- Site: Sellafield
- IR number: 21-026
- Date: May 2021
- LC numbers: 10, 23, 24, 27, 28, 34
Executive summary
Purpose of Intervention
In accordance with the Office for Nuclear Regulation’s (ONR’s) Sellafield Strategy, each year ONR performs a series of planned system based inspections (SBIs) targeted on key safety significant systems. The purpose of this particular intervention was to undertake a systems-based inspection (SBI) of the Sellafield Highly Active Liquor Evaporation and Storage (HALES) Buffer Storage Facility and Transfer Tower containment systems with a focus on the civil structures, sumps and safety systems used to ensure the safe containment of liquid effluent during normal operation and in the event of a fault or accident. The inspection examined evidence to determine compliance against licence conditions (LC) 10, 23, 24, 27, 28 and 34.
Interventions Carried Out by ONR
ONR carried-out a planned two-day SBI of the HALES Buffer Storage Facility and Transfer Tower with a focus on the civil structures, sumps and safety systems used to ensure the safe containment of liquid effluent. The inspection team was led by the ONR Site Inspector and an ONR Civil Engineering Specialist Inspector. We were supported by a member of the Sellafield Limited (SL) internal regulator: Nuclear Intelligence & Independent Oversight (NI&IO). The NI&IO representative was considered a full member of the inspection team and was involved in all aspects of planning and conducting the inspection.
The intent of the inspection was to verify the adequacy of the implementation of the HALES safety case with respect to the containment of radioactive liquor. This included determining a compliance rating in respect of the aforementioned LCs. The inspection involved reviewing a sample of safety case claims and then confirming the adequacy of implementation with respect to a number of aspects of the Buffer Storage Facility and Transfer Tower containment systems including: their current condition and availability (LC 27 – Safety mechanisms, devices and circuits); upkeep and testing (LC 28 – Examination, inspection, maintenance and testing); maintenance of the safe operating envelope (LC 23 – Operating rules) using appropriate procedures (LC 24 – Operating instructions) and the training of personnel (LC 10 – Training). Overall, the ability of the containment systems to prevent the leakage of radioactive material is addressed through LC 34 (– Leakage and escape of radioactive material and radioactive waste) and is the key element, for this SBI, of the overall judgement that the overall system for containment has been adequacy implemented.
Explanation of Judgement if Safety System Not Judged to be Adequate
Not applicable – the safety system was judged to be adequate.
Key Findings, Inspector's Opinions and Reasons for Judgements Made
From the evidence sampled we judge that an inspection rating of GREEN (no formal action) is appropriate against LC 10.
The HALES safety case clearance certificate contains a number of safety case requirements to ensure the correct and safe transfer of liquor between tanks, several of which are implemented via operator instructions (OIs) for such transfer activities. In sampling the two most recent uses of a transfer OI we observed that the instructions had not been completed properly. Additionally, with regard to the required confirmation that the anticipated volume of liquor had reached the intended destination, it appears there is no suitable means by which operators can positively comply. Despite the knowledge demonstrated by the operators and the duly authorised person (DAP) we spoke to during our visit, and recognising the defence-in-depth provided by leak detection and sump systems we, on balance, consider that a rating of AMBER against LCs 23 and 24 is appropriate in order to seek improvement here.
We located a number of safety mechanisms, devices and circuits (SMDC) that appeared to be in working order. We did note a number of standing alarms relating to several items of equipment, but discussion with the operators gave confidence that these alarms were understood and being managed. We provided advice that standing alarms should not be tolerated for long periods and faults needed to be resolved to avoid operator distraction and the NI&IO internal regulator will be following-up on this. We also noted a number of defect tags identifying known faults. Primarily, these related to non-safety significant equipment and/or items for which there were duplicate indications. Nonetheless, some of the tags dated back a number of years and the NI&IO internal regulator will be following-up to understand this further. Overall, we consider that a rating of GREEN (no formal action) is appropriate against LC 27.
We considered the civil structure and safety system asset condition to be adequate although we recognise the challenges due to the age of the facility and the need for progress with some key remediation projects. We were satisfied with the inspection and maintenance programme in place but provided advice in relation to the ongoing monitoring of the roof waterproofing and in relation to consideration of new non-destructive testing technologies. We judge a rating of GREEN is appropriate (no formal action) against LC 28.
The safe conduction of liquor transfer operations, the ongoing integrity of civil structures and containment barriers, and the systems for detecting and responding to leaks from the intended place of containment of the liquors at HALES are key elements of the means by which the licensee must ensure their control and containment. As such, compliance with LC 34, alongside the adequacy of implementation of the containment aspects of the HALES safety case, are an outcome of the above findings describing specific aspects under other LCs. On balance, we judge that an inspection rating of GREEN (no formal action) is appropriate against LC 34.
SL self-identified poor levels of housekeeping in some areas of the facility. Whilst we acknowledged the challenges of radiation dose uptake, managing Covid risk, and in prioritising work, we consider that work is required to improve the situation to ensure full plant access in case of emergency, to limit fire loading and, in particular, to encourage individuals to respect and look after their workplace. The NI&IO internal regulator will be following-up on this.
During the plant visit we also highlighted a number of shortfalls in health physics (HP) barriers and signage on the Buffer Storage Building roof. We were assured that the HP team would be rectifying these immediately following our visit.
Conclusion of Intervention
From the evidence sampled during the inspection, the inspection team judges that the licensee has adequately implemented the overall system for containment at the HALES Buffer Storage Facility and the Transfer Tower. Given some of the identified shortfalls, this judgment is a balance of the evidence and recognises that there are multiple barriers to prevent the release of radioactive material.
We identified some inadequacies with regard to the implementation of some safety case requirements relating to the transfer of liquor between tanks. These shortfalls led to AMBER ratings against LCs 23 and 24. The ONR Enforcement Management Model (EMM) will be applied to determine an appropriate regulatory response and, further to this, a candidate level 3 regulatory issue will be raised. LCs 10, 27, 28 and 34 were rated GREEN; however, SL NI&IO will be following-up lower-level findings in some areas and ONR will also be raising a level 4 regulatory issue to track SL’s delivery of some upcoming hazard remediation projects.
LC 12 had been initially rated (as GREEN) but this has not been formalised as it is not part of the standard LC suite for an SBI.