Radiochemical Analysis of Spent Nuclear Fuel of VVER-440 Reactor
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ochemical Analysis of Spent Nuclear Fuel of VVER-440 Reactor V. N. Momotova,*, E. A. Erina, A. Yu. Volkova, and V. N. Kupriyanova a
Research Institute of Nuclear Reactors, Dimitrovgrad, 433510 Russia *e-mail: [email protected] Received June 10, 2019; revised June 28, 2019; accepted July 1, 2019
Abstract—The results have been presented of radiochemical analysis of 8 samples of nuclear fuel irradiated in a VVER-440 reactor. The procedures have been described for the radiochemical separation and analysis of nuclides of uranium, plutonium, americium, curium, neodymium, cesium, cerium, samarium, europium, gadolinium, neptunium using radiochemical and instrumental techniques, including ion exchange chromatography, alpha, gamma, and mass spectrometry. The data on isotopic composition, mass content of nuclides, and fuel burnup, calculated by the method of heavy atoms and by accumulation of burnup monitors 145+146Nd, 148Nd, have been reported. Keywords: spent nuclear fuel (SNF), VVER-440, radiochemical analysis, burnup credit, chromatographic separation of elements, isotopic composition, mass content of nuclides, burnup monitor, SNF burnup, mass spectrometry, alpha-, gamma-spectrometry DOI: 10.1134/S1066362220050100
To substantiate nuclear safety during transportation, storage, and reprocessing of spent nuclear fuel, taking into account the actual change in the nuclide composition of the fuel during irradiation, a burnup credit is used [4–9]: an approach that considers the decrease in the reactivity of SNF as a result of changes in the fuel composition during irradiation. Calculations using this approach account for the decrease in fissile materials during irradiation, primarily 235U and 238U, the accumulation of neutron absorbers, for example, 149Sm and 157Gd, and the formation of fissile nuclides, such as 239Pu and 241Pu. To prove the possibility of increasing the density of spent fuel packing taking into account the burnup credit, it is necessary to validate the computation codes [10]. Thepurpose of the work is to obtain an array of experimental data on the isotopic composition, mass content of nuclides, and VVER-440 fuel burnup values required for the subsequent validation of the computation codes.
INTRODUCTION By now, significant volumes of spent nuclear fuel (SNF) have accumulated in the Russian and world nuclear power industry, the efficient handling of which is considered as one of the main directions of increasing nuclear and radiation safety and economic efficiency of nuclear power plants [1, 2]. One of the ways to optimize SNF management is to increase the loading of spent fuel into transport containers, water and dry storage facilitiesIncreasing the capacity of spent nuclear fuel storage facilities due to the denser SNF placement of spent fuel assemblies (SFAs) in them is possible with the unconditional fulfillment of all safety requirements [3]. To substantiate nuclear safety, an approach is used according to which the content of fissile nuclides in spent nuclear fuel is equal to their content in the original unirradia
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