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• Formation and growth of fe-cr spinel layer follow a diffusion-controlled process. • Spallation and dissolution significantly degrade the fe-cr spinel layer over time. • Complex interplay between direct dissolution and spallation of oxide layer observed. • Microstructural evolution includes localized formation of Fe 3 O 4 and role of grain structure. • The dissolution rates of steel in LBE include contributions from direct dissolution and oxide scale loss. The application of Liquid Lead-Bismuth Eutectic (LBE) as a coolant in Lead-cooled Fast Reactors (LFRs) presents significant challenges due to its corrosive nature, especially at elevated temperatures. This study investigates the corrosion kinetics and mechanisms of 15–15Ti stainless steel in flowing LBE at 500 °C with oxygen concentrations ranging from 1 to 3 × 10−6 wt% and a flow rate of 1 m s-1. The research highlights the formation and growth of the Fe-Cr spinel oxide layer, which follows a parabolic rate law indicative of a diffusion-controlled process, crucial for long-term material stability predictions. Despite the initial effectiveness of the Fe-Cr spinel layer in mitigating corrosion, its integrity is compromised over time due to spallation and dissolution, allowing penetration of LBE elements and selective dissolution of Fe, Ni, and Cr. The study reveals a complex interplay between direct dissolution of steel components and spallation of the oxide layer, providing critical insights into material loss mechanisms and the degradation of structural materials in LBE-cooled reactors. [Display omitted] [ABSTRACT FROM AUTHOR]

This editorial discusses the technological advancements in Gen4 nuclear energy systems and small reactors. These advanced systems, such as sodium-cooled fast reactors, lead-cooled fast reactors, and gas-cooled fast reactors, offer superior sustainability, safety, reliability, and economics compared to current-generation systems. The article highlights specific research on the safety analysis of a lead-based reactor, the operational characteristics of a micro gas-cooled reactor, the flow stability of supercritical carbon dioxide in a Brayton cycle, and the fault diagnosis of rotating machinery using deep learning models. The authors hope that these articles will serve as a valuable reference for researchers in the field of Gen4 nuclear energy systems and small reactors. [Extracted from the article]

The energy conversion and utilization of liquid metals is becoming one of the effective ways to solve energy problems. The conversion and transfer of thermal energy from liquid metals to water are significant in advanced nuclear energy and metallurgy. It has been an urgent concern, especially in Generation IV of advanced nuclear energy systems‑lead-cooled fast reactors and the ultimate energy source for humanity-fusion engineering. In this paper, a large-scale liquid metal and water interaction test platform was developed to investigate the lead‑bismuth liquid metal and water interaction and the cover gas pressurization characteristics. Firstly, the evolution of phase behavior and water/vapor migration paths were inferred based on the transient temperature law. Secondly, the cover gas pressurization patterns above the molten pool were analyzed, and the test data showed three pressurization patterns, including two types of local vapor explosions. Additionally, this paper predicted the existence of another dangerous pressurization mode, i.e., overall vapor explosion. Finally, the cover gas pressurization rate model was established, and there is an appropriate matching between the model and test data with an average relative error of 12.6%. This paper provides an essential reference for profoundly understanding the energy conversion and thermal interactions between liquid metals and water. • A large-scale liquid metal and water interaction test platform was developed to investigate energy conversion and interaction. • Based on the transient temperature law, we discovered the gas-phase evolution characteristics during lead-water interaction. • Three different types of pressurization patterns of cover gas were identified. • A model of cover gas pressurization was developed to predict the pressurization rate. [ABSTRACT FROM AUTHOR]

It is of great significance to study the thermal-hydraulic characteristics of Lead-based Fast Reactor. In these years, the computational fluid dynamics method has become an attractive way in thermal-hydraulic and safety simulations of liquid metal cooled reactors. In order to investigate thermal-hydraulic characteristics of single-phase natural circulation flow in liquid metal cooled reactors, a self-developed CFD code was developed in this paper. The new code was proposed based on the two-phase compressible model, including liquid and vapor governing equations and a series of auxiliary models. The commercial CFD software ANSYS FLUENT was used to verify and validate the new code by comparing their simulation results under a typical heat driven cavity flow case. The comparison showed that the results simulated by the new code had good agreement with the ones calculated by ANSYS FLUENT. Furthermore, by coupling the above CFD model with the fuel pin heat transfer model, the application was conducted based on a full-scale reactor steady-state simulation of a natural circulation driven LBE-cooled fast reactor. From the results, it can be concluded that the new code can simulate and evaluate thermal-hydraulic behaviors of the LBE-cooled reactor well. [ABSTRACT FROM AUTHOR]

Natural circulation and forced circulation are two types of normal operation conditions that usually appeared in nuclear power systems. However, it should be noted that the reactor safety and reliability can be jeopardized due to significant fluctuation of the mass flow rate through the lead-based reactor core during the conversion from forced to natural circulation. Therefore, a model of 10MW th lead-based reactor based on RELAP5 mod4.0 is developed to analyze the effects of the five factors on the transient characteristics, including the power control system, the initial steady-state power level, the human intervention, shutting down each main pump one by one and the bypass of the main pump separately. The results show that using power control system can obviously reduce the transition time and realize the rapid response of the reactor during the conversion. Moreover, a higher initial power level results in a larger power fluctuation, a larger maximum value of cladding peak temperature and a stronger natural circulation. As a result, the maximum initial power level can be obtained according to the cladding temperature limitation (823 K). Especially, the optimized control strategy taking into account the combined effects of three factors, namely human intervention, shutting down each main pump one by one as well as the bypass of the main pump, can increase the maximum initial power level from 45%FP to 75%FP. • A RELAP5 model for a 10MWth lead-based reactor (CLEAR-I) was built to study the transient characteristics from forced circulation to natural circulation. • The effects of the five factors on the transient characteristics were analyzed separately. • The optimized control strategy taking into account the combined effects of three factors can increase the maximum initial power level from 45%FP to 75%FP. [ABSTRACT FROM AUTHOR]