Office for Nuclear Regulation

Heysham 1 – Inspection ID: 52289

Executive summary

Date(s) of inspection:

May 2023

Aim of inspection

This was a planned inspection of EDF Energy Nuclear Generation Ltd.’s (NGL’s) Heysham 1 Power Station, undertaken as part of the planned intervention strategy for the Operating Facilities Division (OFD) of the Office for Nuclear Regulation (ONR). The work was be carried out in accord with the planned inspection programme contained in the Heysham 1 Integrated Intervention Strategy (IIS) for 2023/24.

The purpose of this intervention was to gain confidence that the licensee’s current Licence Conditions (LC 17) management system, chemistry engineering and COMAH arrangements associated with chemistry commodity purchase, delivery, storage and connection to plant are adequately implemented, effective and integrated.

Subject(s) of inspection

  • COMAH – Control of Major Accident Hazards Regulations 2015 – Rating: GREEN
  • LC 17 – Management systems – Rating: GREEN

Key findings, inspector’s opinions and reasons for judgement made

The Office for Nuclear Regulation (ONR) conducted a Licence Condition 17 (LC17) -Management Systems inspection into the arrangements for chemical commodities at Heysham 1 power station (HY1). The inspection also covered arrangements in place to comply with the Control of Major Accident Hazards 2015 Regulations (COMAH), conducted on behalf of the Competent Authority (CA) and focused on the control of chemical commodities in preventing major accidents.

The inspection was part of the annual intervention programme agreed with HY1. Remote engagements were carried out in advance in preparation for the site visit.

The inspection sampled 3 commodities: Boric Acid, Sodium Hypochlorite and Hydrazine. The key regulatory activities undertaken were:

  • Review of LC17 arrangements for chemical commodities
  • Review of the Major Accident Prevention Policy and arrangements for incompatible mixing emergency scenarios
  • Site inspection of chemical commodities being sampled
  • Observation of the delivery and offloading of sodium hypochlorite

Regulatory judgment was based on determining compliance with LC17 and COMAH 2015 including the associated guidance L111.

An inspection rating of GREEN was assigned to both the LC17 and COMAH parts of the intervention. Observations and advice given by inspectors was positively received by HY1. Required improvements to the demonstration of measures taken to prevent major accidents, as required under COMAH 2015, are captured in RI-11563.


Licence Condition 17 – Management Systems

At the outset of the inspection, I noted that the development of arrangements was within the auspices of the corporate technical oversight (CTO) function. I therefore maintain several queries with respect to production of arrangements, which I intend to follow-up with the CTO function. My sample was therefore focused upon the implementation of LC17 arrangements.

With regard to implementation of LC17 arrangements, I targeted boric acid, sodium hypochlorite and hydrazine. Based on my sample, I was content with HY1 arrangements within operating instructions. Specifically, I welcomed the recent CTO QA grade review of chemical commodities, including actions to implement sampling of boric acid. Similarly, I encouraged HY1 to embrace further engineered protections for sodium hypochlorite as these were developed across the supply chain.

Based on my sample, I was content with HY1 implementation of management system arrangements with respect to chemical commodities. I therefore judge a rating of GREEN to be appropriate for LC 17 at HY1.


Based on the sample of chemical commodities across the two-day inspection, I judged that arrangements on site for control of chemical deliveries and associated offloading and storage of chemical commodities are adequate and meet the required standard. Procedural controls were adhered to and demonstrated effective control of the risks associated with delivery and handling of dangerous substances.

The requirement for a Major Accident Prevention Policy (MAPP) is under Regulation 7 of COMAH, the accompanying guidance to these regulations, L111, details the expectations for the content of and its implementation via a safety management system (SMS). The dutyholder’s demonstration of their arrangements for controlling the risk of a major accident, via MAPP, was not fully demonstrated. The MAPP did not fully address all credible major accident scenarios. I have raised a Level 4 regulatory issue to ensure all measures necessary are taken to support the upskilling of individual stations in the COMAH compliance discipline and to track the revision of the MAPP which is due now (see RI-11563).

Regulation 7 of COMAH states that the MAPP should contain details about the range of emergencies envisaged and the arrangements in place for dealing with them. I identified a shortfall in the emergency arrangements for a chlorine generation scenario. HY1 agreed to review and update their emergency response handbook. This will be captured as an action within the Level 4 regulatory issue.

An inspection rating of GREEN has been assigned to the COMAH aspects of this intervention with minor improvements required captured in the level 4 regulatory issue.