A nuclear reactor on South Korea’s southeast coast halted operation on Monday as rainwater flooded in, plant operators said.

The Kori-2 nuclear power plant, about 450 kilometers southeast of Seoul, was manually shut down at about 3:54 p.m. No immediate threats of a radiation leak have been detected, according to the Korea Hydro and Nuclear Power Co.

“As excessive water flowed into a building that takes in seawater to cool down turbine steam, we decided to manually halt the operation of the nuclear reactor for the safety of the electrical equipment,” the KHNP said.

Heavy rain pummeled Busan, where the nuclear reactor is located, and its surrounding area on Monday, with rain falling at a maximum rate of 130 millimeters per hour. It is unusual that a nuclear reactor is shut down from heavy rain.

The Kori-2 reactor started its commercial operation in July 1983. (Yonhap)