Experimental research of the neutron-shielding performance of several shielding materials
[Objective]The rapid development of nuclear technology and the continuous expansion of nuclear energy applications have focused engineering research on the conceptual design and shielding calculations of advanced reactors.The development of third-generation advanced modular small reactors has elevated the requirements for the types of neutron-shielding materials,equipment quality,and compactness of design.For shielding,these materials must exhibit good neutron and γ-ray slowing down and absorption performance and have excellent mechanical properties to ensure structural integrity during long-term operation.Traditional shielding materials mostly rely on simple high-hydrogen-content compounds,high-density metal,and boron-containing concrete materials.However,when shielding small solid-state reactors,they gradually exhibit shortcomings in physical and mechanical performances.Addressing the inadequacies in the design and application research of composite shielding solutions for current small solid-state reactors,lightweight materials with excellent composite shielding performance can effectively meet the radiation shielding needs in complex geometric structures and operational scenarios.[Methods]This study selected lightweight materials with excellent performance for a single-tube neutron radiation detection system and conducted relevant performance experiments.Theoretical values and experimental results were cross validated through uncertainty simulations.After a comprehensive comparison of the physical performances and processing costs of neutron slowing down and absorption materials,coupled with discussions on the feasibility of neutron-shielding experiments in an experimental environment,boron carbide,titanium hydride,and zirconium hydride were chosen as the shielding materials for this experiment.Special-sized containers were customized,and samples encapsulated in organic glass and PVC materials were prepared.Performance tests of the shielding materials were conducted by counting the number of neutrons at counter positions in the single-tube neutron radiation detection system.The experimental data,including counting averages(n/s),sample variance,and the characterized shielding effectiveness,were recorded,summarized,and analyzed in detail.Subsequently,the detection system was modeled using the independently developed reactor Monte Carlo code by the REAL team at Tsinghua University.Monte Carlo particle transport simulations were used to validate the consistency between experimental and theoretical data.[Results]The experimental results indicate the following findings:1)The shielding enclosure device comprising PVC material has virtually no impact on background neutron counts,while the use of organic glass material leads to a substantial effect,reaching 5%-6%.2)Under the experimental conditions,boron carbide exhibits a noticeable absorption effect on neutrons,with a 3 mm thickness already achieving a considerable absorption effect at nearly an order of magnitude.3)Under equivalent experimental conditions,the shielding effectiveness of titanium hydride and zirconium hydride is unsubstantial.However,titanium hydride slightly outperforms zirconium hydride.This superiority is observed because,in hydrogen-containing materials,titanium hydride and zirconium hydride have the same proportion of hydrogen nuclei.Because of the slightly higher neutron absorption cross-section of titanium nuclei compared to zirconium nuclei,the absorption effect makes titanium hydride slightly better than zirconium hydride in overall shielding effectiveness.4)The experimental data collected align well with Monte Carlo simulation calculations,indicating the correctness of the experimental approach in this study.[Conclusions]The data and conclusions obtained from this study on lightweight shielding materials with specific characteristics apply to other novel shielding systems and devices.The research indicates that under equivalent irradiation conditions,shielding effectiveness increases in the order of boron carbide,titanium hydride,and zirconium hydride.Simulations and experiments provide guidance and validation,establishing a solid theoretical foundation for introducing composite diffusive shielding materials into portable small nuclear power systems.
Neutronshielding materialMonte Carlo simulationsingle-tube neutron ray detection
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