Status and Perspective of China’s Nuclear Safety Philosophy and Requirements in the Post-Fukushima Era

The significant impact brought by a severe nuclear accident at the Fukushima Daiichi Nuclear Power Plant (NPP) in Japan in March 2011 has made global regulators to review the requirements against severe accidents. In China, comprehensive safety inspection and external hazard safety margin assessment on NPPs were carried out, regulatory requirements on improvement measures for NPPs based on the inspection were given, the nuclear safety 5-year plan was made and executed, and the safety requirements on the new NPP design were drafted. The Nuclear Safety Law came into effect in 2018. The “Code on the Safety of Nuclear Power Plant Design” (HAF102) was revised in 2016, and relevant safety guides were developed. In this article, improvement actions and requirements about NPP safety in China over the past 10 years were reviewed, and the nuclear safety philosophy and requirements including practical elimination, classification of accident conditions, and defense in depth portable equipment were elaborated. In summary, some suggestions of NPP safety in China in the future were provided.

Pressure Tuned Structural, Electronic and Elastic Properties of U3Si2C2: A First Principles Study

U3Si2C2 is expected to be a new nuclear fuel as a ternary compound of uranium, silicon and carbon. However, the relevant research on U3Si2C2 under accident conditions is rarely reported. Hence it is necessary to explore the service behavior of the potential U-Si-C ternary nuclear fuel in extreme environments. In this work, the structural characteristics, electronic behaviors and mechanical properties of U3Si2C2, such as stable crystalline structures, density of states, charge distributions, electron localization function, electronic thermal conductivity and elastic modulus under extreme high pressure are calculated by density functional theory. The calculation results show that the lattice volume sharply increases when the external stress reached 9.8 GPa. Ionic and metallic nature coexist as to the bonding characteristics of U3Si2C2, and the ionic takes the dominant position in bonding. The toughness of U3Si2C2 is predicted to be better compared to U3Si2. Our theoretical investigation may help with the application of U3Si2C2-based fuel and the design of ternary uranium fuels.

The H2020 McSAFER Project: Main Goals, Technical Work Program, and Status

This paper describes the main objectives, technical content, and status of the H2020 project entitled “High-performance advanced methods and experimental investigations for the safety evaluation of generic Small Modular Reactors (McSAFER)”. The main pillars of this project are the combination of safety-relevant thermal hydraulic experiments and numerical simulations of different approaches for safety evaluations of light water-cooled Small Modular Reactors (SMR). It describes the goals, the consortium, and the involved thermal hydraulic test facilities, e.g., the COSMOS-H (KIT), HWAT (KTH), and MOTEL (LUT), including the experimental programs. It also outlines the different safety assessment methodologies applied to four different SMR-designs, namely the CAREM (CNEA), SMART (KAERI), F-SMR (CEA), and NuScale. These methodologies are multiscale thermal hydraulics, conventional, low order, and high fidelity neutron physical methods used to demonstrate the inherent safety features of SMR-core designs under postulated design-basis-accident conditions. Finally, the status of the investigations is shortly discussed followed by the dissemination activities and an outlook.