A nuclear reactor at the country's Shin Wolseong power plant stopped operations early Tuesday with no immediate risk of radiation leak, plant operators said.

The 1-million-kilowatt reactor stopped operating at 7:44 a.m., according to the Korea Hydro and Nuclear Power Co. The problem has yet to be identified, but company officials said the reactor was in stable condition with no dangers of a radiation leak.

The reactor, located some 400 kilometers southeast of Seoul, began commercial operation in July 2012.

With the temporary shutdown of the Shin Wolseong reactor, the country's power reserve level dropped to less than 4.5 million kilowatts, forcing the state-run power service provider, Korea Electric Power Corp., to issue a preliminary power shortage warning as of 8:35 a.m.

A preliminary warning is elevated to an actual warning once the reserve level drops below 4 million kilowatts.

The country currently operates 23 nuclear reactors that generate about 30 percent of its total electricity consumption.

However, five reactors are currently undergoing scheduled maintenance with two others also recently shut down due to technical problems. (Yonhap News)