Office for Nuclear Regulation

Hunterston A site inspection

Executive summary

Purpose of intervention

This report covers interventions in pursuit of the ONR integrated intervention strategy for Hunterston A, in particular to address regulatory issues identified as part of the inspection plan, and carry out the planned compliance inspections.

Interventions Carried Out by ONR

This report covers interventions at Hunterston A to address licence condition (LC) compliance inspections as follows:

Explanation of Judgement if Safety System Not Judged to be Adequate


Key Findings, Inspector's Opinions and Reasons for Judgements Made

Only the Compliance Inspections and relevant follow-up meetings are included in this executive summary, as all other interventions were for information only.

LC6  The purpose of the intervention was to undertake an inspection of the licensee’s arrangements and implementation under LC6. LC6 requires licensees to keep adequate records to demonstrate their compliance with the conditions attached to their site licence and to maintain these records for 30 years unless ONR approves some other period.

The site arrangements against LC6 were found to be adequate and while tarnished by significant IT problems during the inspection, the implementation of those arrangements was also found to be adequate.  I consider that an IIS rating of 3 (adequate) is appropriate.

LC23  The purpose of this intervention was to undertake an inspection of the licensee’s arrangements and implementation under LC23.  LC23 requires licensees to identify conditions and limits necessary in the interests of safety, and carry out operations in compliance with those conditions and limits, known as operating rules.

Site have a single approved operating rule that was sampled for this intervention but it was noted that a significant number of safety measures and safety assumptions are in use across the site and on review ONR confirmed that these were lower-tier operating rules for regulatory purposes, noting only that site and regulator terminology did not align.

The single approved operating rule relates to the permissible concentration of hydrogen in air in the exhaust from a waste bunker and was judged against the expectations given in the approved code of practice (ACOP) for the Dangerous Substances and Explosive Atmospheres Regulations 2002 (DSEAR).  Site was unable to explain satisfactorily why the values did not align with those given in the ACOP and further were not able to provide an appropriate justification for the choice of value.  Alarm and action levels were significantly below the value cited in the operating rule and there was no evidence of any excursion above background levels of hydrogen, but the rule is expected to align with the relevant good practice in this area.  The lower tier operating rules defined by site as safety assumptions were sampled and found to not met the entirety of ONR guidance.  In light of these non-compliances with relevant good practise in the form of an approved code of practice and ONR guidance, I considered an IIS rating of 4 (below standard) was appropriate.

LC24  The purpose of this intervention was to undertake an inspection of the licensee’s arrangements and implementation under LC24.  LC24 requires licensees to carry out operations that might affect safety in accordance with written instructions (”Operating Instructions”), and that those instructions should implement any operating rules that might be relevant. 

Inspecting against LC24, the arrangements in the Solid Active Waste Bunker Recovery (SAWBR) control room were sampled and a number of observations and areas for improvement identified. The inspection also identified an uncontrolled amendment to an operating instruction located at the point of work. On this occasion the nature of the amendment was confirmed to be benign, but there is no scope for complacency regarding uncontrolled document amendments and this led to an IIS rating of 4 (below standard) being appropriate.

Conclusion of Intervention

No major shortfalls were identified during this inspection, however there were shortcomings identified against two of the three areas sampled and these led to ratings of below standard in those areas.  A letter will be sent to site to communicate the actions required to remedy the shortcomings against LC23 and LC24, and also list the other observations and areas for improvement identified.  These matters will be raised on the ONR issues database and the Hunterston A nominated site inspector will follow up as part of normal business.