Subjects: Nuclear Science and Technology >> Engineering Technology of Fission Reactor submitted time 2024-04-07
Abstract： Background : For high-fidelity simulations of fluid dynamics in molten salt reactor, even though a supercomputer is able to suppress the period of each simulation, the consequent expense is still prohibitively costly. A possible way to overcome this limitation is the use of Reduced Order Modelling (ROM) techniques. Purpose : Evaluating the accuracy of the ROM methods for reconstructing the velocity and pressure fields. Methods : Two ROM methods based on the Proper Orthogonal Decomposition (POD) with both Galerkin projection, namely FV-ROM (ROM based on Finite Volume approximation ) and SUP-ROM (ROM with supremizer stabilization ), are established for fluid dynamics of molten salt reactor. Then, both methods are tested on the unsteady cases of liquid-fueled molten salt reactor (LFMSR). Results : The FV-ROM demonstrates notable advantages in both velocity prediction and computational efficiency. For laminar and turbulent transient simulations, the average velocity L2 relative errors are less than 0.5% and 0.6%, respectively, with acceleration ratios of approximately 1500 and 1000 times for single time steps. Conversely, the SUP-ROM scheme demonstrates significant prowess in pressure prediction, achieving remarkably low pressure average L2 relative errors of 0.20% and 0.38% for laminar and turbulent transient scenario, respectively. Conclusions : The integration of the SUP-ROM and FV-ROM for fluid dynamics computations of molten salt reactor could significantly enhances computational efficiency and ensure reliability and accuracy of transient simulation.
Subjects: Other Disciplines >> Synthetic discipline submitted time 2023-03-28 Cooperative journals: 《中国科学院院刊》
Abstract： The ocean is essential to country’s strategic interests and common destiny of mankind, and therefore equipment of various kinds is urgently needed for all-around and multi-dimensional ocean observation and exploration. This article brief introduced the two technological approaches of nuclear energy supply for underwater observation and exploration equipment and relevant exchange technologies of nuclear heat to electric power, quantitatively summarized the applicability of nuclear energy supply on all kinds of equipment, discussed the nuclear safety issues thereon, and then recommended that the technology research of radioisotope fabrication and separation and the construction of relevant facility, the development of individual reactor and the construction of relevant common facility, the technology research of thermoelectric conversion, and the research of relevant nuclear safety issues, should be special supported.
Subjects: Nuclear Science and Technology >> Nuclear Science and Technology submitted time 2024-05-12
Abstract： [Background]: The primary heat exchanger (PHX) used in the 10MWt Molten Salt Reactor Experiment (MSRE) at Oak Ridge National Laboratory (ORNL), is a U-tube heat exchanger, where the shell side (hot side) contains the fuel salt from the primary loop, while the tube side (cold side) carries the coolant salt from the secondary loop. [Purpose]: This study aims to deepen the understanding and mastery of the operational characteristics of molten salt heat exchangers, and to accumulate experience in their design and operation within molten salt reactors. [Methods]: the MSRE-PHX is modeled based on the design parameters, theoretical calculations for shell and tube hear exchanger (Kern method and Bell-Delaware method), software simulation (HTRI Xchanger Suite) and computational fluid dynamics (CFD) simulation are performed, critical performance metrics, such as the heat transfer coefficient, the pressure drop, and the heat transfer power, are obtained and compared to the MSRE operation data. [Results]: The findings indicate that the discrepancies from theoretical calculations, HTRI software, and CFD simulations, are all within acceptable margins to the experimental data. Notably, the greatest variance was found with the Kern method, which showed a deviation in heat transfer quantity of about 15%, while the smallest discrepancy was observed in the overall heat transfer coefficient calculated using HTRI software, differing by merely 0.16% from the experimental data; [Conclusions]: All of the methods are suitable and applicable for designing and studying a molten salt shell and tube heat exchanger; moreover, the CFD simulation can provide fine localized details of the heat transfer and flow of the molten salt fluid. This offers substantial theoretical support and practical guidance for the future design and improvement of molten salt heat exchangers.
Subjects: Nuclear Science and Technology >> Nuclear Detection Technology and Nuclear Electronics submitted time 2024-05-11
Abstract： [Background]:In response to the issue of neutron beam instability or misfire during the operation of the Thorium Molten Salt Reactor with a Particle and Neutron Source (TMSR-PNS), it is necessary to design and develop a neutron beam monitor with high counting rate, low neutron beam perturbation, and high neutron/gamma discrimination capability. [Purpose]: This study aims to investigate the influence of structural parameters of neutron beam monitors on their performance. [Methods]: Firstly, considering that the energy spectrum of TMSR-PNS mainly focuses on the energy range from thermal neutrons to 1 MeV, LiF was chosen as the neutron conversion material. The SRIM program was used to calculate the range of secondary charged particles in the neutron conversion layer and the scintillator, providing a preliminary reference for determining the thickness. Subsequently, a relevant physical model was established using Geant4, irradiating with neutrons and gamma rays of different energies. Finally, the simulation results were used to determine the effects of parameters such as neutron conversion layer thickness, scintillator thickness, metal shell, and the placement angle of the PMT on the detector performance. [Results]: The neutron conversion layer thickness of the scintillator is relatively suitable at about 2 µm for intrinsic detection efficiency. With a scintillator thickness of 2 mm and a discrimination threshold of 0.1 MeV, the detector demonstrates insensitivity to gamma rays. Additionally, by comparing the impact of different shell materials on electron generation by gamma rays, iron, which produces fewer electrons, was selected as the shell material. [Conclusions]: The influence of detector structural parameters on detector performance obtained in this study is of guiding significance, providing theoretical reference for the subsequent preparation of detectors.
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