This study investigated the compatibility of lead with distinct crystal planes of Fe with a body-centered cubic (bcc) crystal structure and Ni with a face-centered cubic (fcc) crystal structure using molecular dynamics (MD) simulation. It was found that corrosion anisotropy depends mainly on the role of different crystal planes in regulating the spatial distribution of liquid lead. The essence of this regulation can be attributed to the interaction between the crystal plane and the liquid lead atoms. In consequence of the periodic arrangement of the crystal planes, the close-packed plane exhibits the highest atomic density and the widest interplanar distance. This configuration minimizes the interaction of the liquid lead atoms with the other crystal planes, thereby maximizing the regulatory effect on the distribution of the liquid lead atoms. The regulatory effect results in the formation of a regular layer-like distribution of the lead atoms, with a spacing between layers that is analogous to the crystal planes. This distribution mechanism effectively prevents the dissolution of atoms on the crystal surface into the liquid lead side by separating the atoms of the solid–liquid system from each other. Accordingly, for pure metals with a bcc crystal structure, corrosion resistance anisotropy indicates that the (111) plane is the most susceptible to corrosion, followed by the (001) plane, and the close-packed plane of (110) exhibits the most corrosion-resistant properties. As for fcc crystals, the corrosion resistance of the distinct planes is ordered as follows: (111) > (001) > (110).

Radioactive spent sodium is the product of liquid metal coolant generated in the decommissioning of fast reactors, and its safe and effective disposal is crucial for the success of the decommissioning. This work adopts solid-phase oxidation to process the liquid metal coolant from fast reactors, and the glass formers react with spent sodium at high temperature, forming a solidification body. The solid-phase oxidation treatment of radioactive spent sodium was experimentally investigated by reacting it directly with glass formers under high-temperature conditions (900–1200 °C). The phase composition and surface morphology of the solidification body were characterized using X-ray Diffraction (XRD) and Scanning Electron Microscopy (SEM). Mechanical properties were assessed via hardness testing, and thermal stability was monitored by ThermoGravimetric analysis (TGA). Compared with alkaline solution treatment of spent sodium, the results demonstrated that the solid-phase oxidation process yields a homogeneous glass phase without observable elemental volatilization at high temperatures. Furthermore, the effects of key variables, including different glass compositions and dwell times, on the structure of the solidification body were systematically examined.

The Bi/Bi₂O₃-type oxygen sensor is extensively employed for oxygen monitoring in liquid lead-bismuth eutectic (LBE)-cooled reactors, yet its low-temperature measurement accuracy remains a critical bottleneck limiting engineering deployment. This study aims to extend the lower operating temperature limit of the sensor through synergistic optimization of the reference electrode and solid electrolyte. The effects of the Bi/Bi₂O₃ mass ratio, filling amount, and yttria-partially stabilized zirconia (YPSZ) electrolyte wall thickness on sensor performance were systematically investigated over 300–600 °C. Electrochemical impedance spectroscopy and finite element simulations (COMSOL Multiphysics^® 6.3, COMSOL Inc., Stockholm, Sweden) were used to elucidate the underlying mechanisms. The results show that the optimized sensor with a Bi/Bi₂O₃ mass ratio of 95:5, a filling amount of 10 g, and a YPSZ wall thickness of 1.5 mm extended the stable operating limit from 350 °C to 300 °C, achieving a relative electromotive force error of 3.13% at 300 °C and maintaining over 4000 h of drift-free service. The improved low-temperature accuracy is attributed to the reduced oxygen ion migration activation energy (0.48 eV) and lower bulk impedance of the thick-walled YPSZ after high-temperature activation. These findings provide a material optimization strategy and theoretical basis for wide-temperature-range, long-lifetime oxygen sensing in lead-based reactors.

Accurate measurement of dissolved oxygen concentration in leadbismuth eutectic (LBE) is crucial for corrosion control and suppression of oxide impurities in advanced nuclear reactor systems. This study addresses the limitation of conventional Bi/Bi ₂ O ₃ oxygen sensors, whose accuracy degrades below 350°C, by developing novel sensors with optimized reference electrode filler mass and Bi/Bi ₂ O ₃ ratios. Specifically, an optimized sensor (denoted OS-5Y-1) with a bismuth filler mass of 10 g and a Bi/Bi ₂ O ₃ mass ratio of 95:5 demonstrated exceptional accuracy and stability down to 300°C. Performance was evaluated in static oxygen-saturated LBE across 300∼600°C. Results demonstrate that the redesigned sensors achieve: (1) Near-Nernstian EMF-temperature dependence within 300∼600°C, (2) <5% relative error between measured and theoretical EMF values, (3) <15% deviation in derived oxygen concentrations, and (4) Exceptional stability with EMF drift <1 mV during 40 h tests. Crucially, sensor OS-5Y-1 maintained high accuracy at 300°C (absolute error: 2.79 mV, 3.13% relative error), representing a breakthrough for low-temperature operation. Stepped thermal cycling revealed competing mechanisms affecting accuracy: inherent error increase at higher temperatures versus enhanced ionic conductivity from YPSZ electrolyte activation. These sensors enable reliable long-term oxygen monitoring in LBE systems, significantly advancing corrosion management for next-generation reactors.

The metallic fuel rod is a key component of the Integrated Fast Reactor (IFR) nuclear fuel assembly. To reduce the defects in the liquid sodium within the metallic fuel rod, the wetting behavior of liquid sodium on the surface of Cr12MoV steel has been studied, and the metallic fuel rod has been simulated. The results show that the smoother the surface of the sample, the easier it is for liquid sodium to wet the sample surface. Temperature is the primary factor influencing the wetting of liquid sodium on the sample. The higher the temperature, the better the wetting effect. 300°C is the critical temperature for whether liquid sodium can wet the sample; when the temperature is not higher than 300°C, the oxide film significantly hinders liquid sodium from wetting the sample. Compared to the open environment, a higher temperature is required inside the cladding to allow liquid sodium to flow into the gap between the cladding and the tungsten-copper pin.