Session: 07-13: SMR and Advanced Reactors - II

Paper Number: 136020

136020 - Study on the Oxidation/corrosion Behavior of Small Modular Lead-Bismuth-Cooled Fast Reactor Summer 

Abstract: 

The lead-cooled fast reactor (LFR), as one of the candidate reactor types for the fourth generation, possesses advantages such as favorable neutron economy, high passive safety, and a simple system structure. To meet the stable energy supply needs in remote or wilderness areas, the University of Science and Technology of China (USTC) and China Nuclear Power Technology Research Institute have developed a lead-bismuth-cooled, pool-type, small modular fast reactor named the Sustainable Modular Mobile Enhanced Reactor (SUMMER). It features a long operational lifespan (exceeding ten years), a compact core, modular design for scalable production, rapid installation, mobility, inherent safety, and cost-effectiveness. However, the lead-cooled fast reactor faces a significant challenge of oxidation/corrosion issues. The oxidative/corrosive behavior of liquid lead-bismuth towards materials leads to the degradation of structural material performance and a substantial reduction in the reactor's operational lifespan. Given SUMMER's extended design life, corrosion becomes particularly pronounced. To ensure the operational lifespan of SUMMER and mitigate the impact of oxidation/corrosion on structural materials, it is essential to simulate and analyze the mass transfer of oxidation/corrosion products and the corresponding oxidative/corrosive behavior in the reactor core. Addressing this challenge, the USTC has developed a novel oxygen transport-oxygen corrosion computational analysis program named KMC-SUBtra-MC. This program enables the study of the thermal characteristics, oxygen transport, and oxidation-corrosion evolution of the reactor core during long-term operation. To enhance the realism of mass transfer simulation within the LFR, a computational fluid dynamics (CFD) program, TrioCFD, has been coupled using the ICoCo interface. Utilizing this coupled system, an oxidation/corrosion analysis was performed on SUMMER, and the preliminary calculation of its oxygen concentration distribution was conducted. Parameters such as the oxide layer thickness, velocity, temperature, and oxygen concentration of the reactor core were obtained. The results indicate that during SUMMER operation, the oxidative/corrosive effects lead to the formation of a dual-phase oxide film, with the thickness distribution of the oxide film being similar to the power distribution. In the early stages of reactor operation, the oxidation of fuel cladding follows a parabolic law, resulting in a higher oxygen consumption rate. Dissolved oxygen in the coolant is nearly depleted, accelerating the corrosion of structural materials. The reactor core components experience an oxygen depletion period, the duration of which is correlated with the temperature of the core components. The oxygen concentration in the coolant leaving the reactor core differs significantly from that inside the reactor pool, leading to a stratification phenomenon between the heat exchanger and the pressure vessel. As time progresses, the slope of the parabola decreases, and the oxidation rate of the reactor core slows down. The oxygen concentration at the reactor core outlet gradually increases. To mitigate the corrosion caused by oxygen concentration depletion, a pre-oxygenation scheme for fuel before insertion has been proposed. Using the coupled system, the analysis of this scheme reveals a significant reduction in the initial oxygen consumption, preventing oxygen depletion. The oxygen concentration difference between the coolant leaving the reactor core and that inside the reactor pool diminishes, and the stratification phenomenon between the heat exchanger and the pressure vessel disappears. Pre-oxygenation proves beneficial in reducing the risk of steel corrosion due to oxygen deficiency.

Presenting Author: Kefan Zhang University of Science and Technology of China

Presenting Author Biography: Doctorial Student of University of Science and Technology of China

Authors:

Junjia Zhang University of Science and Technology of China
Kefan Zhang University of Science and Technology of China
Hongli Chen University of Science and Technology of China