Office for Nuclear Regulation

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Compliance inspection of the Magnox Swarf Storage Silo (MSSS), 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) Programme. In accordance with that strategy, a Licence Condition (LC) compliance inspection of the Magnox Swarf Storage Silo (MSSS) was carried out, as planned.

The purpose of this planned inspection was for the ONR to determine the adequacy of implementation of the licensee's formal arrangements for compliance with LC 21 (Commissioning). For the inspection, ONR examined the evidence of implementation of site arrangements within MSSS, with a focus on how these have been applied in the preparations for inactive commissioning of the Silo Emptying Plant 2 (SEP2), which have been previously inspected by ONR.

The radioactive waste stored in MSSS represents a significant hazard on the site; hence, it is a priority to empty the silos as soon as is reasonably practicable. In addition to the need to ensure that structures, systems and components are commissioned to deliver any safety functional requirements, it is essential that SEP2 is commissioned efficiently and effectively by the licensee such that sustained retrieval of the waste can commence in a timely manner. Therefore, this inspection has been timed to be just prior to commencing inactive commissioning of SEP2, to provide regulatory confidence in SL's commissioning, whilst allowing opportunity for SL to correct any shortfalls or apply any identified opportunities for improvement prior to commissioning.

Interventions Carried Out by ONR

This inspection examined the compliance of the licensee with the requirements of Licence Condition (LC) 21. LC 21 requires the licensee to make and implement adequate arrangements for the commissioning of any plant or process which may affect safety.

ONR carried out a one-day, office-based, compliance inspection, focused on SL's preparation to start inactive commissioning on SEP2.

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 the safety case.

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

During the inspection, ONR sampled the SL's local MSSS arrangements and the site licence arrangements for LC21. Key areas were identified and sampled in detail:

ONR inspected SL's Commissioning Test Definition Document (CTDD) and observed a number of minor shortfalls against relevant good practice and brought these to the attention of SL who agreed to remedy the shortfalls. ONR considered these to be areas for improvement and we will monitor it as part of routine engagement without any formal action.

ONR tested SL's implementation of the commissioning processes on SEP2, examining various documents and evidence that key personnel were suitably experienced and qualified. No additional findings were raised for attention by SL.

From those areas sampled, ONR did not identify any significant shortfalls in the implementation of licensee's formal arrangements, for compliance with LC21, which would prompt an inspection of those arrangements earlier than currently planned.

Although commissioning of SEP2 has not commenced, ONR noted a number of areas for improvement against the implementation of arrangements SL has made under LC21(1). ONR noted a positive and proactive response by the licensee to these.

Conclusion of Intervention

ONR considers that, on the basis of evidence sampled at the time of this inspection, there are no shortfalls in the licensee's implementation of their LC21 arrangements, although ONR noted some areas for improvement. I therefore consider that an inspection rating of Green (No formal action) is merited in accordance with ONR's procedures.

ONR's findings and conclusions were discussed with and accepted by the licensee.