The purpose of this intervention, carried out on 6th September 2019, was to undertake a reactive unplanned intervention at the Wood office in Knutsford. During periodic shutdowns, Wood is contracted by EDF Energy Nuclear Generation Ltd (NGL) to review the video footage from the graphite core inspections and produces inspection sheets summarising the findings from the graphite inspections. The inspection sheets are reviewed, defects are sentenced according to a defined process and are subsequently endorsed by the Graphite Assessment Panel (GAP). The GAP is composed from graphite specialists from NGL and from Wood. The findings from the GAP sheets are then assessed against the assumptions in the safety case before the reactor can be returned to service.
This intervention at Wood’s offices was conducted following the observation of a circumferential defect in control rod channel 2Q22, Layer 10, during the Hartlepool (HRA) Reactor 2 (R2) periodic shutdown. Since the quality of the images reported in the inspection sheet did not allow for a conclusive assessment of the defect, three ONR graphite specialists carried out a reactive unplanned intervention at Wood.
NGL assisted in organising this intervention. So, while NGL did not attend this inspection, I was assessing NGL’s management of the supply chain to deliver services to facilitate NGL’s compliance with LC28.
The objective of this intervention was therefore:
(i) to assess the quality of the video footage for control rod channel 2Q22 taken during the Hartlepool Reactor 2 periodic shutdown and;
(ii) to determine the nature of the defect observed in Layer 10 of control rod channel 2Q22 during the periodic shutdown.
Two ONR inspectors and I carried out an intervention at Wood, Knutsford, the activities undertaken were as follows:
In my opinion,
I consider that Wood representative’s identification of the defect, informing the licensee (NGL), and sentencing of the defect to prompt discussion at the GAP is appropriate and demonstrates a good questioning attitude.
From the video footage I observed, the defect appears to be consistent with other machining marks of limited depth. No crack-like feature appears to be present from the footage. The video footage taken during commissioning indicates that the defect was likely to have been present at the time of construction. Hence, I am content that the defect observed in control rod channel 2Q22 is likely to have been caused by machining during the manufacture of the brick.
It is my opinion that a 360° scan of the defect (as performed for other similar observations) would have improved the sentencing of this defect. I will consider the adequacy of the inspection procedure in more detail in my assessment report for the return to service of the reactor following the periodic shutdown. However, I consider that the video provides images of sufficient quality for the defect on 2Q22 to have been adequately sentenced by the GAP.
Based on the findings of this intervention, I have allocated an overall ONR rating for this inspection of ‘GREEN’– No Formal Action.