Office for Nuclear Regulation

Dounreay – Inspection ID: 22-011

  • Site: Dounreay
  • IR number: 22-011
  • Date: April 2022
  • LC numbers: 8, 10, 12, 23, 24, 28

Executive summary

Purpose of Intervention

This intervention, conducted at Dounreay Site Restoration Limited (DSRL), was undertaken in accordance with the 2021/22 Integrated Intervention Strategy (IIS) for Dounreay (note – this intervention was originally scheduled to be undertaken in December 2021), 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 (NLS)) is focussed on the implementation of criticality safety on the sampled sites.

Interventions Carried Out by ONR

The inspection was conducted via a walk-down of one of the DSRL operational facilities (D2160), by discussions with key plant personnel and by examining the licensee’s criticality safety documentation, training records, maintenance schedules / records and on-site signage (e.g. criticality notices, evacuation routes). The following Licence Conditions (LC) were therefore the focus of the intervention:

  • LC8 – Warning notices.
  • LC10 – Training
  • LC12 – Duly authorised and other suitably qualified and experienced persons.
  • LC23 – Operating rules.
  • LC24 – Operating instructions.
  • LC28 – Examination, inspection, maintenance and testing.

Explanation of Judgement if Safety System Not Judged to be Adequate


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

We are satisfied that DSRL’s arrangements for ‘Criticality’ warning signs and their implementation meet the requirements of LC8 and the relevant good practice within ONR’s NS-INSP-GD-008. . In particular, DSRL’s process for inspecting warning notices (‘Safety Signs Survey Report’) is made against the extant regulations, and the criticality safety specific evacuation route signage and warning lights are included on the maintenance schedule as evidenced by inspection of their most recent ‘Preventive Maintenance Work Order’s.

We are satisfied that DSRL’s arrangements for the training and provision of suitably qualified and experienced personnel with criticality safety accountabilities and their implementation, meet the requirements of LC10 and LC12, and the relevant good practice within ONR’s NS-INSP-GD-010 and NS-INSP-GD-012. In particular the areas of competence defined for Criticality Safety Assessors were in broad agreement with those defined within the ‘Working Party on Criticality (WPC) Criticality Competence Framework’.

The training records we inspected, with respect to criticality safety training, for plant access were current and in date, and the training portfolio we inspected for a Criticality Specialist Trainee was found to be detailed and comprehensive. It was found however that some of this detail was absent from the criticality safety ‘Guidance Note’; a Regulatory Issue has been  raised to monitor DSRL’s progress in addressing this minor shortfall.

We are satisfied that DSRL’s arrangements for the identification of criticality safety limits and conditions and their implementation within operating instructions meet the requirements of LC23 and LC24 and the relevant good practice within ONR’s NS-INSP-GD-023 and NS-INSP-GD- 024. In particular, a clear link was found from the derivation of ‘Limits and Conditions’ within the Criticality Safety Assessment (CSA) through to the plant documentation and point of work documentation (Operating Instructions and Criticality Clearance Certificates). DSRL use a tiered approach to derivation of ‘Limits and Conditions’, in agreement with the ONR Technical Assessment Guide (TAG) for ‘Limits and Conditions for Nuclear Safety’.

The ‘Quality Assurance’ process for issuing a CSA was found to include steps where the relevant plant reviews the CSA for accuracy and ease of implementation of the ‘Limits and Conditions’ derived. However, DSRL could not supply evidence of where this process is recorded; a Regulatory Issue has been  raised to monitor DSRL’s progress in addressing this minor shortfall.

We are satisfied that DSRL’s arrangements for the examination, inspection, maintenance and testing of safety systems necessary for criticality safety and their implementation meet the requirements of LC28 and the relevant good practice in ONR’s NS-INSP-GD-028. In particular, items of plant that may affect safety are included on a maintenance schedule, from which applicable ‘Preventive Maintenance Work Orders’ are scheduled. An example of one of these, for maintenance of the Criticality Incident Detection System (CIDAS) was inspected and found to have the necessary maintenance carried out and authorised.

Conclusion of Intervention

Overall, we consider that DSRL has implemented adequate arrangements to meet the requirements of the legislation covered by this intervention in those areas inspected. We did not identify any matter impacting on nuclear safety that required any further immediate regulatory action.