Journal Issue: Nuclear Energy and Technology
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Volume
10
Number
1
Issue Date
Journal Title
Journal ISSN
2452-3038
Том журнала
Том журнала
Статьи
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A brief investigation of the dose field virtual simulation tools for reactor decommissioning and preliminary design for the HWRR reactor in China
(2024) Guo, Y.; Nie, P,; Li, R.; Zhang, L.; Zhang, X.; Ren, R.; Zhao, Z.
The calculation and visualization of the dose field in the decommissioning of nuclear facilities is one of the important functions of the decommissioning virtual simulation system. The dose field simulation tools can provide radiation field distribution and play an important role in determining the decommissioning plan and protecting personnel during the engineering implementation process. This article investigates the development of dose field calculation and visualization in the reactor decommissioning virtual simulation systems. A preliminary technology plan suitable for the development of the decommissioning dose field calculation and visualization display programs of the first Heavy Water Research Reactor (HWRR) in China is proposed. The applicability of the selected scheme is analyzed. The functional requirement and development direction of the HWRR reactor decommissioning dose field tool are preliminarily determined. Furthermore, the reactor vessel of HWRR reactor is modeled, the dose field distribution is calculated and visualized based on the preliminary decommissioning code. This research can provide technical support for the development of the decommissioning simulation system for the first HWRR reactor in China.
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Experience in the production of 99Mo from low enriched uranium at the VVR-ts research nuclear facility
(2024) Kochnov, O. Y.; Stepanov, V. I.; Pakholik, D. A.; Kolesov, V. V.; Nikulin, E. V.
The key industrial method for producing 99Mo is production of the radionuclide as one of the 235U fission fragments. 235U is irradiated with neutrons in a nuclear reactor (both heterogeneous and homogeneous nuclear reactors can be used) and then processed in radiochemical laboratories, where 99Mo is chemically extracted from fission products. Both highly enriched uranium (HEU) and low enriched uranium (LEU) can be used to produce 99Mo by the fragmentation method. To date, almost all world producers, with the exception of Russia, are either in the final stages of transferring production from highly enriched uranium to low enriched uranium, or are already producing 99Mo using LEU. This is due to the problems of non-proliferation of nuclear materials and the prevention of the likelihood of terrorist threats. A number of experimental studies have been carried out on the basis of the VVR-ts research reactor. Experimental studies included the study of the effect of LEU targets on the reactivity reserve of the VVR-ts reactor, irradiation of these targets in experimental channels and separation of 99Mo from them. The paper presents the results of producing and separating 99Mo from targets with LEU material. It is shown that it is necessary to improve the processing technology to increase the production of fragmented 99Mo from LEU.
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Computational simulation of the heat and mass transfer processes occurring in the containment of Novovoronezh NPP II’s units 1 and 2
(2024) Soloviev, S. L.; Shishov, A. V.; Povarov, V. P.; Yaurov, S. V.
The paper presents information on the key approaches to the design of the containment ventilation system for units 1 and 2 of Novovoronezh NPP II (NPP-2006 project). The authors have developed a CFD model for the containment of Novovoronezh NPP II’s units 1 and 2, which includes the key structural components and the basic equipment installed within the containment. A series of the containment air temperature measurements was undertaken during power operation of the units. Based on the measured temperature values, a series of calculations was undertaken to determine the air temperature field inside the containment. It is revealed that when ensuring the design characteristics of the cooling capacity of the ventilation system stages, the design parameters of the containment air, wall and equipment temperature are achieved. In addition, with proper mixing of the containment air, it is possible to significantly reduce the average air temperature in the most “hot” rooms. Based on the calculation results, causes have been identified for the low efficiency of the ventilation system, and specific measures have been proposed for increasing significantly the system capacity. The proposed approach to determining the characteristics of ventilation systems using modern methods of three-dimensional computational hydro-gas dynamics makes it possible to optimize and modernize existing ventilation systems, as well as to assess the efficiency of ventilation at the design stage of nuclear power plants. The developed and proposed CFD model makes it possible to do this at the modern level without resorting to bench/experimental modeling issues.
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Numerical simulation of fluid dynamics and mixing in headers of sodium-air heat exchangers
(2024) Smetanin, T. R.; Pakholkov, V. V.; Rogozhkin, S. A.; Shepelev, S. F.; Рогожкин, Сергей Васильевич
The paper presents the results of a numerical simulation for sodium fluid dynamics and mixing in the tubing system of an air-cooled heat exchanger (AHX), which is a part of the emergency cooldown system (ECS) of sodium fast reactors (SFRs). Non-uniform sodium flows in the AHX tubing system may lead to the mixing of different-temperature sodium flows, temperature fluctuations and tube breaks. It was found in the course of investigating accidents involving breaks in the PFR and Phénix reactor AHX tubing systems that the failure was caused by the metal temperature fluctuations (Cruickshank and Judd 2005).
The numerical simulation used three- and one-dimensional computer codes. It has been found that the calculations of the AHX sodium flow rate distribution with a practically acceptable accuracy can be performed using a one-dimensional code. The factors that influence the non-uniform distribution of sodium flows in the AHX tubing system have been analyzed. Calculations have been performed for the AHX sodium flow distributions and for the mixing of different-temperature sodium flows in the AHX outlet header. The results are presented from calculating the amplitude of sodium fluctuations near the AHX header walls. The effect from shutting down several modules on the non-uniform flow distribution and temperature fluctuations in the AHX has been investigated. Approximations of numerical solutions have been obtained for the sodium flow distribution as a function of the number of the modules shut down.
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Towards a uniform description of recombiners performance by a consistent CFD approach with the use of a detailed mechanism of hydrogen oxidation
(2024) Avdeenkov, A. V.; Achakovskii, O. I.; Ketlerov, V. V.; Soloviev, S. L.; Duong, Q. H.
For a consistent CFD substantiation of the recombiner performance, a detailed mechanism of hydrogen and oxygen recombination is used. The detailed mechanism of chemical kinetics (multi-step recombination reaction) makes it possible to claim universality, both in the numerical justification of the recombiner performance and in the justification of the flameless recombination threshold and makes it possible to justify the method for optimizing the recombiner to improve its characteristics. The models developed based on this approach were applied to both flat and cylindrical catalytic elements, which are used in FR and RVK recombiners, respectively. As part of the numerical studies, the detailed recombination mechanism was verified, namely the temperature distribution along the catalytic elements was compared and the performance of catalytic elements was compared as well. Good agreement was obtained between the calculated and experimental data. The approach considers not only the mechanism of surface recombination of hydrogen and oxygen on platinum, but also the mechanism of recombination in the gas phase. This makes it possible to calculate the onset of intense combustion outside the catalytic plates, which is a sign of volumetric ignition of the hydrogen-air environment. The concentrations at which such ignition is possible were obtained at different contents of water vapor in the medium. Thus, the proposed approach and the created models make it possible to fully describe the performance of recombiners of distinct designs without the use of additional experimental data, which is extremely necessary when justifying the hydrogen explosion safety of nuclear power plants.