{"title":"Machine learning-based water-level forecasting for marine steam generators under rolling conditions","authors":"Chenyang Wang, Jiawei Zhou, Yifan Xu, Genglei Xia, Minjun Peng","doi":"10.1016/j.nucengdes.2025.114513","DOIUrl":"10.1016/j.nucengdes.2025.114513","url":null,"abstract":"<div><div>In marine nuclear power plants, steam generator (SG) water level control is crucial for reactor safety, but it is challenged by two key factors: the transient inverse water level response to inventory changes under low-power conditions, and the superimposed influence of wind/wave-induced rolling motions. These factors induce nonlinear free surface fluctuations, rendering real-time measurement signals unreliable. While computational fluid dynamics (CFD) provides high-fidelity predictions, its high computational cost precludes real-time application. Conversely, traditional PID controllers struggle to handle these time-varying dynamics. This study employs Long Short-Term Memory (LSTM) and Backpropagation (BP) neural networks trained on CFD-simulated data to predict SG water levels under rolling conditions. The models leverage machine learning to capture sequential dependencies, mitigate measurement noise, and enable efficient real-time predictions. Validation results show that prediction errors are controlled within ±1.5 %, and the coefficient of determination (R<sup>2</sup>) exceeds 0.95. This confirms the superiority of neural networks in predicting SG water levels in complex marine environments.</div></div>","PeriodicalId":19170,"journal":{"name":"Nuclear Engineering and Design","volume":"445 ","pages":"Article 114513"},"PeriodicalIF":2.1,"publicationDate":"2025-10-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145267569","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
A. Jenet , P. Souček , K.-F. Nilsson , A. Caverzan , E. Capelli , P. Paviet , M. Rose , D. Holcomb , A. Smith , J. Křepel , F. Taucer , O. Beneš
{"title":"Advancing molten salt reactor technologies: Prioritizing standardisation needs and bridging gaps","authors":"A. Jenet , P. Souček , K.-F. Nilsson , A. Caverzan , E. Capelli , P. Paviet , M. Rose , D. Holcomb , A. Smith , J. Křepel , F. Taucer , O. Beneš","doi":"10.1016/j.nucengdes.2025.114495","DOIUrl":"10.1016/j.nucengdes.2025.114495","url":null,"abstract":"<div><div>This article outlines key standardisation needs for specific topics related to molten salt reactors (MSR), namely measurements of thermo-physical properties, safety evaluation, qualification of fuels and fuel cycles, and codes & standards for materials and components. It also explores strategies for bridging gaps in international standardisation, harmonisation and collaboration, and raises the importance of building MSR prototypes and investing in testing facilities. This article is based on a survey and direct inputs from a Putting Science into Standards workshop held on 18 and 19 March 2024 and organised by the European Commissions’ Joint Research Centre (JRC) and European Committee for Standardization (CEN) and European Committee for Electrotechnical Standardization (CENELEC). The workshop gathered 100 experts from research, industry and policy making to discuss the development and standardisation of MSR technologies. By working together at European and international levels, standardisation will be a key instrument to enable the development and commercialisation of mature MSR technologies to support the European Union’s goal of achieving fully functioning small modular reactors by 2030.</div></div>","PeriodicalId":19170,"journal":{"name":"Nuclear Engineering and Design","volume":"445 ","pages":"Article 114495"},"PeriodicalIF":2.1,"publicationDate":"2025-10-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145267624","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"The actual constraints and consequences of the maneuvering operation of PWRs — An optimum seeking approach","authors":"Pal Szentannai , Tamás Fekete","doi":"10.1016/j.nucengdes.2025.114480","DOIUrl":"10.1016/j.nucengdes.2025.114480","url":null,"abstract":"<div><div>Apart from the increasing share of uncontrollable renewables in the energy mix, and aside from the successive stopping of traditional, fossil-fueled power plants, the consumption–production balance of the grid must be permanently assured. This necessitates the controllability also of many nuclear power plants. Traditional load control solutions focus only on the controlled variable; as an upgrade, a more comprehensive optimum seeking approach is proposed by the current study. If a nuclear power plant is in the maneuvering regime, the actual constraints and consequences of the nonstationary transitions have to be recognized, formulated, and considered. The external expectations are stated from the grid operator’s side – generally as time-dependent constraints on the electrical load output. The internal aspects are the versatile side-effects of the transients, mostly caused by thermal stresses. For finding the optimal balance between fast electrical load change and low damage on the reactor-side, a cost function is needed, which considers and weights the consequences, while adhering to the constraints. The resulting actuator trajectories indicate that a simple slowing down of the reactor’s load change is far from the optimal load-following strategy.</div></div>","PeriodicalId":19170,"journal":{"name":"Nuclear Engineering and Design","volume":"445 ","pages":"Article 114480"},"PeriodicalIF":2.1,"publicationDate":"2025-10-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145267626","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Influence of aging on the dynamic behavior of reinforced concrete shear wall structures","authors":"Takaki Tojo , Yuki Idosako , Kazumasa Inoue , Takenori Hida","doi":"10.1016/j.nucengdes.2025.114488","DOIUrl":"10.1016/j.nucengdes.2025.114488","url":null,"abstract":"<div><div>The natural frequency of reinforced concrete buildings for nuclear power plants gradually decreases over time after their completion, mainly because of the shrinkage of the concrete during drying and minor damage caused by seismic forces. In this study, a numerical analysis method that comprehensively considers both drying shrinkage and seismic forces and investigates their effects is proposed. The results of finite element (FE) simulations performed with the proposed method show that when only the drying shrinkage of concrete is considered, the natural frequency decreases by 30 % and the damping constant increases by 300 % when the final shrinkage strain rate reaches 95 %. Furthermore, the natural frequency decreases by 50 % and the damping constant increases by 600 % when short-term seismic forces are applied, causing story drift angles of approximately 2 × 10<sup>–3</sup>. It was confirmed that these changes accelerate with repeated application of drying shrinkage and seismic forces. By comparing simplified simulations that consider the aging of stiffness and damping due to cumulative drying periods with FE simulations, seismic responses can be equivalently evaluated up to story drift angles of approximately 2 × 10<sup>–3</sup>, while responses beyond this are overestimated compared to FE simulation, allowing for conservative evaluations. This work has practical usefulness in that it enables bridging between complex modeling and simplified methods based on current design codes. The findings contribute to the establishment of seismic safety evaluation methods that adequately account for the effects of aging on reinforced concrete structures used over long periods of time.</div></div>","PeriodicalId":19170,"journal":{"name":"Nuclear Engineering and Design","volume":"445 ","pages":"Article 114488"},"PeriodicalIF":2.1,"publicationDate":"2025-10-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145221203","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Dynamic modeling and earthquake response of a novel tuned lever negative stiffness damper for vibration control in NPPs","authors":"Yang Liu, Hao Xu, Qiang Zhang, Wenguang Liu","doi":"10.1016/j.nucengdes.2025.114506","DOIUrl":"10.1016/j.nucengdes.2025.114506","url":null,"abstract":"<div><div>This study proposes a novel tuned lever–magnetically negative stiffness damper (TLNSD) for improving the seismic performance of structures, including both conventional buildings and nuclear power plant structures (NPPs). The TLNSD integrates a lever amplification device with a magnetically negative stiffness element to enhance the energy dissipation capacity of the system. The dynamic model of a single-degree-of-freedom (SDOF) structure with TLNSD is developed. Based on fixed-point theory and the H<sub>∞</sub> optimization criterion, analytical expressions for optimal damping and negative stiffness parameters are derived. Comparative analysis with the negative stiffness damper (NSD) and tuned inerter NSD (TINSD) shows that the TLNSD achieves superior vibration mitigation with lower damping and negative stiffness requirements. Additionally, it broadens the control frequency bandwidth and improves energy dissipation efficiency. Under both far-field and near-field pulse-like earthquakes, the TLNSD effectively reduces structural acceleration and displacement, with maximum reductions exceeding 60% in long-period conventional buildings. For multi-degree-of-freedom base-isolated NPPs, the TLNSD achieves up to 27% displacement reduction compared with the NSD. Lever amplification mechanisms and negative stiffness elements allow the TLNSD to significantly improve the energy dissipation capacity of its dampers. Although this study focuses on linear models, the TLNSD demonstrates strong potential as a compact, efficient, and cost-effective solution that enhances seismic protection across critical infrastructure.</div></div>","PeriodicalId":19170,"journal":{"name":"Nuclear Engineering and Design","volume":"445 ","pages":"Article 114506"},"PeriodicalIF":2.1,"publicationDate":"2025-10-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145221200","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Lian Chen , Zongyang Li , Kun Han , Chengcheng Deng , Xicheng Wang
{"title":"Numerical simulation for the thermal behavior of three-layer molten pool based on TROSE experiment","authors":"Lian Chen , Zongyang Li , Kun Han , Chengcheng Deng , Xicheng Wang","doi":"10.1016/j.nucengdes.2025.114508","DOIUrl":"10.1016/j.nucengdes.2025.114508","url":null,"abstract":"<div><div>In advancing the study of the In-Vessel Retention (IVR) strategy, a three-layer corium pool configuration has been proposed. Owing to density inversion and the thinning of the top metallic layer, the thermal focusing effect on the vessel sidewall becomes more pronounced, posing a higher risk to Reactor Pressure Vessel (RPV) integrity. To investigate the thermal behavior of this configuration, Computational Fluid Dynamics (CFD) simulations were conducted based on the TROSE experiment, which features a three-dimensional hemispherical vessel (diameter = 2.4 m) and employs mineral oil, water, and Cerrobend alloy as simulants. The results demonstrate that the Wall-Modeled Large Eddy Simulation (WMLES) turbulence model effectively captures the corium pool behavior under a Rayleigh number of 10<sup>15</sup>. Additionally, assuming only energy exchange (without mass transfer) across the interfacial boundaries is shown to be a reasonable simplification that improves computational efficiency. In Test-T3 of the TROSE experiment, strong natural convection in the light metallic layer produces a nearly uniform temperature field, whereas limited convection in the oxidic layer leads to significant thermal stratification. In the heavy metallic layer, heat transfer is dominated by conduction, accompanied by crust formation at the boundaries. These findings confirm the applicability of the CFD method for simulating three-layer molten pools and highlight its potential for future safety analyses in large-scale passive nuclear power plants.</div></div>","PeriodicalId":19170,"journal":{"name":"Nuclear Engineering and Design","volume":"445 ","pages":"Article 114508"},"PeriodicalIF":2.1,"publicationDate":"2025-10-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145221201","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Linear stability analysis of a HALEU-Fueled space nuclear reactor considering fuel composition and Xenon reactivity feedback effects","authors":"A.H. Raouf, G.R. Ansarifar, M. Rafiei","doi":"10.1016/j.nucengdes.2025.114503","DOIUrl":"10.1016/j.nucengdes.2025.114503","url":null,"abstract":"<div><div>A space nuclear reactor is an attractive choice for space applications such as planetary settlements and space exploration. For safe and reliable operation, stability analysis is inevitable. This paper, for the first time, presents the stability analysis of a space nuclear reactor considering various fuel compositions and different stability methods. To this end, the dynamics of a space nuclear reactor core designed with High-Assay Low-Enriched Uranium (HALEU) fuel are modeled using neutronic and reactivity feedback models. The stability analysis is carried out using linear stability methods. This comprehensive analysis provides crucial insights for the design and operation of space nuclear reactors, enhancing their safety and reliability for future space missions.</div></div>","PeriodicalId":19170,"journal":{"name":"Nuclear Engineering and Design","volume":"445 ","pages":"Article 114503"},"PeriodicalIF":2.1,"publicationDate":"2025-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145221202","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Research on Variations of floor response spectra under long-term operation of nuclear power plants","authors":"Chunlin Hou , Zhijun Dai , Xiaojun Li","doi":"10.1016/j.nucengdes.2025.114490","DOIUrl":"10.1016/j.nucengdes.2025.114490","url":null,"abstract":"<div><div>In recent decades, it has been a common international practice to extend the service life of operating nuclear power plants. The aging management of nuclear power plants is one of the key arguments for the life extension of nuclear power plants, and the evaluation of structures and equipment that meet the requirements of “no change in structure and characteristics when performing predetermined functions” and “no replacement based on appraisal life and specified time” in the screening results of aging management objects is the key technology for the life extension operation of nuclear power plants. However, the existing research on the aging of nuclear island plants and equipment mostly focuses on the prediction model of the performance changes of the materials themselves, and there are few studies on whether the nuclear island plants and pressure vessels can meet the original seismic performance evaluation after the aging effect. Based on the typical nuclear island plant structure, we analyzed the response characteristics of the nuclear island plant structure under different material properties in this study. The analyzed results show that the aging of reinforced concrete materials change and broaden the response of the nuclear island structure floor, and exceedances over the original design’s ± 15 % floor response spectra (FRS) uncertainty are significant in <strong>X</strong> (up to 51 %), <strong>Y</strong> (up to 22 %), and <strong>Z</strong> (up to 29 %). The nuclear island structure floor is the seismic input for the seismic performance evaluation of the pressure vessel, but existing studies overly focus on material degradation<!--> <!-->itself<!--> <!-->while neglecting seismic safety reassessment of critical structures (nuclear island, RPV). The research is therefore helpful to establish an FRS-envelope methodology for global LTO programs, which provides a technical basis for the subsequent life extension evaluations of nuclear power plants.</div></div>","PeriodicalId":19170,"journal":{"name":"Nuclear Engineering and Design","volume":"445 ","pages":"Article 114490"},"PeriodicalIF":2.1,"publicationDate":"2025-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145221209","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Jihun Im , Jae Hyung Park , JinHo Song , Sung Joong Kim
{"title":"Thermal performance evaluation of passive safety systems adopting phase change material applicable for passive molten salt fast reactor","authors":"Jihun Im , Jae Hyung Park , JinHo Song , Sung Joong Kim","doi":"10.1016/j.nucengdes.2025.114497","DOIUrl":"10.1016/j.nucengdes.2025.114497","url":null,"abstract":"<div><div>Phase Change Materials (PCMs) have been widely applied across industries involving thermal energy management. In this study, we propose a decay heat removal system concept using PCMs. The thermal performance of the passive safety system (PSS) incorporating PCMs is evaluated for a target reactor. The reference design is the Passive Molten salt Fast Reactor (PMFR), a prolonged long-life core design that deliberately excludes online fuel purification systems. However, the accumulation of fission products in such systems introduces significant challenges for decay heat removal, which this work aims to address. The PCM-based PSS proposed in this paper is expected to resolve these challenges by providing both effective insulation during normal operation and effective decay heat removal during off-normal conditions. To investigate its feasibility, a lumped-parametric analysis is conducted to evaluate the thermal performance of the PCM-based PSS, focusing on heat loss reduction and residual heat removal capacity. The analysis results suggest that a significant reduction of heat loss from 0.42% to 0.114% of nominal power is achievable, while decay heat can be removed effectively during off-normal conditions. We perform parametric studies to assess the effect of PCM properties and system geometry on thermal performance, highlighting the significance of selecting appropriate PCM materials and its optimized geometrical design. The findings suggest that PCM-based PSS can enhance both safety and efficiency of PMFR.</div></div>","PeriodicalId":19170,"journal":{"name":"Nuclear Engineering and Design","volume":"445 ","pages":"Article 114497"},"PeriodicalIF":2.1,"publicationDate":"2025-09-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145221269","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Soon K. Lee , Yinbin Miao , Aaron J. Oaks , Shipeng Shu , Abdellatif M. Yacout , Jason Rizk , John Bolin , Christopher Ellis , Hangbok Choi
{"title":"Transient fuel performance analysis for the preliminary fuel concept of general atomics fast modular reactor","authors":"Soon K. Lee , Yinbin Miao , Aaron J. Oaks , Shipeng Shu , Abdellatif M. Yacout , Jason Rizk , John Bolin , Christopher Ellis , Hangbok Choi","doi":"10.1016/j.nucengdes.2025.114494","DOIUrl":"10.1016/j.nucengdes.2025.114494","url":null,"abstract":"<div><div>This study investigates the transient fuel performance of General Atomics Fast Modular Reactor (GA-FMR) during accident scenarios, focusing on the behavior of its innovative fuel system that combines high-assay low enriched uranium dioxide (HALEUO2) fuel with SiGA® ceramic matrix composite silicon carbide cladding. The preliminary fuel design’s response was analyzed during reactivity-initiated accidents (RIA) and loss of coolant accidents (LOCA) using BISON fuel performance analysis code, which included both the diffusion enhanced and BISON-FASTGRASS coupled UO<sub>2</sub> models. The RIA analysis demonstrated that effective reactivity control reduced fuel temperature, though with transient fission gas release resulting in additional tensile stress state on the cladding. LOCA simulations revealed differing predictions between the two models: the BISON UO<sub>2</sub> model showed more transient fission gas release but minimal pellet expansion, while the BISON-FASTGRASS UO<sub>2</sub> model predicted less pronounced fission gas release but more fuel swelling and thermal expansion, potentially leading to pellet-cladding mechanical interaction. These findings highlight critical areas for fuel design optimization and identify knowledge gaps requiring further experimental and computational investigation to advance GA-FMR fuel development.</div></div>","PeriodicalId":19170,"journal":{"name":"Nuclear Engineering and Design","volume":"445 ","pages":"Article 114494"},"PeriodicalIF":2.1,"publicationDate":"2025-09-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145221207","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}