Session: 04-06: SMRs, Advanced Reactors and Fusion

Paper Number: 132023

132023 - Performance Analysis and Optimization Scheme Evaluation of Control Rod Drop Collision in Gas-Cooled Microreactor 

Abstract: 

In the case of rod drop accident in high temperature gas-cooled reactor, the control rod is completely inserted into the core in a state of approximate free fall by its own gravity, thus realizing reactor shutdown. In this process, the control rod will generate great kinetic energy with the falling process, and it will impact with the lower reflector of the reactor, resulting in the destruction of graphite and control rod structure in the reflector, and it is impossible for graphite components to be repaired within the service life, and the control rod is not easy to be replaced, so it is urgent to study and optimize the collision between the lower end of the control rod and the graphite reflector in the rod falling accident.

At present, there are many kinds of cushioning devices in engineering to alleviate the impact. It is common to fill foam-like materials or honeycomb-like materials between the two interfaces where the impact occurs, so as to absorb the impact load and realize the protection of components.However, due to the particularity of high temperature and long life of nuclear reactors, the above-mentioned solution using filling materials cannot be adopted. In addition, there is a scheme of using crush elements. At present, some scholars have studied the theoretical model and numerical simulation of crush shell. In the field of reactors, the scheme of buffering together with fluid resistance in pressurized water reactors and arranging crush elements on the bottom reflection layer of the core in high temperature gas-cooled reactors is widely used. However, the two schemes are not suitable for the core design of high-temperature gas-cooled reactor with high temperature, and are not easy to take out and replace, so their adaptability is limited.

 In this paper, ANSYS/LS-DYNA finite element simulation program is used. Firstly, the optimization effects of the innovative spring-type and cylindrical thin-wall crushing buffer structures are compared, and then the influence of wall thickness on collision and thin-wall deformation is studied with emphasis on the scheme of cylindrical thin-wall crushing buffer mechanism. It is found that both the cylindrical thin-walled tube and the spring have obvious optimization effects on the collision, but the rebound of the cylindrical thin-walled tube scheme is smaller after the collision. The wall thickness of cylindrical thin-walled cylinder has a great influence on the maximum stress and graphite layer stress of the rod, but has a relatively small influence on the rebound of the rod, and there is an optimal optimization scheme.

Keywords: Control rod; Rod falling accident; Collision

Presenting Author: hao Dong CNPE

Presenting Author Biography: Engaged in nuclear reactor fuel assemblies and related components.

Authors:

hao Dong CNPE
Anzhou Qi CNPE
Xiaochuan Jiang CNPE