The Hanbit Nuclear Reactor 6, located in Yeonggwang, South Jeolla Province, suddenly halted operations on Wednesday afternoon due to mechanical failure, adding to the concerns on electricity shortage.

“The reactor suddenly went out of order and had to be suspended at 2:44 p.m.,” said an official of the Korea Hydro & Nuclear Power Corporation.

As a result, the nation’s backup power level dropped from the 4.5 million kilowatt level to 3.7 million kilowatts as of 3 p.m., which triggered the phase 3 alarm, according to the Korea Power Exchange.

A faulty steam valve was reported to be the cause of the reactor breakdown.

The breakdown comes amid reports that the government is preparing for a possible blackout in September when many of the nation’s nuclear reactors will have to be temporarily shut down for maintenance reasons.

The weather is expected to get cooler, but the Trade Ministry, which has been issuing a series of warnings against power outages, said it will stay on guard.

By Bae Hyun-jung (tellme@heraldcorp.com)