On 23 August 2012, Reactor 1 of the Uljin (aka Ulchin) nuclear power plant in Korea, south, shut itself down.  Officials with the Korea Hydro & Nuclear Power Company do not know why.

A warning signal went off, but there is no radiation leak, according to officials.  Korean media says the International Atomic Energy Agency (IAEA) is not concerned.

Uljin-1 began operations in 1988 and is a French Framatome (company is now called Areva) type pressurized water reactor (PWR).  The Uljin nuclear plant is considered the 13th largest electricity generating facility in the world, producing nearly 5,900 megawatts.