Office for Nuclear Regulation

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Planned system based inspection (SBI) of the Wet Inlet Facility (WIF) on Sellafield Ltd.’s nuclear licensed site at Sellafield, Cumbria

Executive summary

Purpose of intervention

In accordance with our Sellafield Strategy, a Systems Based Inspection (SBI) of the Wet Inlet Facility (WIF), a fuel storage pond was carried out as planned in June 2015.  The purpose of this inspection was for the ONR to determine the adequacy of implementation of the licensee’s safety case claims in respect of this containment system.

Interventions Carried Out by ONR

ONR carried out a 3 day inspection of the Wet Inlet Facility containment system between 9 – 11 June 2015 utilising specialists from the following technical disciplines:

In order to determine the adequacy of implementation of the licensee’s safety case claims in respect of this system, as part of all system based inspections, we examined evidence regarding the implementation of the six pre-defined licence conditions, listed below, that have been selected in view of their importance to nuclear safety and are defined within ONR’s formal process for system based inspection. This involved reviewing the applicable safety case claims and sampling, through a combination of document reviews, discussions with operators and plant inspections, suitable evidence to determine whether the LCs had been adequately implemented on the plant.

ONR assessed compliance in WIF with the following Licence Conditions (LCs) using the applicable ONR inspection guidance:

Explanation of Judgement if Safety System Not Judged to be Adequate

I judged the safety system to be adequate.

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

It is my opinion that the WIF is an adequate containment system and that Sellafield Limited has in place suitable arrangements to ensure that it is adequately maintained and its condition is monitored appropriately. Currently, I have no significant concerns with regard to its integrity. It is also my opinion that Sellafield Limited has in place suitable measures to optimise fuel clad containment by ensuring adequate management of pond water chemistry and that the Wet Inlet Facility has put in place exemplary levels of foreign material exclusion (FME) and was observed to have high standards of general housekeeping.

It is my opinion that, whilst some potential minor improvements were identified to Sellafield Ltd, LCs 10, 23, 24 and 28 are all adequately implemented in WIF. Consequently an IIS rating of 3 (Adequate) was considered appropriate.

With regard to LC27; safety mechanisms, devices and circuits, it is my opinion that an IIS rating of 2 (Good Standard) is warranted. The designated safety mechanisms were found to be in good condition and maintained appropriately with evidence of proactive management in place ensure continued availability.

It is my opinion that Sellafield Ltd has implemented robust arrangements for the prevention and detection of radioactive material. Consequently, it is my opinion that an IIS rating of 2 (Good Standard) is warranted with regard to compliance with LC34.

Conclusion of Intervention

I judge, based on the sampling completed, that the WIF safety case regarding the containment of radiological inventory is adequately implemented on the plant.

Based on the information gathered during this SBI I have no significant concerns regarding the adequacy of the technical aspects of the WIF safety case. It is my opinion, however, that the usefulness of the safety case to operators could be significantly improved. Consequently, I recommend that ONR examines this aspect at the next Long Term Periodic Review of the Wet Inlet Facility Safety Case.