Subjects: Nuclear Science and Technology >> Nuclear Science and Technology submitted time 2024-07-12
Abstract： [Background] The imperative need for high-performance propulsion systems in deep space exploration missions has led to a focus on improving the design of nuclear thermal propulsion reactors (NTPRs). The existing methods for designing NTPRs have been identified as lacking in systematic and integral approaches. [Purpose] The purpose of this study is to propose a novel multi-objective optimization design method for NTPRs to achieve a core design that offers high thrust, high specific impulse, extended service life, and reduced weight. [Methods] The methodology involves several key steps: Constructing a heat transfer model between assemblies based on their thermal interaction characteristics. Integrating this model with the flight performance model of the nuclear rocket and the two-dimensional criticality model of the assemblies. Proposing a multi-objective parameter screening method that combines the aforementioned models for coupled iterative calculations to optimize the core layout. Ensuring that the design meets comprehensive standards in thermal engineering, flight performance, and neutron physics while minimizing the core mass. Utilizing the open-source Monte Carlo software OpenMC to perform detailed three-dimensional neutronics calculations and conduct a comprehensive assessment of the reactor's criticality, safety, and burnup performance. [Results] The study's findings demonstrate that the low-enriched uranium (LEU) NTPR conceptual design, developed using the proposed method, has preliminarily satisfied the design criteria for high thrust, high specific impulse, long service life, and lightweight. [Conclusions] The results suggest that the proposed method for NTPR core design is effective in meeting the demanding requirements of future manned deep space exploration missions, offering a promising direction for further research and development in this field.
Subjects: Nuclear Science and Technology >> Nuclear Science and Technology submitted time 2024-06-20
Abstract： [Background]: The single-phase reversed flow in inverted U-tubes of steam generator (SG) leads to increasing flow resistance and decreasing heat transfer area, so it is meaningful to study this phenomenon. [Purpose]: The water level of the secondary side in SG can influence the single-phase reversed flow, it is necessary to clarify its influence mechanism from a more general viewpoint. [Methods]: The dimensionless conservation equations were derived first, and the extreme point was obtained based on the equations. Then the effect of the water level of the secondary side under conditions of different lengths, dimensionless resistance number, and dimensionless heat transfer number was analyzed. [Results]: The decrease in the water level leads to the critical point of the single-phase reversed flow gradually approaching the origin, the influence law of the water level is the same under different pipe length conditions. As the water level decreases, the influence of the dimensionless resistance number and dimensionless heat transfer number on the critical point gradually reduces. [Conclusions]: This study theoretically proves that the effect of secondary water level on single-phase reversed flow is not conducive to the occurrence of backflow, and explains the reasons from a mechanistic perspective, which can assist in accident analysis of related nuclear power plants.
Subjects: Nuclear Science and Technology >> Nuclear Science and Technology submitted time 2024-05-30
Abstract： [Background]: The single-phase reversed flow in inverted U-tubes of steam generator (SG) leads to increasing flow resistance and decreasing heat transfer area, so it is meaningful to study this phenomenon. [Purpose]: The water level of the secondary side in SG can influence the single-phase reversed flow, it is necessary to clarify its influence mechanism from a more general viewpoint. [Methods]: The dimensionless conservation equations were derived first, and the extreme point was obtained based on the equations. Then the effect of the water level of the secondary side under conditions of different lengths, dimensionless resistance number, and dimensionless heat transfer number was analyzed. [Results]: The decrease in the water level leads to the critical point of the single-phase reversed flow gradually approaching the origin, the influence law of the water level is the same under different pipe length conditions. As the water level decreases, the influence of the dimensionless resistance number and dimensionless heat transfer number on the critical point gradually reduces. [Conclusions]: This study theoretically proves that the effect of secondary water level on single-phase reversed flow is not conducive to the occurrence of backflow, and explains the reasons from a mechanistic perspective, which can assist in accident analysis of related nuclear power plants.
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