This intervention report covers activities carried out by ONR inspectors at the Torness power station Reactor 1 2014 outage on the condition of the graphite core. It is normal practice for ONR to carry out an intervention on the various core inspection and sampling activities that are performed at each statutory outage. This is thus an intervention against the requirements of Licence Condition 28.
This intervention report only covers activities relevant to the graphite core dealt with during the course of the ONR inspection. It will be followed by an assessment report that will include judgements made on the Licensee's safety case for returning the reactor to service.
The Licensee, EDF Energy Nuclear Generation Limited has carried out all the established commitments in terms of graphite visual inspection, dimensional measurements and trepanning of samples. At this outage, new equipment has been used (NICIE2) and additionally 16 fuel channels have been inspected, which is twice as many as have been inspected in previous outages. The Licensee deserves credit for having managed this increase. There was one untoward event that involved trepanning at an incorrect height, missing one of the graphite layers that are normally sampled. However the Licensee subsequently trepanned further samples and actually exceeded the commitment.
Two notable cracks were found and such cracking is unusual at Torness. I have examined the images and do not consider that they pose any challenge to the integrity of the graphite core. I will consider this matter further in my forthcoming assessment report. I note here though that such cracks are present in greater numbers at other reactors.
I anticipate that my assessment report will conclude that the findings of the Licensee's inspection activities do not present any challenge to their safety case for the graphite core. I conclude here that the inspections and trepanning were performed to an adequate standard.
The Licensee has carried out the activities that they committed beforehand to perform. They have performed well introducing new equipment and increasing the amount of visual inspection performed over that achieved at earlier statutory outages. Based on my own intervention, I conclude that they have performed the work to an above adequate standard. I propose that an IIS rating of 2 is appropriate.
I recommend that the project inspector considers this report and my forthcoming assessment report in forming his conclusion as to whether to recommend that Consent is granted for return to service. I do not expect the matters that have arisen to do with the graphite core will amount to any reason to prevent that return to service.