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[en] The technology of SNF management in molten salts currently developed by a group of institutes headed by RIAR has had several stages of development: - basic research of uranium, plutonium and main FP properties (investigation and reprocessing of different kinds of SNF in 1960 - 1970); - development of the equipment and implementation of the pyro-electrochemical technology of granulated UPu fuel production. Development of the vibro-packing method and in-pile testing of vibro-packed fuel pins with granulated fuel as the most 'logical' continuation of reprocessing: implementation of the technology for BOR-60 and BN-600 (1980 - 1990); - development of closed fuel cycle elements. Checking of the technology using batches of SNF. In-pile tests. Feasibility study of the closed fuel cycle (CFC). Study of application of the technology to other objects (transmutation; nitride, cermet and other fuels) (1980 - 1990). The current status of the research is the following: - Basic research. Properties of uranium, plutonium, thorium, and neptunium in chloride melts have been studied in much detail. The data on physical chemistry and electrochemistry of the main FP is enough for understanding the processes. Detailed studies of americium, curium, and technetium chemistry are the essential investigation directions; - Engineering development. The technology and equipment bases have been developed for the processes of oxide fuel reprocessing and fabrication. The technology was checked using 5500 kg of pure fuel from different reactors and 20 kg of irradiated BN-350 and BOR-60 fuel. The bases of the technology have been provided and the feasibility study has been carried out for a full-scale plant of BN-800 CFC; - Industrial application: Since the technology is highly prepared, the activities on industrial application of U-Pu fuel are now underway. The BOR-60 reactor uses fuel obtained by the dry method, the design of the facility for implementation of CFC reactors is being developed. 9 FAs have been tested and 3 FAs are being irradiated in the BN-600 reactor. The facilities for production of U-Pu fuel of the BN-600 hybrid core are being modernized. Apart from the main technology of oxide fuel reprocessing and production, new dry processes are being studied: - obtaining of oxide fuel with neptunium and americium (for transmutation); - reprocessing of nitride fuel (for the BREST closed fuel cycle); - reprocessing of uranium fuel from research reactors (in order to solve the problem of unconventional SNF management); - metallization of oxide fuel for long-term storage. The work performed in RIAR is actively supported by Japanese organizations; RIAR cooperates with France, the Republic of Korea, and the USA. (authors)

[en] Data on behavior of plutonium fluoride and fission products (FP) dissolved in fuel composition are needed to calculate the duration of an operating cycle of the ADTT facility (Accelerator-Driver Transmutation Technologies) and to determine the effect of their equilibrium concentrations on nuclear-physical characteristics of reactor operation. The data on the FP fluoride solubility in the molten salts are of great important for some industrial processes (electrolytical metal deposition, development of physical-chemical mean for processes of chemical technology, etc.) As noted above, some information on this question is given in monography and articles. Data concerning fluoride salts are given in reports. However, it was impossible to make the substantial analysis of mutual solubility of fluoride melts. The primary investigation of CeF₃ and neodymium, samarium and lanthanum fluorides showed that the solubility of the melt LiF-BeF₂ and LiF-BeF₂-ThF₄ was a linear function of reverse temperature and increases from lanthanum to samarium in the row of rare-earth elements. Disagreement in estimation of plutonium trifluoride solubility and incomplete data on the solubility of rare-earth elements prompted this study

[en] Composition, properties and outputs of high-active products and waste have been studied after pyro-electrochemical reprocessing of BN-350 and BOR-60 reactor irradiated MOX fuel. The main amount of fission products, actinides and impurities is concentrated in a small volume of solid recycled products - uranium dioxides of two types and high-active waste - phosphate deposit and spent salt electrolyte. The phosphate deposit and electrolyte are subject to the final disposal but uranium dioxides are returned to the cycle after a certain period of storage. Based on the study of waste properties it was concluded that they can be kept in sealed stainless steel containers without treatment for a long time. Both types of waste may be immobilized in phosphate glass or in monazite-type and kosnarite-type (NZP) ceramics to make an additional safety barrier before the final disposal. (authors)

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[en] The report summarizes the experience on developing and operating in RIAR's Chemical Technology Division a versatile stand designed for obtaining of experimental data on the process parameters of the currently developed non-aqueous processes of nuclear fuel management and on the peculiarities of the test equipment operation. The experiments carried out at the Stand according to the process requirements and the requirements of the equipment remote servicing are maximally approximated to the experimental processes with real irradiated fuel. The versatility of the Stand allows accomplishing a wide range of experimental tasks including those related to investigation of the processes for implementation of the closed fuel cycle. The report presents the data on the Stand structure and interior arrangement as well as on the configuration of the main and ancillary equipment. The report presents information on a number of 'cold' experiments carried out using the Stand. In order to check new design approaches, it is planned to arrange in the simulated shielded cell of the Stand the research complex of semi-industrial-scale equipment: the apparatus for pyrochemical reprocessing of spent nuclear fuel (SNF) and the furnace for vitrification of high-level wastes arisen from SNF reprocessing by nonaqueous methods. (authors)

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