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NUCLEAR TECHNIQUE

 

 

 

 

 

 

 

 

 

 

 

 
  • Editor-in-Chief: MA Yugang
  • ISSN:0253-3219
  • CN:31-1342/TL
  • Supervisor: Chinese Academy of Sciences
  • Sponsor: Shanghai Institute
    of Applied Physics,Chinese Academy of Sciences; Chinese Nuclear Society

 

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Simulation and life evaluation of creep crack propagation in GH3535 alloy based on fracture mechanics

BackgroundThe life assessment of high-temperature components with defects in the thorium molten salt reactor (TMSR), which is one of the fourth-generation reactors, is a crucial part of structural integrity assessment.PurposeThis study aims to simulate the creep crack propagation CCP of compact tensile (C(T)) specimens and to carry out a life assessment of these specimens, providing engineering guidance for life prediction of defect structures at elevated temperatures in Thorium Molten Salt Reactor (TMSR).MethodsThe CCP of C(T) specimens was firstly simulated by using the Contour integral evaluation method in finite element analysis (FEA) software Abaqus. Subsequently, based on time-dependent creep fracture mechanics, an automated analysis program was written in Python to calculate the creep fracture parameter C*. Then, a time-dependent failure assessment diagram (TDFAD) for GH3535 alloy was established, and the stress intensity factor K and reference stress σref were extracted and calculated from FEA results. Finally, a life assessment of C(T) specimens was carried out.ResultsThe comparison between experimental data and simulation results by using the creep fracture parameter C* demonstrates that the FEA method can effectively simulate the crack propagation in the specimens. The TDFAD of GH3535, combined with FEA, visually presents the process of crack propagation leading up to equipment failure.ConclusionsResults of this study explain the behavior of GH3535 alloy's creep cracks and provide engineering guidance for life prediction of defect structures at elevated temperatures in TMSR, ensuring the safety and reliability of the reactor's high-temperature components. The life assessment of high-temperature components with defects in the TMSR is a crucial part of structural integrity assessment.

> Special Topic of the 22nd National Conference on Structural Mechanics in Reactor Technology

WANG Wen, WANG Xiaoyan, LI Zhijun

Simulation and life evaluation of creep crack propagation in GH3535 alloy based on fracture mechanics
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Volume 49 期 7，2026 2026年第49卷第7期

  • Special Issue of Excellent Papers on The Second Academic Annual Conference of the Research Reactor and Innovative Reactor Association of Chinese Nuclear Society

    WU Hao, GUI Nan, YANG Xingtuan, TU Jiyuan, JIANG Shengyao

    DOI：10.3724/j.0253-3219.2026.hjs.49.250435
    摘要：BackgroundHigh-temperature gas-cooled reactors (HTGRs) are advanced Generation IV nuclear systems, in which radiation-dominated heat transfer within the pebble bed plays an important role in core thermal-hydraulic behavior.PurposeThis study aims to develop a decoupled radiation model, in which no assumption of radiosity uniformity is required for the microscopic radiative exchange between particles, and establish a mapping between microscopic radiative view factors and macroscopic continuum dynamics based on the continuum-medium framework.MethodsThe radiation transfer was governed by a radially decaying function in HTGR. The resulting local radiative flux was determined by summing over the contributions of all particles within the interaction range. Then a radiation continuum-dynamics model applicable to engineering-scale pebble beds was derived to accurately capture the complex radiative interactions in the core, resolving the cross-scale theoretical gap between discrete particle systems and continuum representations. Finally, this model was applied to a 10 MW High Temperature Gas-cooled Test Reactor (HTR-10) for evaluation.ResultsResults show that for blackbody pebbles, the predicted radiative exchange factor is approximately 1.03, consistent with empirical models; for gray pebbles, the commonly used uniform effective radiation assumption fails to capture emissivity effects and leads to significant deviations from experimental observations. The model further reveals that radiative exchange in pebble beds is mainly confined within roughly 2.5 particle diameters.ConclusionsComparison with large-scale pebble-bed experiments demonstrates that the proposed model can reliably predict temperature distributions and thus offers strong engineering applicability, providing a new theoretical tool for understanding radiative heat-transfer mechanisms in HTGR cores and for supporting thermal-hydraulic design and safety analysis.  
    关键词：High-temperature gas-cooled reactor;Pebble bed;Thermal radiation;Heat transfer;Continuum dynamics model   
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    GUO Kailun, SUN Qishi, TANG Songsheng, ZHANG Jiarui, ZHANG Zhipeng, ZHANG Zeqin, HEI Zihao, TIAN Zhixing, WANG Chenglong, TIAN Wenxi

    DOI：10.3724/j.0253-3219.2026.hjs.49.260064
    摘要：High-temperature heat pipes, as highly efficient and passive phase-change heat transfer devices, play an irreplaceable role in nuclear reactor core cooling, spacecraft thermal management, and advanced energy systems. One of the key factors limiting their heat transfer performance lies in the capillary driving force and liquid-phase transport capability of the wick structure. Conventional wick designs suffer from an inherent trade-off between capillary pressure and permeability, which constrains the performance of high-temperature heat pipes under extreme heat fluxes and complex operating conditions. In recent years, nanostructure modification technologies have provided new pathways to overcome this bottleneck. This review systematically summarizes the research progress on high-temperature heat pipes with nanostructured wicks, covering the full research chain from microstructural fabrication and characterization, evaporation heat transfer mechanisms of alkali metals, macroscopic heat transfer performance experiments, to multiscale numerical simulations. Studies indicate that nanoscale structures constructed on wick surfaces via methods such as oxidation-reduction and sol-gel processing can simultaneously and significantly enhance capillary pressure and permeability, effectively reducing the thermal resistance of the evaporating meniscus. As a result, the startup speed, isothermal performance, and heat transfer limit of heat pipes can be improved by approximately 10%~40%. Molecular dynamics and lattice Boltzmann simulations reveal the critical influence of surface wettability on liquid sodium evaporation dynamics and flow spreading behavior, and experimentally correlated relationships for the contact angle as functions of temperature and pressure have been obtained. Moreover, multiscale numerical models based on computational fluid dynamics have been developed to predict the transient response and limiting behavior of heat pipes, further validating the heat transfer enhancement mechanisms induced by nanostructures. Finally, experimental studies on the adaptability of nanostructured-wick high-temperature heat pipes under complex operating conditions such as bending, motion, and thermal mismatch, are summarized, and future research challenges and development trends are discussed, including liquid metal flow and heat transfer mechanisms, the effects of non-condensable gases, strong transient and impact responses, high-fidelity code development, and data-driven predictive methodologies. This review aims to provide systematic theoretical insights and technical guidance for the design and application of next-generation high-performance high-temperature heat pipes.  
    关键词：High-temperature heat pipe;Nanostructured wick;Alkali-metal evaporation;Heat-transfer limit;Numerical simulation   
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    XING Mengjun, LI Jian, XIE Heng, SHI Lei

    DOI：10.3724/j.0253-3219.2026.hjs.49.250464
    摘要：BackgroundHigh-flux reactors, due to their extremely high neutron flux and diverse experimental functions, have more stringent requirements for design, construction, and operation than conventional research reactors. However, the current regulatory standards have limitations in terms of systematicity and applicability, making it difficult to effectively guide the safety regulation of such facilities.PurposeThis study aims to systematically identify the shortcomings of existing regulatory frameworks in their application to high-flux reactors and to propose a scientific and systematic regulatory framework so as to provide a reference for the development or revision of relevant technical standards, thereby enhancing regulatory effectiveness and ensuring the safe and sustainable development of high-flux reactors.MethodsFirstly, literature analysis was applied to a comparative study of domestic and international regulations. Then, case study analysis for comprehensively review of the existing regulatory frameworks was conducted and assessed its applicability to high-flux reactors. Finally, the gaps in the applicability of current regulations to high-flux reactors were identified.ResultsBased on these findings of literature analysis, case study and gaps identification, a hierarchical and well-structured regulatory framework is proposed to cover the entire lifecycle of high-flux reactors and emphasizes key aspects such as high-power-density core safety management, highly reliable radionuclide containment, and safety review of multifunctional irradiation experiments.ConclusionsThe proposed framework can effectively address the limitations of existing standards, offering solid regulatory support for the safe operation of high-flux reactors and the advancement of nuclear technology innovation.  
    关键词：High-flux reactors;Regulatory framework;Multi-tiered and coordinated framework;Graded and classified regulation   
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    DENG Yufeng, ZHANG Huang, LIU Ruiyang, LYU Meng, YIN Huaqiang, LI Jian, XIE Heng, SHI Lei

    DOI：10.3724/j.0253-3219.2026.hjs.49.250468
    摘要：BackgroundHigh-flux research reactors, operating as non-power reactors with neutron fluxes not less than 1×1014 cm-2∙s-1, play a vital role in scientific research, material property testing, and the production of radionuclides for medical and industrial applications. High-flux reactors predominantly employ plate-type fuel assemblies, featuring high core power density and more complex coolant flow conditions. Since traditional prediction methods exhibit significant errors in handling these complex geometries and non-uniform thermal loads, accurate critical heat flux (CHF) prediction remains a crucial requirement for core safety design and operation.PurposeThis study aims to enhance the prediction accuracy of CHF in narrow rectangular channels of plate-type fuel elements.MethodsFirstly, the CHF look-up table (LUT) database of the narrow rectangular channels of plate-type fuel elements was taken as the foundational dataset. An Extended Kalman Filter (EKF) was applied to dynamically correct and fuse the raw CHF-LUT data across various thermal-hydraulic conditions. Then, a Back Propagation (BP) neural network was constructed and trained using the EKF-processed dataset to capture the complex nonlinear relationships between operational parameters and CHF values. Finally, validation experiments were performed under specified operating conditions, and the prediction performance of the proposed EKF-ML model was systematically compared against both the direct CHF-LUT outputs and the traditional Sudo correlation.ResultsComparison results show that the EKF-ML model demonstrates a significant enhancement in prediction accuracy compared to both the direct CHF-LUT and the Sudo correlation. Specifically, the mean relative error of the predictions reaches 0.78%, and the relative root mean square error (rRMSE) decreases to 12.48% under the specified operating conditions.ConclusionsThis data-driven fusion EKF-ML approach proposed in this study provides a reliable and precise methodology for thermal-hydraulic analysis, offering new insights and methodologies for predicting CHF in narrow flow channels.  
    关键词：Narrow rectangular channels;Critical heat flux (CHF);Machine learning;Extended Kalman filter;CHF look-up table   
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