비안전 전력계통 4.16kV 모선 저전압 발생에 따른 원자력발전소 영향 평가에 관한 연구

Abstract

ABSTRACT

A Study Regarding Evaluation of Impact on Nuclear Power Plants According to Occurrence of Low Voltage in 4.16 kV Bus of Non-Class 1E Electric Power Supply System

By Jung, Hyoung Duk Adviser : Prof. Song, Jong Soon, Ph. D. Department of Nuclear Engineering, Graduate School of Chosun University

Beginning with the commercial operation of KORI # 1 nuclear power plant, the first nuclear power plant in Korea, on April 1978, total 21 nuclear power plants including SHIN-KORI #1 are currently being operated for commercial purpose. During the period of 33 years, there have been a number of abnormal occurrences and failures, and based on such trials and errors, the procedures for abnormal occurrence have been prepared for each nuclear power plant. Despite of know-how for 33 years, however, accidents beyond the range of the procedures for abnormal occurrence occasionally occur. Recently, during the power set-back to perform the 12th preventive maintenance in Yeonggwang #3, there was an abnormal occurrence in its electric power supply system. While performing non-essential power transfer to the start-up transformer from the auxiliary transformer at 32% output, non-class 1E class 13.8 kV non-essential power was lost due to a failure in the interlock logic system card. Low voltage in the bus caused the shut down of the reactor coolant pump, and the reactor could be maintained in a safe manner according to the related emergency procedure. However, as non-class 1E 4.16 kV power failed to fast transfer to the start-up transformer from the auxiliary transformer and the resulted low voltage brought about difficulty to recover the secondary system of the nuclear power plant. For this reason, to search similar abnormal cases were tried in other local or foreign nuclear power plants, data regarding abnormal occurrence in the electric power supply system have been limited to class 1E power loss and there was no nuclear power plant which operates the procedures for abnormal occurrence for non-class 1E power loss. If such an abnormal accident occurs in the non-class 1E power supply facility during normal operation, it is judged to have a difficulty in finding actual status of the plant. The need for preparing the applicable procedure for abnormal occurrences has been raised in order to systematically analyze the inoperability condition of non-class 1E loads and to provide for abnormal occurrences in the electric power supply system. Actual power loss simulation was carried out using a simulator, and based on this result, the procedure for abnormal occurrence(N-1E 4.16 kV bus low voltage) was developed. It is expected to spread this procedure to other nuclear power plants in future, and to contribute to their safe operation and utilization for education data including image training for operators.