The restart was planned for 25 May but had to be postponed somewhat due some extra work on the reactor vessel.

During the regular overhaul, which was scheduled to take 40 days, all maintenance works and testing were successfully carried out by a 1,500-member team, according to NEK.

Among the most challenging tasks was the replacing of the reactor head and the rotor of the main generator.

A third back-up diesel generator was also installed.

Since its last scheduled maintenance in November 2010 Krško has generated 8.5 million megawatt hours of electricity, slightly below plans.

Krško, jointly owned by Slovenia and Croatia, is the most important power plant in Slovenia, meeting about a third of Slovenia's energy needs while exporting half of its production to Croatia.