Development and Validation of Thermal-Mechanical Creep Failure Module for Reactor Pressure Vessel Lower Head

Abstract

For severe accidents, in-vessel retention (IVR) is a very effective and crucial severe accident mitigation measure. The lower head of the reactor pressure vessel plays a vital role in the IVR strategy. The failure of the lower head may lead to the release of radioactive substances into the environment. During the implementation of IVR, the lower head is in a high-temperature environment, and its main failure form is creep failure. Therefore, to ensure the successful implementation of the IVR strategy and prevent radioactive material leakage, it is necessary to conduct an in-depth analysis of the lower head. In this paper, the lower head thermal-mechanical creep failure (LHTCF) module is developed based on the theory of plate and shell and Norton-type constructive creep laws. Through the mechanical analysis of the lower head, seven failure criteria are used to evaluate the integrity of the lower head. Finally, the LHTCF module is integrated into the integrated severe accident analysis (ISAA) program, and the accuracy of the module is validated by numerical calculation of the Organisation for Economic Co-operation and Development Lower Head Failure (OLHF) experiment. Through the comprehensive judgment of different failure criteria, the final simulation results are in good agreement with the experimental data. The results show that the wall thickness at the crack decreases sharply before failure due to the effect of creep, and the stress increases abruptly at the failure time. The LHTCF module developed in this paper can accurately predict the creep behavior of the lower head, and the calculated failure time, position, and thickness distribution agree well with the experimental results.

Keywords:

• Severe accident
• in-vessel retention
• lower head
• creep failure
• Organisation for Economic Co-operation and Development Lower Head Failure experiment

Acknowledgments

Author credit contribution statement: Hao Yang: investigation, methodology, organize data, prepare the first draft;. Bin Zhang: investigation, methodology, supervision; Pengcheng Gao: methodology, modify paper; Runze Zhai: modification of experimental numerical model; and Jianqiang Shan: supervision.

Disclosure Statement

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Additional information

Funding

This work was supported by the the National Key Research and Development Program of China (no. 2019YFE0191600).