Executive summary
Date(s) of inspection:
January 2025
Aim of inspection
To gain assurance that Retrievals East River (RER) Waste Encapsulation Plant (WEP) is compliant with Sellafield Ltd's arrangements for Licence Condition (LC) 10 (Training), 23 (Operating Rules), 24 (Operating Instructions), 27 (Safety Mechanisms), 28 (EIMT) and 34 (Nuclear Waste) focussing on the ventilation system.
In accordance with the Office for Nuclear Regulation's (ONR's) Sellafield Strategy, each year ONR performs a series of planned inspections to seek assurance of compliance with selected licence conditions, targeted at those facilities with significant importance to nuclear safety.
Subject(s) of inspection
- LC10 - Training - Rating: GREEN
- LC23 - Operating rules - Rating: GREEN
- LC24 - Operating instructions - Rating: GREEN
- LC27 - Safety mechanisms, devices and circuits - Rating: GREEN
- LC28 - Examination, inspection, maintenance and testing - Rating: GREEN
- LC34 - Leakage and escape of radioactive material and radioactive waste - Rating: GREEN
- Overall Inspection Rating - Rating: GREEN
Key findings, inspector's opinions and reasons for judgement made
The Waste Encapsulation Plant (WEP) at Sellafield is managed by the Retrievals East River (RER) Operating Unit. The plant contains several working areas including caves and cells associated with various contamination levels C1-C5. A key safety system that controls the spread of contamination in the facility is the ventilation system. The aim of this system-based inspection was to determine the adequacy of the implementation of the WEP ventilation safety case.
I found that of the sampled staff members, evidence was presented that showed that they were all adequately trained for operations or supervision for the WEP ventilation system.
I found that although there are no formal operating rules associated with the ventilation system at WEP, one of the operating assumptions acts like an operating rule, and this is the number of used ventilation filters allowed to be stored in the C3/C5 extraction cave. I found that until 2022 the C3/C5 cave was only allowed a maximum of five filters in the cave, but this was updated to 66 in 2022. I reviewed the ODM in which this change was made and found the logic to be sensible. The number of filters in the cave was reported to be less than 66.
I found a shortfall in the emergency operating instructions for the WEP ventilation system. Although the operators and supervisors understood what to do in emergency situations associated with the WEP ventilation system, the actual instructions were not present in the sample that I reviewed. In addition, the reasoning behind having a 72 hour window after a ventilation outage before operators were required to act was not understood by the staff members that I interviewed. I will be raising a Level 4 Regulatory Issue (RI) to follow up on this shortfall. I will expect that the facility review all WEP ventilation emergency operation instructions to ensure that the required operations are written down clearly; and, that the facility discusses the 72 hour rule with all staff.
Safety mechanisms, devices and circuits had been identified in the safety case and were being maintained in accordance with the relevant written schemes.
I found that the system health report (SHR) for the WEP ventilation system to have shortfalls. We were provided with an SHR from 2019, not a recent report. This was not useful for the inspection and we instead were required to sample the background SAMdB files and VTSG reports that are the source information for writing SHRs. Sellafield staff are currently producing an up to date SHR and expect it to be complete by next month.
While on plant, I found that housekeeping was adequate, although there were a few areas that I have provided regulatory advice on to the Licensee.
Overall, I was satisfied that the WEP ventilation system safety case has been adequately implemented and the SBI outcome merited a Green rating.
Conclusion
I am of the opinion that RER has adequately implemented the safety case within the ventilation system at WEP. I did identify a few shortfalls, and consulted ONR's enforcement management model. I am satisfied these shortfalls are not serious and can be addressed with the lowest level of regulatory engagement. I have therefore awarded a Green rating (no formal action) for each of the LCs. I have raised one Level 4 Regulatory Issue (lowest level) in relation to the need to update the WEP ventilation emergency OIs and provided regulatory advice for some other minor matters recorded in the record.