Office for Nuclear Regulation

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LTPR Inspection of Pile Fuel Cladding Silo

Executive summary

Purpose of intervention

This intervention is part of ONR’s programme of inspections looking at Sellafield Periodic Safety Reviews (PSR) and specifically considered the Pile Fuel Cladding Silo (PFCS) Long Term Periodic Review (LTPR). The facility is operated by Sellafield Ltd. (SL) as the licensee. Hazard and risk reduction for this facility will rely on removal of the hazardous material contained in PFCS. Thus the emphasis of this intervention is on ensuring SL has adequately reviewed the extant safety case and is taking the necessary steps to continue to operate the plant in a manner that maintains risks as low as reasonably practicable (ALARP) until retrieval-related work can be started.

Intervention Carried Out by ONR

This inspection looked at 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 a fault studies scoping report and discussions with the inspection team. The intervention focused on SL’s review of the safety case in respect of a high impact fault sequence with large public dose consequences.

In addition to conducting an inspection of the facility, we attended a series of presentations on the LTPR and its implementation, and held detailed discussions on bulk waste fire fault sequences.

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

This was a successful intervention with good cooperation between all parties. The inspection revealed that SL had undertaken a pragmatic LTPR which has resulted in the licensee identifying 34 Lesser Safety Significant Improvements and an improvement plan for these.  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 needs to resolve in its Confirmation of Safety Letter (COSL) to ONR later this year:

Conclusion of Intervention

Based on the limited sample undertaken, the team considered that SL had undertaken an adequate LTPR of PFCS. As such I have awarded an IIS rating of 3 (Adequate) against LC15.

Through our discussions of the high impact fault sequence, the team established that SL had adequately considered potential improvements.  We also noted that in respect of the prevention of a combustible atmosphere accumulating in the silo, SL has made considerable improvements since the last LTPR to the inerting system and general plant condition.

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 to be ALARP. I have therefore raised a Regulatory Issue to capture the 3 areas for resolution mentioned above, so that SL’s COSL will articulate: