Since the beginning of the 90’s, in relation to the French regulatory context evolution that introduces the periodic safety review (PSR) concept), modifications implementation practices have turned to new approaches, introducing the “batching policy” concept.
Following this policy, the batch of VD2 modifications to be implemented on the 1300 MWe series results mainly from the conclusions of the safety studies performed in the framework of VD2‑1300 PSR, initiated in 1997 and enclosed in 2005.
During the examination of the safety studies performed in the framework of VD2 PSR related to the 1300 MWe series, IRSN suggested that EDF would:
· complete the demonstration of the performance of the proposed modification aiming at improving the containment pressure reducing strategy applied to total loss of heat sink at cold shutdown states when the reactor vessel is opened,
· propose new modifications concerning internal explosions and spurious orders from the automatic monitoring and control device.
Finally, 45 modifications resulting from PSR or specific safety studies performed in the frame of PSR, which represent 75% of the global set of safety-significance modifications, will be set during the VD2 outages. The VD2 batch of modifications has been implemented on the lead unit in April 2005 and its implementation will continue over 9 years for the whole units of this series.
For the modifications of major safety significance, for which design principles may introduce either new risks on the safety demonstration or new technologies, IRSN has checked, before implementation, that there was no potential safety regression risk.
For other modifications, in case some potential safety risk exists during implementation or operation and requires requalification criteria validation or efficiency validation, experience feedback is analyzed before generalization.
At the end of this year, IRSN will finalize its examination.