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The development of advanced nuclear energy systems imposes stringent requirements on the service stability of nuclear materials under extreme environments characterized by multiple stressors. Continuous silicon-carbide-fiber-reinforced silicon carbide (SiCf/SiC) ceramic matrix composites possess advantages such as low density, excellent high-temperature mechanical properties,corrosion resistance, and irradiation tolerance. Furthermore, SiCf/SiC composites demonstrate a pseudo-ductile fracture behavior under external forces, positioning them as highly promising structural materials for advanced nuclear energy systems. This study systematically summarizes the fundamental research framework on nuclear-grade SiCf/SiC composites at the material, component,and service performance levels. It also analyzes the developmental trends in this field among traditional nuclear powerhouses such as the United States, France, and Japan, as well as in other emerging nuclear energy countries and China. Furthermore, the study identifies existing issues and challenges faced by China’s nuclear-grade SiCf/SiC sector in terms of raw materials, data accumulation,and patent standards, and proposes targeted measures and suggestions: (1) strengthening the research and development of material preparation technologies, (2) developing a new paradigm of research and development, (3) reinforcing the industry-universityresearch-application cooperation, and (4) enhancing international exchanges on the basis of maintaining independence. The aim of the study is to provide guidance and reference for the research directions and policy-making in China’s nuclear-grade SiCf/SiC sector.

.A lead-based reactor with employing heat pipes as passive residual heat removal system (PRHRS) for longterm decay heat removal was designed. Three-dimensional computational fluid dynamics (CFD) software FLUENT was adopted to simulate the thermal-hydraulic characteristics of the PRHRS under Station-Black-Out (SBO) accident condition. The results showed that heat in the core could be removed smoothly by the PRHRS, and the core temperature difference is less than 20 K.

Considering that many parameters with mutual influence which were difficult to be considered comprehensively were involved in the optimization design of thermoelectric power generation system, a method that can calculate the optimal design scheme quantitatively according to the heat source characteristic was proposed in this work. The optimum working temperature of the thermoelectric module was determined by coupling the measured thermoelectric module performance curve with the temperature relationship of the cold and hot ends under the design condition. Then, based on the iterative method, the influence of various fin radiator structural parameters on heat dissipation performance was quantitatively analyzed by FLUENT software, so as to deliver the best combination of radiator parameters. The results showed that under the condition of constant heat flux density of 36 kw/m2, in order to obtain the best system efficiency, the cold end temperature should be controlled as 50 oC, and the fin radiator base thickness, fin spacing and fin height of the matched radiator should be 8 mm, 3 mm and 90 mm respectively.

The effects of pre‐exposure and surface notch on the tensile properties of T91 steel in oxygen saturation lead–bismuth eutectic (LBE) have been investigated by slow strain rate tensile tests at 350°C with a strain rate of 1 × 10−5 s−1, and the reference tests were performed in Ar gas. The pre‐exposure was conducted in liquid LBE at 500°C with an oxygen concentration of 10−8 wt% for 500 h. It is shown that the tensile properties of the nonpre‐exposed specimens whether with or without a notch were not affected by LBE, but obvious liquid metal embrittlement (LME) was observed on the pre‐exposure specimens. After being pre‐exposed, the notched one was more prone to liquid LBE embrittlement compared to the unnotched specimen. Morphology similar to fatigue striations was observed on the fracture surface of the notched specimen with pre‐exposure, which was probably attributed to the rapid growth of the crack. The results revealed that pre‐exposure had a critical effect on LME, and surface notch intensified this phenomenon when pre‐exposure was present. [ABSTRACT FROM AUTHOR]

Corrosion tests of T91 were carried out in the stagnant lead–bismuth eutectic (LBE) containing 10−6, 10−7, and 10−8 wt% oxygen at 500°C for up to 2000 h, respectively. The dependence of corrosion characteristics on oxygen concentrations in LBE was obtained. The results show that the oxide‐scale structure changes from a three‐layer magnetite/spinel/internal oxidation zone (IOZ) scale under the oxygen concentration of 10−6 wt%, to the formation of a two‐layer spinel/IOZ scale under the oxygen concentrations of 10−7 and 10−8 wt%. In addition, with the decrease of the oxygen concentration, the Cr/Fe ratio in the Fe–Cr spinel slightly increases in a linear rule while the thicknesses of the oxide layers gradually decrease. [ABSTRACT FROM AUTHOR]