Office for Nuclear Regulation

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Compliance Inspection of Licence Condition 22 (modification or experiment on existing plant) of the Magnox Swarf Storage Silo (MSSS) at Sellafield

Executive summary

Purpose of Intervention

The Office for Nuclear Regulation (ONR) undertakes all regulatory interaction with the Sellafield site licensee (Sellafield Limited, SL) against a strategy defined by the ONR Sellafield, Decommissioning, Fuel and Waste (SDFW) Division. In accordance with that Strategy, a Licence Condition compliance inspection of the Decommissioning Directorate was carried out as identified within the planned inspection schedule for Decommissioning.

This planned intervention was undertaken to determine if the MSSS facility is adequately implementing SL's site-wide and local arrangements for compliance with Licence Condition 22 (LC22) (modifications or experiments on existing plant). The Magnox Swarf Storage Silo (MSSS) facility was chosen because of the radiological hazard associated with the waste inventory and because the facility is preparing to conduct waste retrieval operations.

Interventions Carried Out by ONR

LC 22 requires that the licensee implements adequate arrangements to control any modification or experiment carried out on any part of the existing plant or processes which may affect safety. On 7 November 2017 I carried out a planned, one-day, on-site LC 22 compliance inspection within the Decommissioning Operating Unit at the MSSS facility. The inspection comprised discussions with SL staff and reviews of relevant plant records and other documentation. In carrying out this inspection, I used the ONR guidance in ONR-INSP-GD-022, Revision 3, issued in December 2014.

The inspection was supported by the SL MSSS Internal Regulator for Compliance.

Explanation of Judgement if Safety System Not Judged to be Adequate

This was not a system based inspection, and therefore no judgement has been made of the adequacy of implementation of any part of these safety cases.

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

My inspection undertook a detailed examination of plant records associated with the ongoing MSSS work and sampled a number of areas including:

SL had recently conducted a review of overdue modifications which indicated 15 permanent modifications with Plant Modification Proposals (PMPs) open for more than 3 years that remained to be closed. The Operations Manager stated actions had been placed to address this backlog but the benefits had yet to be realised. The issue of overdue PMPs is a site-wide problem and is already the subject of ONR Regulatory Issue 2952 (level 3). I have requested that SL Internal Regulator monitor the effectiveness of MSSS actions to reduce the number of overdue modifications.

In general, I found evidence of a good standard of implementation by the MSSS facility of the licensee's LC22 arrangements for MSSS. In particular, I noted that senior MSSS staff were closely aware of all the recent and currently-live modifications that were sampled as part of this inspection.

Although there was a generally good standard of implementation, I noted a small number of minor quality shortfalls none of which affected safety. However, I noted the potential for such errors to have safety significance and those MSSS governance arrangements had missed them. The MSSS senior staff accepted this shortfall and the SL internal regulator will follow this up to ensure that quality errors are reduced.

I judged that one sampled PMP, lacked clarity with respect to its safety categorisation and commissioning arrangements and, further, did not fully articulate its dependence on an associated modification. This PMP is currently subject to ONR permissioning. I have therefore raised 3 regulatory issues to seek improvement to the clarity of the PMP which I, as the ONR MSSS Project Inspector, will pursue close out as part of ONR's the permissioning decision.

Conclusion of Intervention

Based on the areas sampled and evidence gathered, I consider that the licensee is compliant with its duties under LC 22 although some minor shortfalls were identified. It is my opinion that an inspection rating of GREEN (no formal action required) is appropriate.