원자력발전소용 안전등급 케이블의 경년열화에 따른 연소 및 연기특성 분석

Analysis of Combustion and Smoke Characteristics According to the Aging of Class 1E Cables in Nuclear Power Plants

본 연구에서는 원자력 발전소에서 사용되는 안전등급 케이블을 대상으로 경년열화에 따른 연소 및 연기특성을콘 칼로리미터 시험을 통해 분석하였다. 열발생률의 1st peak 구간인 초기 특성의 경우, 비열화 케이블이 열화 케이블에 비해 20-50 kW/㎡ 높게 측정되었으나, 2nd peak인 중/후기에는 열화에 따른 난연성능의 저하에 기인하여 비열화케이블에 비해 열화 케이블들이 높게 측정되었다. 또한, Char 층이 불안정하게 형성됨에 따라 char 층의 유지시간이비열화 케이블에 비해 열화 케이블들이 약 200 s 단축됨을 확인하였다. 총발열량은 열화 케이블이 비열화 케이블에비해 약 1.4배 높게 측정되었다. 연기특성의 경우, 연기발생률은 열발생률과, 총 연기발생량은 총발열량과 비슷한 양상을 띄며, 총 연기발생량은 열화 케이블이 비열화 케이블보다 높게 측정되었다. 연기인자는 열화 기간이 증가함에따라 증가하는 경향성을 보였으며, 4년 이상 열화된 케이블들은 비열화 케이블에 비해 약 1.76-2.0배 정도 차이가 났다. 따라서 경년열화가 진행된 케이블일수록 열 및 연기방출의 위험성이 증가하였다.

In this study, combustion and smoke characteristics according to the aging of class 1E cables in nuclear power plants wereanalyzed through a cone calorimeter test. In the case of combustion characteristics, during the early period, which was thefirst peak of the heat release rate, the peak value of the non-aged cable was higher by approximately 20-50 kW/㎡ than thatof aged cables. However, in the mid-late periods, which was the second peak, the value of the aged cables were higher thanthe non-aged cable due to the decrease in flame retardant performance with aging deterioration. In addition, the duration ofthe char layer of the aged cables was shortened by 200 s than that of the non-aged cables due to the unstable formation ofchar layer. The total heat release measured was approximately 1.4 times higher in the aged cables than in the non-aged cables. In the case of smoke characteristics, the smoke production rate and total smoke release show a similar trend with the heatrelease rate and total heat release. The total smoke release of the aged cables was measured to be higher than that of thenon-aged cables. The tendency of the smoke factor increased with aging deterioration, and the values of the smoke factor inthe aged cables beyond 4 years were approximately 1.76-2.0 times different from those in the non-aged cables. Consequently,the smoke risk increased with aging deterioration. Therefore, the risk of heat and smoke release increased as aging progressed.