The Wolsong CANDU nuclear power plants are owned and operated by the Korea Hydro and Nuclear Power Company (KHNP). The four units at the Wolsong site are 700 MWe class CANDU 6 reactors. Wolsong Unit 1 went into service in 1983 and Wolsong Units 2 and 3 began operation in 1997 and 1998. Wolsong Units 2, 3, and 4 repeat the basic design of Unit 1, with significant design updates and advancements.
Construction began at the Wolsong site in 1977 with the pouring of the reactor building sub-base for Unit 1, which had a 60-month construction period. Construction resumed at the site in 1992, on Wolsong Unit 2, and continued through Units 3 and 4 — to Oct. 1, 1999, when Unit 4 was declared in-service. Several records were set during the work on Units 2, 3 and 4 — the most notable being a 51-1/2 month construction duration for Unit 3 from first containment concrete to in-service.
Units 2, 3 and 4 were designed and constructed using state-of-the-art integrated electronic engineering tools, including Computer Aided Design and Drafting (CADD) systems and Integrated Electrical Control (IntEC) automated wiring, which is a data management software tool for the design and installation of cabling and wiring.
In 2006, KHNP began an extended outage to retube and refurbish the Wolsong 1 reactor, commonly called life extension. During this process all 380 fuel channels and calandria tubes, along with the 760 feeder pipes were replaced, among other maintenance work. The reactor returned to full power on the Korean electrical grid in July 2011, marking the first CANDU 6 reactor to be retubed and restarted.