Bad sensor shuts down reactor at Uljin plant

For the eighth time this year, a reactor at a Korean nuclear power plant has shut down unexpectedly.

Korea Hydro and Nuclear Power Corporation (KHNP) reported that a reactor at the Uljin plant in North Gyeongsang shut down at 2:45 a.m. after a control valve for a steam turbine malfunctioned.

The plant’s operator blamed a sensor on an electric hydraulic control system.

KHNP characterized the problem as minor and said the Uljin plant’s No. 2 reactor could be up and running again as early as today.

“We are currently replacing the faulty part,” said Choi Yong-jin, assistant director of KHNP’s communications team. “As soon as we complete the test run and no problem turns up, the Nuclear Safety and Security Commission will check the report on the test run and allow us to resume operation.”

The KHNP also stressed that the reactor shutdown posed no threat to the safety of plant employees or the general public.

The Uljin No.2 reactor that malfunctioned has been operating since 1989. Before yesterday’s incident, it had unexpectedly shut down 17 times.

However, it had been operating without a problem since it shut down twice in 2007. The reactor has the capacity to generate 950,000 kilowatts per hour.

The Uljin plant on Korea’s east coast has a total of six reactors, of which two are currently unused. The No. 4 reactor has been suspended since December after a tube in the steam generator failed.

It is currently undergoing a complete replacement phase and is not scheduled to resume operations until May.

The No. 6 reactor is also suspended for a monthlong inspection that is expected to be completed by the end of next month.

Korea, the world’s fifth-largest producer of nuclear power, currently operates 23 reactors that supply about 30 percent of total electricity consumption, according to the Korea Nuclear Energy Promotion Agency.

By Lee Sun-min [summerlee@joongang.co.kr]