Nuclear Techniques ›› 2016, Vol. 39 ›› Issue (10): 100603-100603.

• NUCLEAR ENERGY SCIENCE AND ENGINEERING •

### Pressure vessel deformation under in-vessel retention condition

WEN Shuang, LI Tieping, LI Congxin, GAO Xinli

1. Nuclear and Radiation Safety Center, Ministry of Environmental Protection, Beijing 100082, China
• Received:2016-03-28 Revised:2016-06-16 Online:2016-10-10 Published:2016-10-13
• Supported by:

Support by National Science and Technology Major Project (No.2013ZX06002001-003)

Abstract:

Background: In-vessel retention (IVR) has become an important severe accident mitigation strategy for advanced light water reactor in recent years. The successful implementation of IVR depends on the external reactor vessel cooling (ERVC) technique. In case of core melt, the bottom head of reactor pressure vessel (RPV) becomes deformed due to the thermal impacts of high temperature, and causes the narrowing of external coolant channel which is the gap between pressure vessel outer wall and insulation layer. This phenomenon could lead to local heat transfer deterioration and then causes the failure of IVR. Purpose: The aim of this paper is to analyze the deformation of reactor pressure vessel under IVR condition. Methods: The thermal and mechanical calculations of reactor pressure vessel are performed by using the finite element methods. This work can be divided into two steps. The first step is the evaluation of the thermal field of RPV, and the second step is the calculation of stress and displacement of RPV based on its temperature fields. Results: The result shows that the maximum vertical deformation of RPV caused by the thermal dilatation is 13.11 mm, while the deformation caused by the other mechanical loads is only about 0.61 mm. After 100-h, the creep leads the vertical deformation increases to 13.85 mm from 13.72 mm. The size reduction of external coolant channel due to the reactor pressure vessel deformation is between 13.85 mm and 18.75 mm. Conclusion: With internal pressure of 1 MPa, the deformation of reactor pressure vessel produced by high temperature creep increases as time increases, but the value remains small. The thermal dilatation is the most important factor of the reactor pressure vessel deformation under IVR condition.

CLC Number:

• TL351+.6