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Abstract: Features and capabilities of the SUN BPSD module for assessing the error in fuel burnup calculations due to the uncertainty of nuclear data and reactor plant process parameters, as well as fuel irradiation conditions, are described. Using the SUN module, two different methods for estimating the uncertainty of irradiated fuel characteristics were implemented. The post-reactor studies of fuel rods irradiated in a BN-350 reactor with mixed uranium-plutonium oxide fuel were considered as a demonstration calculation test using the SUN module. PubDate: 2023-10-20
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Abstract: The article considers EP823 12% Cr ferrite-martensite steel, selected in terms of the material for fuel rod claddings, as well as the control and protection elements of BREST OD-300 and SVBR-100 reactors. Based on the analysis of the published results of non-isothermal circulation facility tests, a comparison of EP823 steel corrosion rates in a liquid lead and lead-bismuth eutectic system demonstrated their proximity. PubDate: 2023-10-20
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Abstract: One of the limiting factors of the service life of a nuclear power plant involves the state of the reactor vessel and its internals. The structural materials of the vessel and its internals are subjected to intense irradiation and thermomechanical loads, resulting in radiation embrittlement that affects the mechanical properties of these elements. For this reason, determination of the radiation load, including fast neutron fluence, damaging dose (displacement per atom), and power density, represents an urgent task. In order to confirm the determination reliability of these values, the sensitivity of the calculated results to the uncertainty of the initial data used in the calculation was analyzed. The present paper considers uncertainties due to technological deviations in the dimensions of the core elements, geometric dimensions, operational parameters, and mass of the fuel in the fuel assembly. The effect of these uncertainties is estimated for the displacement per atom and power density of VVER-1000 internals. PubDate: 2023-10-20
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Abstract: For the possible operation of power units with the RBMK-1000 reactor during the period of the formation of a graphite stack, NIKIET performed a series of experiments to recreate the force action of the graphite stack on the sealed vessel of the reactor, represented by the KZh metal structure. The experiments justified the joint movement of the graphite stack and 50 mm metal structure with the assumption of up to 5% local plastic deformations of the metal structure at the contact with the graphite stack, which was beyond the limits of the strength calculations valid at the time of works. As a part of the performed study, the behavior of graphite blocks during their destruction under interaction with the metal barrier was determined. The experiments, which revealed the significant conservatism of previous calculations, showed that graphite blocks can be destroyed under interaction with the metal structure without damaging the safety barrier. PubDate: 2023-10-20
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Abstract: The main parameter for assessing the status of the transport NPP core consists of the total specific activity of iodine in the primary coolant samples 2 h after the sampling. The article analyzes the variations in this parameter of the primary coolant used at the KLT-40S transport nuclear power plant. When taken in the modes of the radiation and technological control, the total specific activity of iodine isotopes in the coolant samples can differ by almost 2 times at the same status of the core. Fluctuations in the values of the parameter are determined by the variations in the activity of 132I. When selecting the parameters for assessing the status of the core, it is advisable to use the activity of 131I, 133I, 134I, 135I, or their total activity with the exclusion of 132I. During the determination of total activity by the radiometric method, iodine isotopes should either be isolated on the silver-impregnated membrane from the gas phase to remove interfering radionuclides from the load, or an additional measurement of the prepared sample activity should be performed 24 h after the sampling. PubDate: 2023-10-20
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Abstract: The paper sets out the results of a study into the characteristics of tritium diffusion in the structural material of a liquid-salt reactor as represented by KhN80MTYu alloy. The studies were carried out using membrane and radioluminographic methods in the temperature range of 450–750°C. NP2 grade nickel was used as a reference material. KhN80MTYu alloy was established to have the significantly lower characteristics of the tritium diffusion as opposed to the pure nickel of the NP2 grade with no kinks in temperature dependencies. An exposure in the melt of ammonium bifluoride was established to increase the diffusion coefficient of tritium. This may mean that the action of the fuel salt melt on the wall during the reactor operation may accelerate the tritium diffusion. PubDate: 2023-10-20
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Abstract: The paper analyzes the effect of tectonic activity on the safety of the geological repository at the Yeniseisky radioactive waste (RW) repository (Nizhnekansky massif, Krasnoyarsk Krai) in the event of the formation of faults in the host rocks following the loading of wastes into the repository. A 3D model of the radioactive contamination transfer from the repository by groundwater is considered, taking into account the inhomogeneous permeability of rocks. The orientation and location of the faults are set based on the modeled stress-strain state of the rocks in this area, as well as data obtained from field and spatial surveys on contemporary tectonic activity in the considered area. Submeridional faults were demonstrated to have no significant effect on the spread rate of the radioactive contamination. However, the activation of the most probable latitudinal fault may lead to the rapid movement of contaminated groundwater in the fault zone towards the Yenisei. The efficacy of plugging various areas in the sublatitudinal fault zone to reduce the migration rate of contaminating radionuclides is considered. PubDate: 2023-10-20
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Abstract: The results of calculating the βeff effective fraction of delayed neutrons and the Λ lifetime of prompt neutrons, both when taking into account and excluding the value function, are presented. The analysis, concerning the effects of accounting for the neutron value function at various degrees of its expansion, as well as depending on the physical and geometric parameters of the system, is conducted. The calculations were performed for twelve experiments from the ICSBEP collection. The analysis of the results states the necessity of accounting for the value function in small systems with a reflector and a large number of neutrons. No accounting for the value function is required for estimating the kinetic functionals in systems that are close to infinite. PubDate: 2023-10-20
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Abstract: The paper considers features of enriched regenerated uranium hexafluoride purification from 232, 234, 236U in a double cascade with a supply of uranium hexafluoride wastes for the additional feeding of the first cascade. The effective purification from 236U is carried out in the first cascade at a 235U concentration of less than 20% in long cascades with a large number of stages. The parameters of the second cascade, fed by the product of the first one, which significantly reduce the concentration of 232, 234U in the wastes, were determined. Its reduction with uranium hexafluoride wastes ensures the compliance with the requirements of the ASTM C996-20 specification, established for enriched industrial uranium hexafluoride. PubDate: 2023-10-20
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Abstract: The present paper considers the physicochemical properties of valence electrons in the LiF–NaF–KF system within the framework of energy band theory. Here, the movement of the Fermi level in its band gap is equivalent to variations in the redox potential of the salt. When used to determine the limit level of the triple eutectic deoxidation, the electrochemical window identifi ed in the band gap may be suffi cient to suppress its corrosion activity in the liquid-salt reactor. However, this assumption, as well as the natural maintenance of this level in a mixture of three eutectic systems (LiF)0.99Li0.01, (NaF)0.97Na0.03, (KF)0.95K0.05, taken in the ratio of components (LiF)0.465(NaF)0.115(KF)0.42, requires experimental verification. PubDate: 2023-10-20
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Abstract: The paper describes the design and the process mode of an M-1281 sorption unit for the extraction of uranium hexafluoride and hydrogen fluoride from gases based on chlorine trifluoride or fluorine using the fluorides of lithium and sodium. The extraction of uranium hexafluoride by sodium fluoride yields over 99.8%. Hydrogen fluoride in combination with lithium and sodium fluorides is extracted at 95.6%. In this case, the content of uranium hexafluoride and hydrogen fluoride in the gas after the M-1281 unit does not exceed 0.02 and 1 vol%, respectively. According to the obtained results, about 14 tonnes [metric tons] of uranium hexafluoride, variously enriched in 235U, can be additionally directed to the main process of the plant, while more than 1 tonnes of anhydrous hydrogen fluoride can be supplied to the production of elemental fluorine. PubDate: 2023-10-20
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Abstract: One of the relevant factors when increasing the competitiveness of water-cooled reactors is the introduction of accident-tolerant fuel to significantly reduce economic risks during NPP operation. The present study aims to develop a methodology for assessing the impact of this fuel on NPP competitiveness criteria. The main attention is paid to the assessment of the maximum permissible increase in production costs – the manufacture of fuel assemblies, ensuring the preservation or reduction of the fuel component in the cost of NPP electricity. A new condition for the competitiveness of accident-tolerant fuel, indicating the possibility of increasing the costs of its production by a half compared to the conventional fuel, was formulated. PubDate: 2023-10-20
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Abstract: The paper considers and compares methods for obtaining spectra of fast neutrons using detectors based on a diamond sensor, an organic (plastic) scintillator for separating neutrons and γ-quants, and a spectrometric set of threshold activation detectors. The neutron spectrum was unfolded using the methods of least squares, Tikhonov regularization, neural networks, and maximum entropy, implemented in the MAXED code, as well as the GRAVEL iterative algorithm. In order to form detector response matrices, mathematical simulation methods and analytical calculations were used followed by verification using experimental data. The unfolding quality criteria, according to which the best method is selected, are given. PubDate: 2023-10-20
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Abstract: The article considers the possibility of producing isotopes at nuclear power plants with RBMK-1000 reactors. In particular, the specialists of NIKIET developed technical documentation for substantiating the production and expanding the range of medical isotopes at the Phase 2 power units of the Leningrad NPP. The combination of design works and calculation justification demonstrated the possibility of the safe conversion and operation of two standard channels in the RBMK-1000 control and protection system of the Leningrad NPP power units 3 and 4 for irradiating starting substances with thermal neutrons and producing 131I, 153Sm, and 177Lu. By expanding the production of medical isotopes at the Leningrad NPP, as well as at other RBMK-1000 nuclear power plants in the future, current radioisotope demand from the pharmaceutical industry can be met at the same time as enlarging the number of available preparations. PubDate: 2023-10-20
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Abstract: The article considers the specifics of innovative nuclear power facilities from the perspective of cost estimation. Approaches to cost estimation, which aim to ensure the greatest reliability and provide for composing detailed calculations and using analogs, were identified taking into account the initial data available at the pre-design stage. An attention is focused on the importance of competitiveness analysis that takes into account the life cycle of the facility. The scientific novelty of the study lies in the presented approaches for assessing the cost of constructing innovative facilities in conjunction with the various stages of pre-design works, including conceptual design and feasibility study, which are implemented in the practical activities of the Proryv project stream. PubDate: 2023-10-20
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Abstract: By reducing the consumption of hydrocarbons for the production of thermal and electric energy, problems associated with global heating can be mitigated. Industrial, transport, and utility sectors currently account for about 70% of total consumption of fossil energy resources. In order to significantly reduce carbon emissions, it will be necessary to replace the energy of burning fossil fuels with nuclear and renewable energy sources. In addition, nuclear energy can act as a large stabilizing energy source for the production of hydrogen for use in industry, transport, and distributed energy engineering, as well as in the production of high-temperature heat for energy-intensive technological processes. In terms of financial return, the production of energy carriers (hydrogen, methanol, etc.) using atomic energy is equivalent to the production of energy carriers in the electric power industry. The Rosatom State Corporation has presented a program for the development of atomic-hydrogen energy engineering and already begun its implementation. PubDate: 2023-10-18
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Abstract: The Fermi level in uranium dioxide with band gap εg = 2.1 eV is a logarithmic identifier of the oxidation state of the dioxide and serves as a measure of the electron occupation of the local energy levels in the band gap. An impurity additive in the form of a trivalent metal is required in order to transfer the dioxide into a stable hypostoichiometric state with a high density of oxygen vacancies. This can be accomplished in mixed uranium-plutonium fuel, which is then easily compacted with dispersed particles of uranium carbide. PubDate: 2023-09-09 DOI: 10.1007/s10512-023-00995-4
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Abstract: Given the obligation to safely navigate a full de-energization condition of NPP it is important to study the natural circulation of the coolant in the primary loop of NPP with water-moderated/cooled [pressurized-water] reactors in the event of de-energization of the main circulation pump. At Balakovo NPP No. 3 with 104% load, the power unit underwent complete de-energized along with the main circulation pumps. When switching to natural circulation of the coolant, the temperature in the hot legs dropped from 320 to 300°C. This attests reliable and stable cooling of the core in the condition of natural circulation. A coefficient is proposed for assessing the level of natural circulation. It can be used to determine the flow rate of the circulating coolant on full de-energization of the main circulation pumps. Based on the measurements of the standard information- computational system of a power unit, the residual power release and the coefficient of natural circulation were determined in the entire area of work with the main circulation pumps de-energized for 45 min. PubDate: 2023-09-09 DOI: 10.1007/s10512-023-00994-5
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Abstract: The means for measuring the volumetric activity of radioactive noble gases, aerosols, and radioiodine were developed in line with the current requirements of the designed nuclear energy facilities. This article presents aspects of equipment design and the metrological characteristics of technical means and indicates directions for further research aimed at increasing reliability in assessing emissions from nuclear facilities. PubDate: 2023-09-08 DOI: 10.1007/s10512-023-00999-0
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Abstract: Low-concentration nuclides – impurity nuclides – are increasingly in demand in radiochemistry for defining more precisely the neutronic characteristics of the medium. On use in precision calculations, impurity nuclides afford more accurate calculations. This article considers aspects of the calculation of one-group cross sections of the high-threshold reactions (n, nt), (n, 2α), (n, 2p), (n, pα), (n, nd), (n, np), (n, 2nα), and others in extended libraries and their influence on the nuclide composition of irradiated compositions in calculations using the MZK precision program. This program affords guaranteed accuracy of calculated nuclides, including impurities. A procedure is proposed for calculating one-group cross sections as applied to the spectrum in fast reactors. PubDate: 2023-09-08 DOI: 10.1007/s10512-023-01001-7
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