Following an extended scheduled outage, the operating power was being gradually increased until the reactor was stopped just before 5 AM this morning at the output of 90% by the new measuring system of the reactor coolant, which was one of 30 modifications introduced in the month-and-a-half remount.

According to NEK, the power plant is stable and all the parameters were at normal values at the time of the shutdown, which was launched by the inappropriate response of the measurement electronics.

Troubleshooting of the measurement system is under way and the plant is expected to be back online by Monday.

After comprehensive improvements were introduced to the reactor after damage had been detected to fuel rods, NEK and was testing the measurement system at different power outputs together with the supplier Westinghouse.

The power plant spent some EUR 4m on the series of preventive measures related to the issue with the fuel rods, including stabilisation of fuel to increase its resistance to vibration caused by circulation of coolant.