This Office for Nuclear Regulation (ONR) inspection was carried out to support ONR’s assessment and evaluation of EDF Energy Nuclear Generation Ltd (EDF Energy) effectiveness in implementing the Sizewell B Dry Fuel Store Safety Case, NS/NP 7575, EC 338898S, Stage Submission 1 Revision 1 (SS1 Rev 1).
This inspection targeted EDF Energy’s irradiated fuel selection and sentencing arrangements for dry storage of fuel and was focussed on fuel integrity evaluation and, given the complexity of the tasks involved, Human Factors interactions. The inspection built on ONR’s assessment work undertaken on SS1, Rev 1 and addressed the following Licence Conditions (LC):
This was not a planned Safety System Inspection and so no judgement was made.
Overall, this inspection had a positive outcome providing ONR specialist Inspectors with evidence to support ONR’s assessment conclusion that fuel selection and sentencing was adequate and that identified risks of loading incorrect or damaged fuel had been adequately mitigated through appropriate administrative controls.
However, the ONR Human Factors inspector was of the opinion that EDF Energy had missed opportunities to develop / strengthen its case by not having involved ONR Human Factors specialists earlier in the development of its equipment and documentation.
Out of the five LCs inspected for compliance, four were rated as ‘adequate’ given that the evidence presented by EDF Energy was judged to adequately meet ONR’s guidance and standards. Some opportunities for improvement were identified which EDF Energy was aware of and actively pursuing. A rating of ‘good’ was given for LC21 compliance given that EDF Energy’s approach to validating fuel element decay burn-up values employed determination by two methods: bespoke software and manual evaluation from tables. This approach was considered robust and demonstrated a level of defence-in-depth to the process.
The inspection had a positive outcome with EDF Energy clearly having demonstrated a structured and methodical approach to irradiated fuel selection and sentencing for dry storage. The ONR Dry Fuel Store Project inspectors did however note and stress EDF Energy’s need to maintain vigilance on safety document production and delivery of training given the continuing time pressures on the Dry Fuel Store project. Consequently, there is a need to ensure that the individual parts of the project are completed to the required quality and standard so that inactive commissioning of the Dry Fuel Store may be carried out effectively.