One scenario for using excess Russian weapons plutonium is to load it into VVÉR-1000 reactors. It is proposed that up to 40% of the fuel assemblies with uranium fuel be replaced with structurally similar fuel assemblies with mixed uranium-plutonium fuel. The stationary regime for burning fuel has the following characteristics: the run time is about 300 or 450 eff. days, the yearly plutonium consumption reaches 450 kg, the neutron-physical characteristics are close to the corresponding regimes with uranium fuel. The nuclear safety criteria and the irradiation dose for workers handling fresh and spent mixed fuel remain within the limits of the normative values. The use of mixed fuel makes it necessary to upgrade certain systems at nuclear power plants. A substantial quantity of weapons plutonium can be loaded every year into VVÉR-1000 reactors, effectively using the energy potential of this plutonium.One currently considered scenario [1] envisions using excess weapons plutonium in mixed uranium-plutonium fuel for VVÉR-1000 reactors. When such fuel is adopted in operating power generating units, the following conditions must be satisfied:• adoption of the fuel should not decrease the production of electricity or lower the uranium fuel utilization efficiency; • the energy potential of weapons plutonium should be used effectively for electricity production;• the isotopic composition of the removed plutonium should be close to that of power plutonium. This article summarizes the results of investigations performed over the last five years [2][3][4][5]. The neutron-physical characteristics of a VVÉR-1000 core with a partial load of mixed uranium-plutonium fuel, the salient features of the irradiation of three experimental fuel assemblies, licensing of computational programs, the nuclear and radiation safety when handling such fuel, the required upgrading of the systems of a nuclear power plant, and other aspects are discussed.The results presented below were obtained within the framework of Russian-American and Russian-French intergovernmental agreements concerning the salvaging of weapons plutonium. Specialists from the Physics and Power Engineering Institute, OKB Gidropress, All-Russia Research Institute for Standardization in Machine Engineering, and the All-Russia Research Institute of Nuclear Power Plants participated at different stages of this work. A substantial fraction of the neutron-physical and thermohydraulic calculations was repeated using domestic computational tools or analyzed by specialists at Oak Ridge National Laboratory (USA), the Atomic Energy Commission and the firm Framatom (France), and previously the Society for Safety of Systems and Reactors, the Siemens Company (Germany).Characteristics of Mixed Uranium-Plutonium Fuel. Fuel made of weapons quality plutonium is expected to be fabricated according to the European technology MIMAS [6], based on mixing UO 2 and PuO 2 powders. Depleted uranium contains 0.1-0.2 mass% 235 U. The following isotopic composition of plutonium was assumed for computation...

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