Session: 01-04: Nuclear Plant Operation, Modification, Life Extension, Maintenance and Life Cycle - IV

Paper Number: 134800

134800 - Research on Sealing Performance and Electrical Performance of Low Voltage Electrical Penetrations Assembly in Containment After Severe Accidents 

Abstract: 

The containment of a nuclear reactor is the third safety barrier to prevent the leakage of radioactive materials into the environment. Under severe accident conditions, the containment of a nuclear reactor is subjected to high-energy loading conditions of high temperature, high pressure, high humidity, and high dose rate irradiation, posing a great threat to the integrity of the containment. The Electrical Penetration Assembly (EPA) is a part of the containment vessel that provides an electrical path for conductors to pass through the containment vessel. There are mainly two types of EPA: medium-voltage EPA and low-voltage EPA. Medium-voltage EPA provides three-phase power to the reactor coolant pump motor, with a rated transmission voltage of 6600V. Low-voltage EPA is mainly used for connecting low-voltage power circuits, control and instrument circuits, and coaxial and tri-coaxial cable circuits, with a rated transmission voltage of 380V. Low-voltage EPA is composed of stainless steel cylinders, conductor components, etc. Among them, the polyether ether ketone (PEEK) special engineering plastic filled inside the conductor components carries out the sealing function. According to GB13538, the EPA must ensure reliable sealing under various accident conditions while meeting relevant electrical performance requirements. Therefore, it is necessary to research low-voltage EPA's internal sealing material performance. By investigating the development history of sealing materials filled in containment EPA at home and abroad, experimental research on the comprehensive sealing performance of low-voltage EPA after serious accidents was conducted using ultra-high temperature and high-pressure accident simulation circuits. Insulation resistance testers were used to detect the electrical signals between the penetrating conductor and the stainless steel cylinder and between the penetrating conductor and the ground. The research results indicate that with the development of materials science, there have been significant changes in the sealing materials used for low-pressure EPA filling. The sealing materials used for low-pressure EPA include ethylene propylene rubber, cross-linked polyolefin, polysulfone, and the widely used PEEK material; Based on the double-layer design of the containment, the low-pressure EPA have a similar shape and structure, both of which are cylindrical stainless steel containers that bear pressure internally; After low-pressure EPA is maintained for 72 hours at a temperature of 200 ℃, a pressure of 0.6Mpa, and a water vapor to air ratio of 0.8:0.2, the leakage rate is 2.75 × 10^-6Pa · m ³/ S; The insulation resistance value between the penetrating conductor and the stainless steel cylinder is greater than 2 × 10⁹ Ω, the insulation resistance value between the conductor and the ground is greater than 2 × 10⁹ Ω, the tested EPA has excellent sealing and electrical performance, still meeting the requirements of engineering applications.

Presenting Author: Yanlu Wang Harbin Engineering University

Presenting Author Biography: Name: Wang Yanlu
Age: 25 years old
Institution: School of Nuclear Science and Technology, Harbin Engineering University
Grassroots organization: Nuclear Power Plant Research Institute
Education: PhD in progress
Research direction: Severe accident mitigation technology

Authors:

Yanlu Wang Harbin Engineering University
Xinli Yu China Nuclear Power Engineering Co.,Ltd.
Xiaxin* Cao Harbin Engineering University
Yu Liu China Nuclear Power Engineering Co.,Ltd.