A safety assessment by the UK’s independent nuclear safety regulator, the Office for Nuclear Regulation (ONR) of submissions made by EDF Energy, has confirmed that the pressurised water reactor (PWR) at Sizewell B does not have the defects identified in two Belgian PWRs and measures are in place to ensure similar defects would not occur at the proposed Hinkley Point C.
EDF Energy welcomes the ONR assessment which concluded that the precautions taken during the manufacture of the reactor pressure vessel for Sizewell B has minimised the likelihood of similar defects to those in Belgium occurring at Sizewell B and that if any defects of the type seen at Doel 3 and Tihange 2 had occurred, these would have been detected and recorded. The ONR also concluded that inspection techniques and procedures applied for the proposed Hinkley Point C are adequate to detect and report defects of the type reported at the plants in Belgium.
Sizewell B submitted the results of its safety review to the ONR justifying that it is safe to continue operating following the defects found in the Belgian PWRs Doel 3 & Tihange 2. EDF Energy’s new nuclear build team, working on the Hinkley Point C twin PWR project, also satisfied the regulator that the approach it is taking during the manufacture and inspection of its forgings will ensure that similar defects would not occur at Hinkley Point C.
In July 2012 routine safety inspections of Doel 3 identified a large number of small defect indications in the reactor pressure vessel (RPV). As a precautionary measure a safety review was instigated at Sizewell B, the only PWR in the UK and also a review and comparison of the learning arising against the approach being taken for the manufacture and inspection of the Hinkley Point C forgings.
The robust safety review of Sizewell B confirmed that –
- Advanced steel making processes have meant that no flaws of the kind seen at Doel 3 were present at the time of manufacture
- Ultrasonic tests which would have detected defects in the pressure vessel similar to those found at Doel 3 were conducted and independently validated following manufacture, during pre-service inspections and through routine in-service inspections at the station
- The detailed review of the Sizewell B vessel lifetime records confirm that the Reactor Pressure Vessel was manufactured and inspected to a very high quality. There is therefore no evidence from the Doel 3 operational experience that changes the risk analysis already presented in the Sizewell B safety case.
The HPC review confirmed:
- The additional requirements in specification and tight controls in manufacturing ensure the risks of this type of defect indication occurring are kept very low.
- Our extensive regime of factory inspections will provide the highest level of confidence that the controls in manufacturing are effective.
Furthermore, the twenty year inspection of the Reactor Pressure Vessel at Sizewell B which is due to take place in Spring 2016, will include re-inspection of the main welds in the Reactor Pressure Vessel and some sections of forging material. These inspections will use the same techniques as those deployed at the ten year inspection in 2005 and which have been demonstrated to be sufficiently sensitive.