원전용 비상디젤발전기 성능열화에 관한 연구

Abstract

The national electricity power shortage has been serious problem due to continuous increase in power consumption. Consequently, nuclear power plant (NPP) comes into the spotlight as a solution of this problem.

There are 23 units of NPPs in Korea. Gross generation capacity by NPP for 2011 was 154,723 GWh and it takes 31.1% of total gross generation in Korea. 9 units of NPPs are under construction, so NPP is a big part of total gross generation.

By the way, the safety of NPP has been rising as a topic conversation newly due to the Fukushima NPP accident on Mar. 2011 and Gori NPP accident on Feb. 2012.

Especially a lot of concerns on old NPPs have increased. Because the design life of Kori NPP was finished in 2007, and has been extended for 10 years. Recently, the number of NPP more than 30 years are being increased like No.1 Wolseong NPP.

The emergency diesel generator (EDG) in a NPP must be started within 10seconds and supply electrical power to engineered safety features (ESF) within 1 minute if a loss of off-site power (LOOP), or a loss of coolant accident(LOCA), or their combination occurred. Each NPP has an EDG set consisting of two diesel generators for redundancy. In addition to the EDG set, an alternate alternating current diesel generator (AAC DG) is installed and shared by several units to cope with a station black out (SBO), i.e., a loss of the offsite power concurrent with reactor trip and unavailability of the EDG set.

EDG plays an important part in the safety of NPP. Unlike diesel engines in other fields, there are much problems like scuffing on piston-liner and cam, cut-off on crank shaft by excessive torsional vibration, deterioration by high load operation(100-110%) and rapid load-up.

In this study, the feature of EDG at NPP was understood. No.1 & No.2 Younggwang NPP operated for 23 years was selected and the causes of EDG deterioration for old NPP were analyzed. The result of shop test was compared with the test result on Mar. 2009. Through the analysis of the performance, the method to improve the performance and reliability for old NPP was provided.