Office for Nuclear Regulation

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To conduct a system inspection, a LC7 compliance inspection and undertake routine regulatory interactions with Sellafield Limited

Executive summary

Purpose of intervention

This intervention was undertaken on 27 – 30 April 2015 at Sellafield Limited’s (SL’s) Sellafield nuclear licensed site in Cumbria.

Inspection of Licence Condition (LC) compliance at nuclear licensed sites forms a significant part of ONR’s activities.  ONR’s Sellafield Programme has defined a programme of system inspections and LC compliance inspections to be undertaken on the Sellafield site; this is a key aspect of ONR’s regulatory strategy for the Sellafield site.  Undertaking this intervention is consistent with this strategy, and is identified on ONR’s PP4 inspection plan which covers Sellafield Limited’s Magnox Operating Unit.

Interventions Carried Out by ONR

The intervention comprised:

The purpose of the criticality detection system (CIDAS) within the Magnox Reprocessing Separation plant is to detect criticality events and activate alarms to initiate a prompt evacuation of the plant.  The purpose of the plant’s neutron monitoring system (NMS) is to continuously monitor process liquors to ensure that build-ups of fissile material do not occur so that the concentration of fissile material within the liquor stays below predetermined safe levels.  My system inspection sought to determine whether safety case requirements are implemented and key equipment is both available and adequately maintained.  The implementation of the licensee’s arrangements for the following LCs were tested during the system inspection:

My inspection comprised reviews of SL’s safety case and other documentation, interviews with SL staff and visiting the plant, e.g. to view key equipment.  I was accompanied by ONR specialist criticality and control and instrumentation inspectors and members of SL’s internal regulator (SLIR). 

Licence Condition 7 requires the licensee to make and implement adequate arrangements for the notification, recording, investigation and reporting of incidents occurring on the site. My inspection here looked at the implementation of Sellafield Limited’s site arrangements for LC7 at Magnox Reprocessing.  I discussed the implementation of these arrangements with SL staff and reviewed documentation.

I also attended meetings:

Explanation of Judgement if Safety System Not Judged to be Adequate

Based on sampling inspection, the NMS within the Plutonium Purification Cell of the Magnox Reprocessing Separation plant was judged to be consistent with the requirements of the safety case.  The CIDAS is not claimed in the safety case.

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

For the system MAG05a ‘Criticality detection and neutron monitoring’ within the Magnox Reprocessing Separation Plant I judged the following IIS ratings to be appropriate:

Based on my sample, I judged that the NMS within the Magnox Reprocessing Separation plant is consistent with safety case requirements.  The CIDAS is not however claimed in the safety case.

During the course of this inspection I was advised that the Medium Active Evaporation and Thermal Denitration plant (another plant in this Operating Unit) has neither a CIDAS nor a CIDAS-omission case even though criticality is considered by SL to be a credible plant fault. 

I raised three regulatory issues and a number of actions which I will follow up as part of my routine regulatory interactions with the licensee.   However I have concerns about the safety case for Magnox Separation in that the CIDAS is not claimed in the safety case even though it is needed to prompt personnel evacuation in the event of a criticality event.  In view of this concern, I recommend ONR carries out further work to examine the adequacy of this aspect of the plant safety case.

In my LC7 inspection I identified an apparent lack of awareness of SL’s site process for assigning appropriate levels of investigations to events.  Applying this process inconsistently has the potential to result in the plant not adequately identifying apparent causes and corrective actions.  ONR’s guidance on LC7 confirms that the types of investigation used should be appropriate to the significance of the event.  I have placed an action and raised a regulatory issue to address this deficiency.  I nevertheless judge that the fundamental requirements of ONR’s guidance are met but there are specific weaknesses, and therefore judge an IIS rating of 4 (below standard) to be appropriate against LC7 ‘Incidents on the site’.

I attended a progress meeting to discuss the planned import of legacy fuel to FHP.  The focus of the meeting was to clearly communicate my expectations of the pre-requisites I would expect to be in place at FHP prior to the import of legacy fuel.  The licensee noted my views.

I attended one in a series of quarterly level 4 meetings with the head of the Magnox Operating Unit and the heads of the facilities within the Operating Unit.  The aim of the meeting was to discuss topical issues and inspection feedback (from ONR and SLIR).  I was reassured there is a good alignment between ONR and SLIR in terms of regulatory expectations, and that any concerns we raise are taken seriously by the licensee.

A structural integrity specialist inspector facilitated a number of interactive discussion sessions to provide guidance and advice on ONR’s expectations on the examination and inspection of metal plant:

Conclusion of Intervention

Four regulatory issues and a number of actions were raised as a result of this intervention (arising from the system inspection and the LC7 compliance inspection). I will engage with the licensee to manage their close out as part of my normal regulatory interactions with the licensee, and will determine whether any further regulatory action is required.