Scientists Have Found Out Which Nuclear Reactor Heat Exchanger Defects Are Critical

10:34, May 8, 2024

The research was conducted by Russian and Chinese specialists

Scientists from UrFU and North China University of Water Resources and Electric Power (Zhengzhou) have found out which defects in the surface of a nuclear reactor heat exchanger are critical for liquid metal embrittlement. The researchers conducted computer modeling of the process of interaction of liquid metal coolant (Pb and Pb55Bi(e) melt) with a steel heat exchanger in the cooling device of a nuclear reactor. The results were presented at the conference "Surface Phenomena in Dispersed Systems" and in a scientific article in the Colloid Journal.

"The work was done in collaboration with Wang Veishu, a professor in the Department of Energy and Technical Thermophysics at the North China University of Water Resources and Electric Power. Previously, Wang Veishu's research group experimentally found that liquid metal (Pb55Bi) penetrated 316L steel at 823 Kelvin for 1000 hours to a depth of 94 μm. Since it is extremely difficult to conduct a full-scale experiment, we then evaluated the possibility of liquid metal heat exchanger failure theoretically using computer modeling. We found that a defect in the surface of the steel heat exchanger in the form of a 0.15 mm deep risk can be the cause of failure of nuclear reactor coolers due to the effect of liquid metal embrittlement. The data we obtained will be useful in designing cooling systems for nuclear reactors with liquid metal coolant", explains Olga Chikova, co-author of the study and professor at the UrFU Department of Physics.

Liquid metals are used as coolants in the nuclear power industry. However, they can interact with the heat exchanger material causing corrosion and liquid metal embrittlement. The mechanism of liquid metal embrittlement is based on a decrease in the bonding of solid atoms due to the adsorption of liquid metal on the crack surface (Rehbinder effect). The decrease in the surface energy of the solid-liquid interface caused by adsorption leads to a decrease in the critical stress required for crack propagation. The liquid metal penetrates the steel by capillary action. Typically, cracks nucleate at defects in the heat exchanger surface and propagate along grain boundaries due to their wetting by the liquid metal. It is important to determine which defect on the heat exchanger surface (e.g., a certain depth of risk) may be the cause of failure of nuclear reactor coolers due to liquid metal embrittlement.

Reference

At the meeting of the BRICS Network University in 2023, the Ural Institute educational project, implemented by the Ural Federal University and the North China University of Water Resources and Electric Power, was recognized as the best transnational educational project. The Ministry of Education of the People's Republic of China has set the task of developing the project into joint scientific research. In this regard, a scientific group was created to study the modeling of the interaction of liquid metals with reactor steel.

Alena Nevolina

The news article was translated by UrFU International Marketing Office.
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