Office for Nuclear Regulation

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System Based Inspection on Waste Encapsulation Plant (Ventilation System)

Executive summary

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 Waste Encapsulation Plant, as planned, on 8 and 9th October 2019.

The purpose of this inspection was for ONR to examine whether the licensee’s safety case claims in respect of the Waste Encapsulation Plant (WEP), which form part of SL’s Spent Fuel Management – Operational Waste Facilities, ventilation system have been adequately implemented.

In addition, on the 9th October I carried out preliminary enquiries into an incident at WEP.

Interventions Carried Out by ONR

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. 

Explanation of Judgement if Safety System Not Judged to be Adequate

Based upon the areas sampled I judge that the safety case requirements for the WEP ventilation system have been adequately implemented.

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

Whilst some minor opportunities for improvements were identified, from the areas ONR targeted and the evidence ONR examined during this inspection I consider that LCs 24, 27, 28 and 34 have been adequately implemented in relation to the safety case claims on the WEP ventilation systems. I awarded inspection ratings of Green (No formal action) for LCs 24, 27, 28 and 34.

For LC 10 (Training), I targeted the training of an Operations Team Leader Duly Authorised Person (DAP), a Maintenance Team Leader DAP, a Ventilation Systems Engineer and a Maintenance Engineer associated with operational activities of the ventilation system and maintenance of the pre-selected SM, SRE and SFs. I judged that there was a minor shortfall against relevant good practice with regard to training of a Maintenance Engineer who had not completed a training course required for a maintenance task carried out on the WEP Ventilation system and I have raised a Level 4 Regulatory Issue to track progress by the licensee to address this shortfall. It was noted that this was the only individual in the sample that had not completed the required training. This shortfall has been recognised previously by ONR and there is currently an ONR Level 3 Regulatory Issue raised to address this at the SL Corporate level. Notwithstanding the minor shortfall identified in the Maintenance Engineers training; overall I judge that the required standard is met and an inspection rating of Green (no formal action) is appropriate against LC10.

For LC 23 (Operating Rules) I targeted the relevant Operating Rules (ORs) in connection with WEP ventilation systems current safety case. During the plant walk round I visited the filter cave where the C3/5 filters are stored following their operational lifetime before being transferred to filter flasks. The licensee routinely stores more filters in the cave than the Operating Assumption permitted, I judged this to be a minor shortfall and have raised a Level 4 regulatory issue. Notwithstanding the minor shortfall identified in the filter cave; overall I was satisfied that the safety case clearly identifies the fault sequences and the WEP plant has appropriate limits and conditions to protect against the faults identified within the safety case. Based on the evidence sampled I judge that an inspection rating of Green (no formal action required) is merited for LC 23.  

During the system based inspection of the ventilation systems, I noted a minor shortfall in relation to the maintenance of the fire dampers in WEP. I raised a Level 4 Regulatory Issue to track progress by the licensee to address this shortfall.

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

I carried out Preliminary Enquiries into an incident where there was a failure of a level monitoring gauge on the centrifuge cake vessel in WEP. On the basis of our discussions I judge that this event does not meet the ONR investigation criteria as there was no challenge to nuclear safety or release of radioactive material.

Conclusion of Intervention

From the evidence sampled during the inspection, I judge that SL has adequately implemented the relevant claims in the safety case and that the formal arrangements for LCs 10, 23, 24, 27, 28 and 34 are being adequately implemented.

I have raised three Level 4 Regulatory Issues in relation to the training of Maintenance Engineers, fire dampers in WEP and the filters stored in the filter caves.

Based upon the areas sampled I judged that the safety case requirements for the WEP ventilation system have been adequately implemented.