The purpose of this intervention was to conduct a benchmark inspection of the arrangements in place at Hinkley Point B power station to manage the integrity of concealed pipework, with an emphasis placed upon how corrosion is managed. The work was carried out as part of the planned intervention task sheet TS015 - "Pipework - Material Condition - Corrosion Under Insulation and Concealed/Buried Systems".
I carried out this inspection accompanied by an ONR Project Inspector. The inspection took place on 24 and 25 May 2016 and involved discussions with a number of EDF Nuclear Generation's (NGL) employees responsible for the operation and safety of the plant. We also undertook plant walk downs.
The objective of the inspection was to obtain information relating to NGL's arrangements for managing corrosion of its concealed pipework, in order to identify any areas of positive operational experience, or shortfalls to our expectations. I concentrated my intervention on items I judged important to nuclear safety, focussed upon Structural Integrity.
The inspection reviewed the procedures, roles and responsibilities of key staff and sampled compliance arrangements against Licence Conditions (LC)10 (training) and LC28 (examination, maintenance, inspection and testing) to judge the adequacy of the arrangements in place.
Although areas for improvement have been identified, it is acknowledged that NGL is introducing measures to address them. We judged that the arrangements and their implementation, associated with concealed pipework and corrosion under insulation currently conform to a green rating, but recommend further monitoring once the revised processes have been adopted by Hinkley Point B.
Hinkley Point B was generally able to demonstrate that a process exists to establish the integrity of concealed pipework, particularly relating to external corrosion and corrosion under insulation. The station recognises that the current process is focussed upon inspecting pipework falling under the scope of the Pressure Systems Safety Regulations (PSSR) and it is revising its procedures to include all significant pipework at risk from corrosion.
Hinkley Point B has allocated a Corrosion and Ageing management Co-ordinator as required within Company Technical Specification, "Corrosion and Ageing Management" (CTS031). The Corrosion Co-ordinator has been in post for a relatively short while, but demonstrated a reasonable knowledge of corrosion issues and an awareness of the responsibilities allocated to him within CTS031; he also stated that he had sufficient time and recourse to conduct his duties in the role. My expectation is that his knowledge will develop with time in the post, along with support from suitably qualified and experienced staff at Hinkley Point B and Barnwood.
Having discussed the corrosion awareness training provided at Hinkley Point B, I consider that their approach is generally consistent with those used at the stations visited as part of ONR's phase 1 Corrosion Under Insulation (CUI) visits. The training completed by the System Engineers has resulted in a greater awareness of corrosion issues for concealed systems and CUI in particular, along with production of improved plant walk down reports, containing greater detail.
Generally for the systems sampled during my visit, the station demonstrated that pipework with LC28 significance is included within the Maintenance Schedule (MS). It acknowledged that the MS for a number of systems may need to be revised as the new process of corrosion management is established and implemented.
For the areas visited during the plant tour, I was encouraged that Hinkley Point B could demonstrate progress with planned concealed pipework inspections. Station staff were able to explain how inspection results are assessed degradation sentenced, but it did not appear to be an embedded and documented routine. This is acknowledged by the station and plans to manage the integrity of concealed pipework are being developed.
The cladding in the region of B/G/3865 exhibited several leading indicators for potential susceptibility of the underlying pipework to CUI, along with a lack of awareness by HPB relating to materials of construction; however the section had not been identified for examination by Hinkley Point B or the Competent Person. Following my questions asked during and post visit, the station has inspected the section of pipework and confirmed that it is fit for purpose.
I remain concerned that this example gives the impression that the station does not fully understand the condition of the CO2 pipework. This raises questions over the effectiveness of its process for identifying susceptible areas of concealed pipework for inspection. I intend to inform the station of this concern and will discuss the example in the forthcoming Level 4 meeting at Barnwood. In addition, an action has been placed on Hinkley Point B to provide an inspection and remediation plan for the CO2 system covering the next 18 months. This was generated from issues with potential unknown pipework material and the reference in past assessment reports that sections of pipework are suitable until 2016.
Although areas for improvement have been identified, it is acknowledged that the station is introducing measures to address them. We judged that the arrangements and their implementation, associated with concealed pipework and corrosion under insulation currently conform to a green rating.
The station was generally able to demonstrate that a process exists to establish the integrity of concealed pipework, particularly relating to external corrosion and corrosion under insulation. It recognises that the current process is focussed upon inspecting pipework falling under the scope of PSSR.
PSSR compliance alone may not be sufficient for their pipework to demonstrate compliance with the requirements of LC28, so Hinkley Point B is revising its procedures to include all significant pipework at risk from corrosion. It is therefore recommended that ONR revisit the station at a suitable future date once the revised processes have been implemented, to review and monitor progress.
A list of key findings and actions from this intervention has been provided to the station for its consideration and resolution. One category 4 issue number 4511 has been raised to track the progression of the actions raised during the visit and to prompt a revisit to the site at a suitable future date.