The Nuclear Safety and Security Commission(NSSC) said on Saturday that two-point-three tons of water from a spent nuclear fuel storage facility at the Wolsong Nuclear Power Plant in Gyeongju, North Gyeongsang Province, has leaked into the sea.

The NSSC said it received a report about the leak at the Wolsong Unit Four reactor from the Korea Hydro Nuclear Power Company(KHNP), the power plant's operator, and immediately dispatched experts from the Korea Institute of Nuclear Safety(KINS) to investigate exactly how much water was leaked and what caused the spill.

KHNP said it took action to stop the leakage at around 4:34 a.m., upon noticing the water level of the storage tank had gone down, and reported the incident to the NSSC by 7:53 a.m.

The operator said that the effective dose of the water leak is estimated to be 0.000000555 mSv/year, well below the dose limit for the general public. 

The NSSC said it would announce the results of its investigations along with an environmental impact assessment.

The Wolsong Unit Four reactor has been shut down under planned maintenance since April 20.