Office for Nuclear Regulation

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ONR Readiness Inspection for Sellafield Ltd Commence Receipt and Storage of the Dounreay Exotics Phase 2 Sub-assemblies

Executive summary

Purpose of Intervention

On 11 May 2017 the Office for Nuclear Regulation (ONR) undertook an intervention on the Sellafield site to inspect Sellafield Ltd’s (SL) readiness to commence receipt and storage of the Dounreay Exotics Phase 2 sub-assemblies.

The United Kingdom (UK) Government and Nuclear Decommissioning Authority policy is to consolidate the UK’s Special Nuclear Materials (SNM) in one location. As part of this initiative, SNM from Dounreay will be transferred to Sellafield. SL’s chosen storage location for a subset of this SNM, termed the sub-assemblies, is the Sellafield Mixed Oxide (MOX) Plant (SMP). The sub-assemblies are being transferred in two phases; Phase 1, the transfer of which has already been completed and comprised the intact sub-assemblies; and Phase 2 comprising partial assemblies, loose fuel pins and clusters which will be contained within an Un-irradiated Fuel Container (UFC).

The purpose of the intervention was to inspect SL’s implementation of its Licence Condition (LC) 22 arrangements and gain assurance that for the proposed modification, SL is in a state of readiness to safely commence its implementation. The findings of the intervention will be used to inform the regulatory decision on the hold point for SL to commence the modification.    

Interventions Carried Out by ONR

The scope of this intervention was to inspect the SMP from a plant, processes and people perspective to assess its readiness to safely commence the proposed modification. The readiness inspection was undertaken against LC 22 ‘Modification or experiment on existing plant’, which requires the licensee to make and implement adequate arrangements to control any modification or experiment carried out on any part of the existing plant or processes which may affect safety. 

The inspection comprised a facility inspection and was undertaken against LC 22 in accordance with ONR guidance Technical Inspection Guide (TIG) NS-INSP-GD-022, LC22: Modification or experiment on existing plant, Revision 3, December 2014.

Explanation of Judgement if Safety System Not Judged to be Adequate

N/A – This was not a safety system inspection.

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

Based on the evidence sampled during this intervention, we have judged SL’s implementation of its LC 22 arrangements for this project as Green. With respect to ONR’s TIG NS-INSP-GD-022, SL demonstrated to our satisfaction:

That there are appropriate links to the safety case requirements for installation of the modification and that those responsible for undertaking and implementing those requirement are aware of them – this was evidenced by clear identification of safety case requirements within the operating instructions and the operators were able to clearly articulate them;

How operational learning has been reviewed and used to inform the modification’s implementation – this was evidenced by the equipment reviews and training undertaken as a direct result of the Phase 1 moves;

That training requirements have been assessed as part of the implementation of the modification – this was evidence by SL’s structured approach to training, resulting in three on the job training packs aligned to the three supporting operational instructions.

That procedures and instructions have been assessed as part of the implementation of the modification and that plant simulations have usefully informed this – this was evidenced by plant trials and commissioning, which has been supported by operational, human factors and internal regulator reviews.

In relation to SL’s overall state of readiness for the proposed modification, it needs to complete its specified programme of work, which SL acknowledged. As a result, we were unable to gather sufficient evidence on certain aspects that are judged relevant to the permissioning decision at the time of the intervention including confirmation of the inert gas to be filled in the UFC and the purpose there of; evidence of SL’s quality assurance of the capability of the company performing the weld analysis to demonstrate compliance with SL’s conditions for acceptance and evidence of its structured approach to training.

SL confirmed that its condition monitoring and inspection strategy for the UFCs once in storage was still under consideration. We advised SL that although not a pre-requisite to permissioning it is our expectations that SL will develop and implement adequate arrangements and this will be pursued via a Level 4 regulatory issue going forward.  

Conclusion of Intervention

Based on our findings from the available evidence, we judge that SL’s implementation of its LC22 arrangements related to the plant modification process is adequate in this instance. From the evidence sampled, no shortfalls were identified that would prevent permission being granted for SL to commence the modification. We identified a number of actions that SL still has to provide evidence against to inform ONR’s permissioning decision. These relate to the provision of documentation and evidence supporting SL’s proposal as identified in the section above.