Fuel processing spent reactor fuels

Research on removal of noble gases by permeation method with dimethyl silicon membranes was carried out in Oak Ridge National Laboratory [160]. On the basis of experimental work, the calculations for different industrial cascades separating krypton and xenon from the space of molten salt and sodium cooled breeder reactor or from the off gas from a plant processing spent reactor fuel were performed. 

Nuclear Waste Reprocessing. Liquid waste remaining from processing of spent reactor fuel for military plutonium production is typically acidic and contains substantial transuranic residues. The cleanup of such waste in 1996 is a higher priority than military plutonium processing. Cleanup requires removal of long-Hved actinides from nitric or hydrochloric acid solutions. The transuranium extraction (Tmex) process has been developed for... 

The solvent extraction process that uses TBP solutions to recover plutonium and uranium from irradiated nuclear fuels is called Purex (plutonium uranium extraction). The Purex process provides recovery of more than 99% of both uranium and plutonium with excellent decontamination of both elements from fission products. The Purex process is used worldwide to reprocess spent reactor fuel. During the last several decades, many variations of the Purex process have been developed and demonstrated on a plant scale. 

National Program for Pyrochemical and Dry Processing of Spent Reactor Fuel... 

Barghusen, J. J., et al. Fluid-Bed Fluoride Volatility Processing of Spent Reactor Fuel Materials, in Progress in Nuclear Energy, series III, Process Chemistry, vol. 4, Peigamon, New York, 1970, p. 347. 

About 0.5 kg is contained in each ton of spent reactor fuel. By sq>aration processes, similar to those described in Giapter 21, hundreds of kg of Np has been made available for research. So far it has not found any practical use except as target material for production of Pu. Though Np has too short a half-life to still exist naturally on earth, its optical spectrum has been observed in some stars, from which the star can be deduced to be of relatively young age ( 10 y, cf. next on Pu). 

Once the radioactive fission products are isolated by one of the separation processes, the major problem in the nuclear chemical industry must be faced since radioactivity cannot be immediately destroyed (see Fig. 10-7c for curie level of fission-product isotopes versus elapsed time after removal from the neutron source). This source of radiation energy can be employed in the food-processing industries for sterilization and in the chemical industries for such processes as hydrogenation, chlorination, isomerization, and polymerization. Design of radiation facilities to economically employ spent reactor fuel elements, composite or individually isolated fission products such as cesium 137, is one of the problems facing the design engineer in the nuclear field. 

Factors are for direct-maintenance plants processing enriched spent reactor fuels. 

Unirradiated material does not contain substantial amounts of fission products thus it requires less time and effort to be converted to components of nuclear explosive devices than irradiated direct use material like spent reactor fuel. Indirect use material (DU, NU, LEU and Th) must be further processed to produce direct use material. 

Plutonium is handled and processed in spent reactor fuel-reprocessing plants, in MOX (Pu02, UO2) fuel fabrication plants, and in research centers where transmanium elements are studied. Large-scale reprocessing of irradiated uranium and uranium-plutonium fuels is performed to recover and purify uranium and plutonium either for further use in nuclear reactors or, in the case of plutonium, in nuclear weapons. The principal uranium and plutonium products are found in Table 14.6. 

Fuel reprocessing (recycling) The processing of reactor fuel to separate the unused fissionable material from waste material. Reprocessing extracts isotopes from spent fuel so they can be used again as reactor fuel. 

Perhaps there should be centralized areas for storage of spent fuel from present reactor types. These storage areas should be adjacent to reprocessing plants which would be built to process the spent fuel to provide the new fuel for the Fast Reactors going on line. 

In 1942, the Mallinckrodt Chemical Company adapted a diethylether extraction process to purify tons of uranium for the U.S. Manhattan Project [2] later, after an explosion, the process was switched to less volatile extractants. For simultaneous large-scale recovery of the plutonium in the spent fuel elements from the production reactors at Hanford, United States, methyl isobutyl ketone (MIBK) was originally chosen as extractant/solvent in the so-called Redox solvent extraction process. In the British Windscale plant, now Sellafield, another extractant/solvent, dibutylcarbitol (DBC or Butex), was preferred for reprocessing spent nuclear reactor fuels. These early extractants have now been replaced by tributylphosphate [TBP], diluted in an aliphatic hydrocarbon or mixture of such hydrocarbons, following the discovery of Warf [9] in 1945 that TBP separates tetravalent cerium from... 

The baseline process, including the pressure sintering step, was demonstrated with both simulated high level waste and under hot cell conditions using a waste solution prepared from typical spent light water reactor fuel. A batch contacting method using sodium titanate was also evaluated, but the overall decontamination factor was much lower than obtained in the column process. 

Spent fuel from a reactor contains unused uranium as well as plutonium-239 which has been created by bombardment of neutrons during the fission process. Mixed with these useful materials are other highly radioactive and hazardous fission products, such as cesium-137 and strontium-90. Since reprocessed fuels contain plutonium, well suited for making nuclear weapons, concern has been expressed over the possible capture of some of this material by agents or terrorists operating on behalf of unfriendly governments that do not have a nuclear weapons capability. 

Processes for the isolation and purification of plutonium, including the enrichment of spent nuclear reactor fuels, arc described in the entry on Nuclear Power Technology. These processes take advantage of Pu s several oxidation states, each of which has different chemical properties. The processes may involve carrier precipitation, solvent extraction, and ion exchange. 

Spent nuclear fuel is still radioactive and consists of a mixture of uranium and fission products. Nuclear reactor waste can be processed and some of it reused, but the percentage processed depends on the price of uranium. When the price is low, as it was in the late 1990s, most nuclear waste is simply stored without further processing. 

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