- Site: Hunterston B
- IR number: 21-063
- Date: August 2021
- LC numbers: 8, 10, 12, 23, 24, 28
Executive summary
Purpose of Intervention
This intervention, conducted at Hunterston B (HNB) Nuclear Power Station nuclear licensed site, was undertaken as part of a series of planned cross-site criticality inspections performed by the Office for Nuclear Regulation (ONR). The overall intervention (i.e., across a number of UK nuclear licensed sites) is focussed on the implementation of criticality safety on the sampled sites and has three main aims:
- To identify any deficiencies in licensee’s management of criticality safety (and/or any legal non-compliances) and to work with licensees to ensure prompt and sustained rectification of the deficiencies;
- To identify areas of good practice across the licensees sampled and to share these across UK industry, as a vehicle for enhancing criticality safety across licensees; and
- To drive improvements in licensee’s management of criticality safety and to highlight and action areas where ONR’s own guidance on criticality safety can be improved (e.g., the criticality Technical Inspection Guide (TIG)).
To provide a consistent structure across each of the individual criticality inspections, it was convenient to conduct the inspection against a number of Licence Conditions (LCs) which were judged to have a relevance to criticality safety i.e., LC 8 “Warning Notices”, LC 10 – “Training”, LC 12 - “Duly Authorised and Other Suitably Qualified and Experienced Persons”, LC 23 – “Operating Rules”, LC 24 –“Operating Instructions” and LC 28 – “Examination, Inspection, Maintenance and Testing”.
Interventions Carried Out by ONR
On 10 and 11 August 2021, ONR criticality specialist inspectors, accompanied by ONR’s nominated site inspector for HNB, conducted a planned criticality inspection of the HNB Nuclear Power Station nuclear licensed site. The intervention was conducted by a walkdown of the station’s fuel route, by discussions with key plant personnel and by sampling the licensee’s criticality safety documentation, training records, maintenance schedules / records and on-site signage (e.g., criticality notices).
The intervention was conducted against ONR’s TIG on criticality safety NS-INSP-GD-053 Rev. 6.
Explanation of Judgement if Safety System Not Judged to be Adequate
Not applicable.
Key Findings, Inspector's Opinions and Reasons for Judgements Made
The key findings against each LC are recorded below.
LC 8 (Warning Notices) – Rating = Green
Signage on plant (including criticality notices and other safety signage, e.g., fire signage) was inspected during the plant walkdown and appeared to be in an adequate condition. Criticality Safety Notices (CSN) were legible and easy to understand. In most cases the CSNs were kept within locked glass cabinets to prevent damage and operational graffiti. The ONR inspectors considered this to be an example of good practice.
Evidence was provided demonstrating that the CSNs are subject to three-monthly audits, where every CSN posted on site is checked for accuracy, legibility and issue number, which the inspectors considered is good practice.
There were some instances observed of incorrect and outdated criticality-related fire signage, although these were located in the ‘new fuel’ areas of the plant which will become disused and fuel-free in the near future, due to HNB moving fully to defueling by circa early 2022. Accordingly, these findings are recorded as ‘observations’.
During the plant walkdown it was also observed that there are a large number of ‘defect tags’ (used to indicate a reported defect) posted on various equipment items that in some cases had been present on site for some time. ONR noted that rectification of defects will become important in high usage areas of the plant (such as the ponds) as the plant moves into defuel. The licensee committed to reviewing these defect tags.
We were satisfied with the licensee’s arrangements for warning notices and therefore judged that the overall inspection against this LC merited a rating of ‘Green’.
LC 10 and LC 12 – Training and Duly Authorised and Other Suitably Qualified and Experienced Persons – Rating = Green
Criticality safety training practices were reviewed and found to be of a good standard. There has and continues to be a significant involvement by the central criticality group at Barnwood in the development and delivery of criticality training. All workers on site are required to have a basic awareness of criticality safety in order to be permitted to access the site and workers who have access to the Reactor Controlled Area (RCA) must complete more detailed criticality safety training which is refreshed every three years.
EDF mandates that each station shall train and appoint two criticality safety specialists (HNB have five appointed with good evidence of appropriate succession planning). Criticality specialists receive more detailed training (which again is refreshed every three years) that allows them to be a point of contact on plant for criticality safety advice. The training has previously been sampled by ONR and found to be of a good standard.
We were satisfied with the licensee’s arrangements for criticality safety training and therefore judged that the overall inspection against this LC merited a rating of ‘Green’.
LC 23 and LC 24 – Operating Rules and Operating Instructions– Rating = Green
Criticality safety documentation was sampled. The Criticality Safety Certificates (CSCs – the more detailed document summarised by the on-plant CSNs) were clear to read and understand, with restrictions placed on measurable quantities (e.g., number of packages), making it easy for operators to demonstrate compliance. There was a clear link between the operating rules derived in the criticality assessments and operating instructions on the certificates. We also sampled control of changes to the criticality safety documentation on the plant (e.g., due to plant modifications) and were content that this is adequately controlled.
However, during the plant walkdown we encountered outdated operational documents (including documents relating to criticality safety) in an unlocked drawer in the new fuel inspection area. HNB staff were made aware of this and agreed to address the finding.
From our sample we were satisfied with the licensee’s arrangements for operating rules and operating instructions, and therefore judged that the overall inspection against these two LCs merited a rating of ‘Green’.
LC 28 – Examination, Inspection, Maintenance and Testing (EIMT) – Rating = Green
Maintenance schedules and instructions and completed job cards were randomly sampled for a number of pieces of plant of relevance to criticality safety (e.g., equipment used to handle the reactor fuel or pond boron level sampling). The sampled documents were found to be well written, in date and appropriately authorised. There were clear links between the maintenance schedules and the job cards.
EDF has a fleet-wide online system for searching for maintenance information, which includes job card history; this system seemed easy to navigate. There were some minor clarity issues with some job card documents where some steps of the maintenance instructions were stated as ‘not done’ or ‘not applicable’ with no subsequent explanation, although these were minor points and HNB staff stated they will provide clarifying statements in future. It is worth noting that maintenance schedules were recently improved by the licensee in response to a separate ONR inspection focussed on this topic.
We were satisfied with the licensee’s arrangements for EIMT and therefore judged that the overall inspection against this LC merited a rating of ‘Green’.