An Iterational Physical Decoupling Method for Assessing the Safety of Deformed Fuel Channels

Abstract Irradiation during reactor operation causes continuous deformation in the fuel channels, resulting in narrowing of the control rod’s channels, which directly affects the safe insertion of the control rods. Faced with a multi-physics coupling scenario where the control rod is affected by flow resistance and channel resistance at the same time. This paper proposes a calculation scheme based on physical field decoupling and continuous iteration to calculate the rod dropping process in the deformed channels. Specifically, firstly, based on the empirical formula of the flow resistance, substitute the initial solution to estimate the flow resistance, and apply it to the control rod in the finite element method. Secondly, the finite element method is used to estimate the interaction force between the control rod and the channels, and then combining the flow resistance to obtain the time-velocity relationship (new solution). Thirdly, determine whether the iteration is terminated or return to the first step. Our study provides a solution to evaluate the safety of rod’s dropping process.