In the wake of two earthquakes on12 September, four units at South Korea's Wolsong NPP were shut down the next day by operator Korea Hydro and Nuclear Power Co (KHNP). The earthquakes, of magnitude 5.1 and 5.8, occurred near the city of Gyeongju. South Korea's meteorological agency said the 5.8 magnitude earthquake was the strongest recorded in South Korea. Units 1-4 were taken offline at Wolsong NPP with a combined capacity of 2,779MWe.
KHNP, owned by state-run utility Korea Electric Power Corp (KEPCO), operates 25 nuclear reactors, supplying about one-third of total electricity. South Korea's reactors are designed to withstand a magnitude 6.5 or 7.0 earthquake, according to the Nuclear Safety and Security Commission (NSSC). Orders were given to nuclear operators to upgrade old reactors to that standard after the disaster at Japan's Fukushima Daiichi NPP in 2011. "That will be completed by next year," said NSSC spokeswoman Shim Eun-jung