The Coupling State Equations and the Symplectic Algorithm for Control Rod Drop and Fluid Flow

Abstract

In this paper, a nonlinear state equation describing the coupling between control rod drop and fluid flow was proposed to solve the problem of control rod drop in nuclear reactor. The state equation has a uniform format for different fluid states in the process of control rod drop, which can conveniently deals with the problem for different working conditions. In order to efficiently analyze the falling process, accurately capture the sudden change of flow state and ensure the numerical stability of time integral, an adaptive time step preserving algorithm is proposed in this paper. Numerical examples show that the numerical model proposed in this paper can accurately calculate the key data such as displacement, velocity, acceleration and falling time of the control rod in the falling process with a large time step, and the calculated results are in good agreement with those obtained by commercial software.