The Hungarian Atomic Energy Authority gave conditional approval for the restart of Paks 2 on 23 July.
The unit was shut down for refuelling when damage was discovered to 30 VVER fuel assemblies which had been successfully cleaned in service pool number one but had subsequently overheated when coolant flow was insufficient. When the lid of the cleaning tank was lifted and cold water flowed back into the tank the assemblies were damaged to the extent that fuel was able to leak. The incident was rated level 3 on the International Nuclear Event Scale.
TVEL are contracted to remove the damaged assemblies but a precondition of the approval for restart is that the reactor will not be operational while that process is being carried out.
The presence of a reactor operator specifically to monitor service pool one is one condition necessary for the restart. Autonomous control systems for the sevice pool must also be operation before start-up, and start-up procedures must be confirmed step-by-step by an independent expert.
Paks will be allowed to restart the unit as soon as the conditions are met and is expected to do so following a training and testing programme pencilled in for the beginning of August. The unit could be producing power by the end of that month.