Office for Nuclear Regulation

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Inspection of Licence Condition 15 (periodic review of safety cases) in the Waste Treatment Complex (WTC) on Sellafield Ltd.’s nuclear licensed site at Sellafield, Cumbria

Executive summary

Purpose of intervention

This intervention is part of ONR’s programme of inspections of Sellafield Ltd.’s Periodic Safety Reviews (PSR) and specifically considered the Waste Treatment Complex (WTC) Long Term Periodic Review (LTPR). The facility is operated by Sellafield Ltd. (SL) as the licensee. Prior to the inspection, I had decided that SL had already correctly assessed as being very low frequency events, those faults that could result in off-site consequences and, hence, this intervention focused on those faults with the potential to affect on-site personnel, e.g. those involved in operational activities.

Intervention Carried Out by ONR

This planned inspection examined compliance with Licence Condition (LC) 15 (the requirement to undertake Periodic Safety Reviews of the safety case). I followed the lines of enquiry recommended in the ONR fault studies scoping report and agreed during discussions with the inspection team prior to the visit to site. The intervention focused on SL’s review of the safety case in respect of a high impact fault sequence with large operator dose consequences.

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

This was an effective intervention and greatly benefitted from open dialogue and good cooperation between all parties. The inspection determined that SL had undertaken an effective, pragmatic LTPR which has resulted in the licensee identifying 23 potential safety improvements. SL is also planning to implement revised Hazard Analyses (HAZANs) under a new safety case which will allow SL to process predicted future, revised waste inventories.

Our inspection did not reveal any matters of substantive concern that had not already been identified by the licensee in its own review. The inspection did, however, identify three areas which SL should resolve and document when its Confirmation of Safety Letter (COSL) is submitted to ONR later this year:

The status of the recommended improvements, including secondary ones, contained in the revised Design Assessment Report (DARs) and HAZANs.

The identification of the responsible person for delivering any outstanding improvements and how these will be tracked and addressed.

The description of how the revised safety case will be implemented, including training arrangements, particularly with respect to any revised Operating Rules and the operation on the air in-bleed ventilation system.

Conclusion of Intervention

Through our discussions with SL of the high impact fault sequence, the team established that SL has adequately considered potential improvements and based on the limited sample examined, the ONR inspection team considered that SL has carried out an adequate Long Term Periodic Review (LTPR) of WTC. Consequently, I have awarded an IIS rating of 3 (Adequate) against LC15.

As part of its LC15 arrangements, SL will need to produce a Confirmation of Safety Letter (COSL) to confirm the facility has adequately implemented the LTPR and that it considers risks have been reduced as low as reasonably practicable (ALARP). I have, therefore, raised a Regulatory Issue to capture the three areas for resolution mentioned identified above to provide visibility that they are adequately addressed in the COSL.