Office for Nuclear Regulation

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System Based Inspection of WVP Line 3 Sheild Doors - follow up enquiries on INF1 2018/441

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 Sub Division. In accordance with that strategy, a System Based Inspection (SBI) was carried out on the Operational Waste Facilities Operating Unit (OU), as planned, in July 2018. 

Interventions Carried Out by ONR

On 11-12 July 2018, I, the site inspector for the operational waste facilities, accompanied by an ONR radiological protection specialist, carried out a shielding SBI on the line 3 vitrification cell within the High Level Waste Plants (HLWP). 

The purpose of this inspection was for ONR to examine whether the licensee’s safety case claims in respect of the HLWP line 3 shield doors have been adequately implemented. The areas targeted were those providing key safety support to the primary shielding function of the breakdown wash cell and pour cell shield doors.

ONR’s SBI process examines evidence to determine compliance against six Licence Conditions (LC). These LC’s, listed below, have been selected in view of their relevance to ensuring nuclear safety and provide a structured approach to determining whether the safety case has been implemented adequately through the system being inspected.

LC 10 requires SL to make and implement adequate arrangements for suitable training for all those on site who have responsibility for any operations which may affect safety.

LC23 requires SL to produce an adequate safety case to demonstrate the safety of its operations, and to identify the conditions and limits necessary in the interests of safety.

LC24 requires SL to ensure that all operations which may affect safety are carried out in accordance with written instructions.

LC27 requires SL to ensure that a plant is not operated, inspected, maintained or tested unless suitable safety mechanisms, devices and circuits are properly connected and in good working order.

LC28 requires SL to make and implement adequate arrangements for the regular and systematic examination, inspection, maintenance and testing of all plant which may affect safety.

LC34 requires SL to ensure, so far as is reasonably practicable, that radioactive material and radioactive waste on the site is at all times adequately controlled or contained so that it cannot leak or otherwise escape from such control or containment.

On this occasion, LC 34 (leakage and escape of radioactive materials) was not included in the System Based Inspection as ONR judged that it was not directly applicable to the system under consideration.

I also conducted follow up enquires on a recent event which occurred in HLWP and was reported under INF1 2018/441.   

Explanation of Judgement if Safety System Not Judged to be Adequate

Based upon the areas sampled I judged that the safety case requirements for the line 3 shield doors have been adequately implemented.

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

For LC10 I sampled the training of two operators associated with shield door moves and one of the maintenance team who carried out the last maintenance of one of the Line 3 shield doors.  From the evidence provided I was satisfied that individuals sampled had completed the mandatory requirements and were deemed suitably qualified and experienced to conduct and/or supervise line 3 shield door operations.  I therefore judge that the required standard was met and an inspection rating of Green (no formal action) is appropriate against LC10.

For LC23 I reviewed the current safety case for the line 3 shield doors and was satisfied that appropriate limits and conditions are identified to protect against the faults identified within the safety case. Based on the evidence sampled, I judge that the required standard is met and an inspection rating of Green (no formal action) is appropriate against LC23.

For LC24 I was satisfied that the associated operating Instructions were adequate to ensure compliance with the limits and conditions identified in the safety case. I therefore judge that the required standard was met and an inspection rating of Green (no formal action) is appropriate against LC24

For LC27 I was satisfied that the appropriate safety measures had been identified within the safety case and had been correctly designated.  Due to a plant issue I was unable to conduct a plant walkdown to confirm they are connected and in working order.  However, given their function and fail safe mode of operation I judged that any malfunction would be apparent to the operators.

For LC28 I sampled the maintenance of the hydraulic cubicles supporting operation of the line 3 breakdown wash cell shield doors and the pour wash cell shield doors. I reviewed the completed maintenance records for the last two maintenance tasks.  Whilst no significant shortfalls were identified, I gave some advice on areas for potential improvement in both the written instructions and the completed records.  This was taken on board by SL who undertook to include them during the current review.  Based on the areas sampled, I judged that the shield doors were being adequately maintained. I therefore judge that the required standard was met and an inspection rating of Green (no formal action) is appropriate against LC28.

As a result of my follow up enquiries on the event reported under INF1 2018/441 I am satisfied that SL are taking the appropriate actions to address any learning and that the event does not meet the ONR formal investigation criteria.

The intervention was performed in line with ONR's guidance requirements (as described in our technical inspection guides) in the areas inspected.

Conclusion of Intervention

From the evidence gathered during this intervention, I do not consider there to be any matters that have the potential to impact significantly on nuclear safety.    

At present, no additional regulatory action is needed over and above the planned interventions within the Operational Waste Facilities Operating Unit at the Sellafield Nuclear Site as set out in the Integrated Intervention Strategy, which will continue as planned.