The first power unit of the Volgodonsk nuclear...

"The system was activated at 9:20 a.m. Moscow time [6:20 GMT] at the first power unit. A decision was made to reduce its power and bring it to complete stoppage," the spokesman said.

Problems with a steam generator were the likely cause of the protection system activation. Repairs will take about four days, the spokesman said.

The Volgodonsk NPP, situated some 1,000 km (621 miles) south of Moscow and has one pressurized water reactor, started operation in 2001.

ROSTOV-ON-DON, January 10 (RIA Novosti)