Office for Nuclear Regulation

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MSSS Crane System Inspection

Executive summary

Purpose of intervention

The purpose of this intervention was to undertake a licence condition compliance inspection at the Magnox Swarf Storage Silo (MSSS) facility at Sellafield Limited, Cumbria, in line with the ONR planned inspection programme.

The ONR inspection was conducted by the nominated ONR site inspector, supported by mechanical engineering, fault studies and human factors specialist inspectors.

Interventions Carried Out by ONR

I carried out a safety case based system inspection against the Magnox Swarf Storage Silo West End Crane (WEC). Through examination of this system I performed compliance inspections against Licence Conditions 10 (training), 23 (operating rules), 24 (operating instructions), 27 (safety mechanisms, devices and circuits), 28 (examination, inspection, maintenance and testing) and 34 (leakage and escape of radioactive material and radioactive waste).

This was achieved by a focussed sampling of the licensees documentation, discussions with plant personnel and a plant walk down. These were used to determine the adequacy of the licensees arrangements in place against each licence condition for the WEC.

Explanation of Judgement if Safety System Not Judged to be Adequate

N/A - the West End Crane system was judged adequate based on this inspection.

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

I judge that overall, the WEC meets the requirements of its safety case and is adequate.

Whilst persons were found to be knowledgeable regarding the hazards and controls associated with crane operations, there were shortfalls in providing an explicit demonstration through a formal and systematic approach to competency assurance. Sellafield Limited confirmed that crane operations would be subject to the roll out of the Systematic Approach to Training within the next year in preparation for retrievals work.

The procedural controls demonstrated that the limits and conditions from the safety case were adequately implemented down through to the plant, but the structure of procedural documentation was considered complex, and would benefit from simplification to improve ease of use. Good use of visual indicators around the facility has been made to identify movement zones for the crane, relating to hazards and lift heights.

The West End Crane relies on limit switches for its positional zoning within the facility, which on visual inspection appeared to be in good order with clear safety device labelling being present. I consider that the arrangements for safety mechanisms, devices and systems were adequately implemented on the WEC.

Sellafield Limited has made good progress regarding closing out maintenance issues identified in the WEC system health report. An issue exists with the auxiliary crane, which prevents the licensee from maintaining the auxiliary hoist brake. Sellafield Limited is aware of this issue, and is considering options, and the justified life of the auxiliary crane will be limited unless a solution can be established.

Maintenance and proof test documentation inspected were judged to be complete and in good order. However the Plant Maintenance Schedule requires updating to add maintenance activities, which are currently managed through the computerised maintenance system.

A potential fault sequence was identified with the crane hook slew reeling drum, which could mean the main hoist can only be lowered when this fault occurs. Sellafield Limited is aware that this particular initiating fault may give rise to a fault sequence outside the main safety case, and plans to review the safety case and associated controls to ensure this is adequately covered. Sellafield Limited has catered for this fault condition and provided a robust argument in terms of having adequate operator instructions and overload protection devices in place, enabling it to work in a way which did not cause the fault to be initiated whilst a design solution is facilitated.

During the plant visit, when assessing the WEC, I observed a number of issues regarding conventional safety, namely working at height with particular reference to operator access devices (gates, ladders) and I queried if there was a potential for exposure to live busbars. Sellafield Limited gave an explanation regarding the adequacy of the shrouding to any electric shock hazard regarding busbars and agreed to risk-assess WEC operator access.

Conclusion of Intervention

I consider the Magnox Swarf Storage Silo West End Crane system is suitable to deliver its safety case requirements, and to operate safely at 10.5 tonne for the operations planned against it. There are some challenges to the crane system which Sellafield Limited has undertaken to address.

There are no significant regulatory issues raised by this inspection that could undermine nuclear safety; but there are a number of recommendations for minor improvements relating to maintenance and completeness of supporting documentation. Sellafield Limited has provided adequate assurance that these items will be addressed through a planned programme of work.