Highly active waste nuclear fuel reprocessing

In a test at Mayak nuclear fuel reprocessing plant in Russia, alkaline high-active waste was subjected to extraction by a mixture of parent /-butyl calix[6]arene, 2- [bis(2-hydroxyethyl)amino]methyl -4-alkylphenol, and a solubilizer in dodecane. 

Some countries, e.g., France, Japan, Russia, and the United Kingdom have chosen to reprocess their spent nuclear fuel to recycle uranium and plutonium as nuclear fuel and to obtain a high active waste (HAW) firaction that is less radiotoxic than the spent fuel itself. In this process, very high separation factors are necessary. The fission product activity has to be reduced by a factor of > 10 and the separation factor between uranium and plutonium must be at least 2 x lO. All full-scale reprocessing processes are based on solvent extraction, and today the plutonium uranium redox extraction (PUREX) process dominates the market completely. 

Nuclear fuel reprocessing operations produce both high and medium level activity liquid wastes (HLW/MLW). The major nuclides in these radioactive wastes are those with long half-lives, mainly / /7 emitters such as Tc, I, Zr, Se, Cs, etc., or a emitters such as transuranics Np, Pu, Am, Cm, etc. [1]. That is why great efforts have been devoted throughout the world to propose harmless storage of these wastes. 

In the past ten years the number of chemistry-related research problems in the nuclear industry has increased dramatically. Many of these are related to surface or interfacial chemistry. Some applications are reviewed in the areas of waste management, activity transport in coolants, fuel fabrication, component development, reactor safety studies, and fuel reprocessing. Three recent studies in surface analysis are discussed in further detail in this paper. The first concerns the initial corrosion mechanisms of borosilicate glass used in high level waste encapsulation. The second deals with the effects of residual chloride contamination on nuclear reactor contaminants. Finally, some surface studies of the high temperature oxidation of Alloys 600 and 800 are outlined such characterizations are part of the effort to develop more protective surface films for nuclear reactor applications. ... 

Radioactive wastes of concern include wastes that result from operation of the nuclear fuel cycle (mining, fuel fabrication, reactor operation, spent fuel reprocessing, and waste storage), from nuclear weapons testing, and from medical and research activities. In recent years, the emphasis has been on predicting the behavior of disposed high-level wastes in deep geologic... 

Two papers about high-level waste management plans for commercial reprocessing plants complete the overview of operating plant activities. J. P. Duckworth details the Nuclear Fuel Services plans. R. G. 

The americium and curium isotopes formed during irradiation of nuclear reactor fuels are diverted into the high-level waste (HLW) stream during fuel reprocessing. The HLW is thus the biggest potential source for these elements, and R+D activities to develop a process for the recovery of Am and Cm from HLW were started in 1967. A major condition was that the process to be developed must not essentially increase the waste amount to be processed further, must not use strongly corrosive reagents, and must be compatible with the final waste solidification procedure. 

Natural zeolites have played important roles as in clean-up from nuclear accidents. After the Three Mile Island incident, the SDS (Submerged Dcmineraliser System) made use of a 60/40 mixture by volume of IE-96 and LTA zeolite (A-51) from the then Union Carbide Corporation to immobilise 340,000 Ci of fission products from >1.5 million gallons of water [128], Phillipsite tuff, from Pine Valley Nevada, clinoptilolite, A-51, and IE-96 have all been used at pilot plant scale to deal with high salt, high activity, aqueous wastes at West Valley, New York- site of the PUREX plant used for reprocessing nuclear fuels from 1966 to 1972. 

The design and evaluation of nuclear waste forms requires some understanding of the sources, volumes, compositions and activities of the various waste streams generated by the nuclear fuel cycle. There are three primary sources of radioactive waste in the United States (DOE 1997) the high-level waste (HEW) from the reprocessing of spent nuclear fuel, the spent nuclear fuel itself, and plutonium reclaimed by reprocessing or obtained by the dismantlement of nuclear weapons. 

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