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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