The results of investigations of the leading operation of a nonaqueous technology for reprocessing fuel elements from nuclear reactors -dissolution of fuel claddings in a zinc-based melt -are presented. Data obtained in experiments on simulators and samples of irradiated fuel elements in standard BOR-60 and SM-2 packages with different burnup and holding time are presented. In the experiments, the metallic melt was separated from the fuel by filtering through a mesh and regenerated by vacuum distillation for reuse. The uranium and plutonium extraction was 99.99%. The behavior of individual radionuclides is described.The growth of energy consumption is accompanied by increasing attention to the ecological consequences of the use of the conventional forms of primary sources of energy (coal, gas, oil, water). The natural reserves of these resources are decreasing appreciably. Under the circumstances, nuclear power should play a larger role. The nuclear component in the energy balance now comprises about 10% of the consumption of all world primary sources of energy, which is accompanied by the accumulation of spent nuclear fuel. According to IAEA estimates, about 200,000 tons of nuclear fuel was loaded into reactors in all nuclear power plants in the world, and every year this figure increases by 10000-12000 tons, Russia contributing approximately 800 tons [1].Spent nuclear fuel is processed at plants after a long holding time in storage sites to decrease the intensity of the radiation from radionuclides that negatively influence the chemical stability of reagents as structural materials. Prolonged storage (cooling) makes a substantial contribution to the cost of the fuel cycle. This is why it is urgent to develop a nonaqueous technology for reprocessing spent fuel which has not cooled down much. Nonaqueous methods are considered to be the most promising, first and foremost, for reprocessing spent nuclear fuel with a short holding time.One direction of nonaqueous methods for reprocessing spent fuel elements is combining the operations of decladding by dissolution in metallic melts with further processing of the fuel by an oxidative-alkaline melt to remove uranium and plutonium from the main mass of the fission products and transferring uranium and plutonium into oxides (with or without extraction conversion) in order to fabricate secondary nuclear fuel. The development of this avenue began at the All-Union Scientific-Research Institute of Chemical Engineering at the end of the 1970s -investigations were performed using simulators and segments of irradiated fuel elements from BOR-60 and SM-2 reactors with different degrees of burnup of heavy atoms and cooldown during the period of the experiment [2].Dissolution of Cladding. Analysis and an experimental check showed that the fuel-element cladding material selectively dissolves in a metallic melt consisting of zinc (base) and 3-5 mass% antimony without touching the fuel (Table 1). The viscosity of the melt increases as the concentration of the cladding material increase...

The results of investigations of the preliminary removal of the products of radioactive decomposition from irradiated nuclear fuel to obtain uranium and plutonium which are suitable for reuse in fuel fabrication are presented. Nitrate-alkali melts are used for the operation. The experiments are performed on simulators and irradiated samples of BOR-60 fuel in remote-controlled hot boxes. The coefficients of removal of fission products are presented. A technological scheme, which will shorten the fuel cycle, for purifying hot nuclear fuel is recommended.In the present paper, a method of preliminary removal of most of the fission products from decladded spent fuel is described. The fuel is processed with an alkaline-nitrate melt, the compounds formed are dissolved, and uranium and plutonium are converted into oxides for preparing secondary nuclear fuel.Preliminary Purification of Irradiated Fuel. The problem of reprocessing spent fuel from fuel elements involves not only safe storage but also the need to accelerate the recycling of the fissioning materials -235 U and 239 Pu -into the nuclear-fuel cycle. In turn, the reprocessing of high-level fuel engenders difficulties of a technical character, specifically, ensuring critical safety with respect to the mass of the 235 U and 239 Pu isotopes, choosing materials which are resistant to the radiation from the reagents and corrosion-resistant, and removing and storing radioactive wastes.Fission products are present in a fuel element in different aggregate states: gaseous form and condensed phase. Tritium, krypton, xenon, and iodine are present in the gas phase. The flow of the gaseous fission products into the free space in a fuel element depends on the degree of burnup of the fuel. Most of the fission products are in the form of oxides which are produced as a result of the reaction of isotopes with oxygen. Some of the elements (Ru, Mo, Tc, Rh, and Pd) form metallic inclusions. A calculation has shown that when the irradiated fuel is allowed to stand for a one to three months 95 Zr + 95 Nb, 103,106 (Ru + Rh), 89 Sr, 91 Y, 141,144 Ce, and 144 Pr make the main contribution to its radioactivity.The nonaqueous methods developed for reprocessing spent fuel (fluoride, molybdate, in melts of metals and chlorides, electrochemical, and others) make it possible to remove the fission products from the fuel. However, the need to use high-temperature processes and the lack of inexpensive technological structural materials for building the equipment are holding back their adoption at the present time. In this connection, schemes where pyrochemical operations are used for separating fuel which is still hot from the cladding and most of the fission products are of great interest; the final removal of uranium and plutonium can be performed by liquid extraction methods which have been developed.Comparing existing methods of preliminary removal of fission products from fuel has led to the conclusion that methods using oxidative-alkaline and, specifically, nitrate-alkaline melts best meet t...