South Korea's Hanul No.1 reactor shut after technical problem - operator
"There has been no radiation leak and the power generating station is in a stable condition," the statement said.
The 950-megawatt Hanul No.1 reactor is located in the county of Uljin, over 200 km (124.27 miles) southeast of Seoul.
The company, fully owned by utility Korea Electric Power Corp, runs 25 reactors including one at the test run. Nuclear power generation accounts for a third of South Korea's electricity.
(Reporting by Rebecca Jang; Editing by Anand Basu)