent fuel throwaway option. 

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. 

Figure 3.32 Fuel-cycle flow sheet for 1000-MWe LWR fueled with natural uranium, recycle plutonium, and plutonium recovered from reactor fueled with enriched uranium. Basis 1 year, 80 percent capacity factor.

Reactor type Fuel PWR Uranium (3.3% U) PWR Uranium and recycled plutonium HTGR U, thorium, and recycled uranium LMFBR Uranium and recycled plutonium... 

The effect of plutonium recycle is to increase the production of higher-mass isotopes of plutonium and of americium and curium, because the recycled plutonium is exposed to neutrons throughout the entire irradiation cycle. The actinide quantities calculated [PI] for the same 1000-MWe reactor operating on an equilibrium fuel cycle with self-generated plutonium recycle are shown in Table 8.5. The alpha activity of the plutonium processed yearly is increased by a factor of 14 by plutonium recycle, the americium activity is increased by a factor of 5, and the curium activity by a factor of 7. 

Table 8.15 (a, n) surface dose from light elements in recycled plutonium and uranium... 

Many countries are planning to recycle plutonium in LWRs as MOX fuel ( 30% of the core or even as full MOX loading). This recycling scheme can stabilize the plutonium accumulation. 

However, in the case of mixed oxide fuel, the new fuel may be radioactive as a result of the recycled plutonium it contains and, in some fuels, recycled uranium may be used. In this case, the new fuel will be a significant source of both neutrons and gamma rays and it will need to be shielded and contained at all times until it is inserted into the reactor. The magnitude of the neutron source term will depend upon the time that has elapsed since the plutonium was created, since actinides that emit neutrons will be produced as the plutonium decays. 

The period 1985 - 1998 has seen substantial technical advances. Chief among these has been the demonstration of reliable operation by the BN-600 plant, and the reliable operation of fuel at high bumup. In PFR large numbers of mixed-oxide fuel pins reached more than 15 % bumup without failure, and several reached 20 % bumup with an irradiation dose in excess of 130 displacements per atom (dpa) in the cladding. These results have been confirmed and surpassed by irradiations in Phenix to more than 160 dpa. The fuel cycle, based on mixed oxide fuel and PUREX reprocessing, has been closed in that plutonium fi om irradiated fuel has been separated, fabricated into new fuel and recycled to the reactor for further use. In the USA bumup of up to 20 % has been achieved in ternary alloy U - Pu - Zr metal fuel. The basic technology of the use of fast reactors to breed and recycle plutonium in a commercially acceptable manner has thus been demonstrated. 

Some experts claim that recycling plutonium in the form of MOX fuel helps combat nuclear prohferation by burning it in the reactor, whereas other experts claim that isolating, handhng, and storing plutonium should be prohibited, because it could be easily diverted by terrorists. The ambition of Gen-IV in this domain focuses on two breakthrough technologies ... 

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