Office for Nuclear Regulation

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Plutonium Management Facility South (PMF-S) - Sellafield MOX Plant (SMP)

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 Programme.

In accordance with that Strategy, a planned compliance inspection of the Plutonium Management Facility South (PMF(S)) Sellafield MOX Plant (SMP) against Licence Conditions 32 (LC32, Accumulation of radioactive waste) and 35 (LC35, Decommissioning) was undertaken in March 2015.  The purpose of this inspection was for the ONR to confirm the adequacy of implementation of the licensee’s arrangements for compliance with these Licence Conditions.  With respect to Licence Condition 35, a key objective was to inspect progress in planning and implementing Post Operational Clean-Out (POCO), an important first step in preparing for plant decommissioning.

Interventions Carried Out by ONR

LC32 requires the licensee to make and implement adequate arrangements for minimising, so far as is reasonably practicable, the rate of production and total quantity of radioactive waste accumulated on the site at any time and for recording the waste so accumulated.

LC35 requires the licensee to make and implement adequate arrangements for the decommissioning of any plant or process that may affect safety, and to make arrangements for the production and implementation of decommissioning programmes.

My inspection was carried out over three days, comprising two half-days and one full day. This encompassed discussions with key staff, review of relevant documentation and a plant walk down. The ONR inspection team comprised the nominated site inspector, the inspector who oversees ONR’s permissioning work at Sellafield, a specialist inspector in radioactive waste and decommissioning (Nuclear Liabilities Regulation, NLR) and a non-warranted NLR specialist. The inspection was attended by a member of SL’s independent internal regulation team.

Explanation of Judgement if Safety System Not Judged to be Adequate

As this was not a Systems Based Inspection (SBI), no such judgement was made.

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

The waste management arrangements implemented in SMP provide for adequate compliance with LC32.  The licensee provided evidence of effective implementation of the waste management hierarchy through characterisation and segregation of wastes at source. This has reduced the quantity of waste routed through, for example, low level waste routes.  I observed effective interactions between the various waste management roles (e.g. Waste Advisor, Plant Solid Waste Coordinator), which is engendering positive attitudes to waste management.  The plant does not accumulate significant volumes of radioactive wastes and is making positive efforts to transfer the very small volume of Plutonium Contaminated Material (PCM) currently accumulated to the appropriate site waste route.

With respect to compliance with LC35, the plant has an initial decommissioning plan which divides the work up into stages and is implementing an overall POCO strategy, which is under revision at present.  The sequence of POCO activities has been scheduled to begin in low risk areas. This approach enables incorporation of learning from experience and the development of skills, knowledge and processes prior to tackling higher risk areas.  The plant operations team is removing and processing radioactive material arising from POCO activities (e.g. from filters) as product residues through the parts of the plant that remain operational.  This reduces the future generation of legacy wastes and the hazards to workers during decommissioning.  The work has begun only recently, but I am broadly content with the approach being taken and the progress made to date.  

I inspected samples of “Information Files” being produced for planned POCO activities and found these to be adequate. These files are intended to provide adequate records of decisions on the scope of POCO undertaken in defined areas of the plant.  This approach will enable the plant to implement a process of iterative decision cycles, to ensure safety is adequately justified whilst enabling consideration of strategic implications relating to the timing of plant decommissioning. The POCO Information file, when complete, will provide an adequate record of activities undertaken during POCO, in conjunction with systems such as drawings and plant configuration control.  The information will need to be retained in a form suitable for retrieval and future use in decommissioning.

I advised the licensee to maintain adequate focus on the configuration of the plant (including any remaining contamination and nuclear matter) on the completion of POCO, so that suitable and sufficient knowledge required for decommissioning and waste management is produced and retained, a point which the licensee accepted.  I also advised the licensee to ensure that there are adequate interactions between those undertaking POCO in the plant and the Decommissioning Operating Unit responsible for future decommissioning. 

We also advised the licensee that its well-established LC22 arrangements appear appropriate for controlling work and managing safety case updates during POCO activities, and that POCO should be considered as an extension of ‘operations’, given that the operational safety case will remain in force at the beginning of the POCO period.    

We advised the licensee to consider production of a Stream Activity Plan, to include all operations in the plant during POCO, ongoing operations, care and maintenance activities and final decommissioning. This will provide appropriate oversight of activities in the varied planned work streams and enable appropriate, proportionate regulatory engagements to be planned. The licensee accepted this advice.

Conclusion of Intervention

From the evidence sampled during this inspection, I judge that the licensee is implementing its arrangements for compliance with LC32 and LC35 adequately at SMP.  I observed evidence of good practice with respect to the management of radioactive waste arisings in the plant, and arrangements for transition of the plant from fuel manufacture operations into POCO and decommissioning. 

Further work by the licensee is however needed to assess the future waste arisings from POCO and subsequent decommissioning and to ensure that the knowledge gained during POCO (etc) can be retained and managed in a form that will enable safe decommissioning at the appropriate time.  

No regulatory issues were raised during this inspection.