Office for Nuclear Regulation

Dounreay – Inspection ID: 52089

Executive summary

Date(s) of inspection:

  • February 2023

Aim of inspection

The aim of the inspection was to consider DSRL’s implemented measures to prevent, control and mitigate fire hazards affecting nuclear safety in the Prototype Fast Reactor (PFR) facility (including irradiated fuel caves). This will included reviewing DSRL’s examination of fires and their impact on items important to safety which should be protected to achieve the safety objectives.

Subject(s) of inspection

  • LC 10 – Training – rating: Green
  • LC 23 – Operating rules – rating: Green
  • LC 24 – Operating instructions – rating: Green
  • LC 27 – Safety mechanisms, devices and circuits – rating: Green
  • LC 28 – Examination, inspection, maintenance and testing – rating: Green

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

The purpose of this intervention was to ensure that Dounreay Site Restoration Ltd (DSRL) is complying with the requirements of their nuclear site license specifically those conditions related to nuclear fire safety.

This intervention was a themed inspection which covered aspects of nuclear fire safety. However, DSRL’s implementation of arrangements related to the following license conditions were explicitly sampled and are therefore provided with a Red, Amber, Green (RAG) rating. Compliance was assessed using the relevant ONR inspection guidance, specifically:

  • NS-INSP-GD-0010 (Training)
  • NS-INSP-GD-0023 (Operating Rules)
  • NS-INSP-GD-0024 (Operating Instructions)
  • NS-INSP-GD-0027 (Safety, Mechanisms, Devices and Circuits)
  • NS-INSP-GD-0028 (Examination, Inspection, Maintenance and Testing)

The inspection consisted of examination of the licensee’s arrangements regarding nuclear fire safety for the Prototype Fast Reactor (PFR) complex, meetings to assess the implementation and management of nuclear fire safety topics at a site and facility level and a walkdown of key areas of the PFR complex.

This intervention was undertaken by two inspectors from the Office for Nuclear Regulation’s (ONR) Nuclear Internal Hazards & Site Safety (NIHSS) specialism and the Dounreay site’s Nominated Site Inspectors.

During review of DSRL’s maintenance records associated with the PFR Fire Alarm & Detection System (FADS) it was noted that the trail of evidence for inspection, testing and maintenance for the system was incomplete. This included incomplete transcription of recorded defects between inspection work orders and raised maintenance work orders, which meant that it was not clear if all defects identified had been repaired. There was also ambiguity in the method of recording defects (question marks noted as the test outcome) and modifications to procedures in red pen (drawing references) had not been carried forward in the method updates. This could lead to a misrepresentation of the condition of the FADS. A Level 4 Regulatory Issue has therefore been raised to monitor Quality Assurance (QA) activities undertaken to bring current records up to an adequate standard and ensure the current processes are suitable to maintain those standards


The following points which form my overall judgement are based on the facts established as part of the inspection, discussions with the nominated site inspectors and my own judgement on the presentations and information provided by the licensee.

  1. The PFR facility is currently in the advanced stages of decommissioning and is undertaking major projects related to the treatment of the remaining sodium and NaK inventory which is largely limited to residues held in pipes, vessels and the reactor vessel.
  2. A Deterministic Fire Risk Assessment (DFRA) has been produced for the PFR as part of compliance with LC15 arrangements.
  3. Only the FADS is recorded in the facility safety case as provided a nuclear safety function and this is linked to personnel evacuation only.
  4. The FADS provides device level resolution within the PFR complex, and this allows Dounreay Fire and Rescue Service to clearly anticipate where a fire may be present.
  5. Maintenance, inspection and testing regimes are in place and no faults on the FADS were observed on the inspection days.
  6. The maintenance records provided to ONR did not form a complete evidence trail of defect identification and subsequent close out.
  7. Evidence of staff competency with respect to the inspection and maintenance of the FADS was available and found to be adequate.
  8. DSRL have limited discharge routes linked to fire scenarios within the PFR complex and waste plans and control procedures are in place to articulate appropriate waste routes to staff.
  9. Some minor shortfalls in the control of combustibles were observed during the plant walkdown however, these were rectified prior to ONR leaving the site.

With regards to the above facts, I consider that the site is complying with the licence conditions inspected within the context of nuclear fire safety. I therefore judge that an ONR Inspection Rating of Green is appropriate for each license condition inspected.