Office for Nuclear Regulation

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Sellafield - System Based Inspection on the high active and medium active cycles

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) of the High Active (HA) and Medium Active (MA) cycle systems within the Magnox Reprocessing facility (MRF) , which is part of the Magnox Operating Unit (OU) was planned.  The purpose of this planned inspection was for ONR to confirm the adequacy of implementation of the licensee’s safety case claims in respect of this system.

As part of each SBI, ONR examines evidence of the adequate implementation of six pre-defined licence conditions.  These licence conditions (listed below) have been selected because of their importance to nuclear safety, and are defined within the ONR’s formal process for delivery of an SBI.

Interventions Carried Out by ONR

LC 10 requires SL to make and implement adequate arrangements for suitable training of those who have responsibility for any operations that may affect safety.

LC 23 requires SL to produce adequate safety cases to demonstrate the safety of its operations, and to identify the operating conditions and limits necessary in the interests of safety.

LC 24 requires SL to make and implement adequate arrangements for the provision of suitable written instructions for undertaking any operation that may affect safety.

LC 27 requires SL to ensure that, before a system is operated, inspected, maintained or tested, there are suitable and sufficient safety mechanisms, devices and circuits properly connected and in good working order.

LC 28 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.

LC 34 requires SL to ensure that its radioactive material and radioactive waste is at all times adequately controlled and contained, and that no leak or escape of that material or waste can take place without being detected.

I led a two-day, on-site, SBI of the HA/MA cycle system within the MRF.  The inspection comprised discussions with SL staff, plant walk downs and reviews of plant records and other documentation.

Explanation of Judgement if Safety System Not Judged to be Adequate

The HA/MA cycle system was judged to be adequate.

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

From the evidence examined during this inspection, I consider that SL has adequately implemented those claims within the facility safety case that I sampled.

As part of the scope of this SBI, I considered if the related facility safety case might require an ONR assessment of adequacy in a timeframe shorter than currently planned.  Although the safety assessment documentation was originally written around 2005, it was subsequently modified by a number of operational safety memoranda around 2015, following the periodic review of safety.  Though fewer changes to the safety measures were made compared with the previous system inspected within MRF, we found that the detailed case is structured in a manner that does not always allow efficient extraction of information, however, the information provided to operators through the instructions was accurately transposed.  The facility is expected to complete operations by the end of 2020, based on the evidence sampled I have no reason to recommend an early assessment of the safety case for this system.

I reviewed evidence of adequate training and implementation of the safety case against the system function and found good knowledge demonstrated from operators and supervisors.

I sampled a range of maintenance activities for components across the system and consider that, in all cases, SL provided adequate evidence of asset maintenance and inspection. However, I did find two areas with minor shortfalls against relevant good practice, which I have raised two level 4 regulatory issues against, as areas for improvement.

One regulatory issue relates to the system health reports rating a number of areas as poor (red), even though justifications for not meeting modern standards have been made and accepted.  I judged that this could result in areas that are genuinely rated “poor”, which require improvements, being less visible amongst the other “poor” condition ratings, which will not be improved on this facility. This may also lead to the erroneous impression that it is acceptable for system health to be rated as “poor”.

The second regulatory issue relates to the quality of the maintenance instructions, which result in maintainers making judgements or undertake calculations on plant to determine whether calibration tolerances are met when in many cases it is possible to provide values to compare against.  There is also a potential to improve fault identification by maintainers from easier access to prior maintenance records, during maintenance activities.

I observed a number of minor areas for improvement that I judged to not require ONR follow-up. These will be followed up by SL’s internal regulator and I will follow up through routine engagements, as necessary.

Based on the sampled evidence, I consider that a rating of Green (no formal action) is merited for Licence Conditions 10, 23, 24, 27, 28 and 34.

Conclusion of Intervention

From the evidence sampled during this inspection, I judge that the licensee has implemented adequately the sampled claims within its safety case.  Additionally, on the basis of the evidence requested and reviewed, I consider that the licensee’s formal arrangements for compliance with Licence Conditions 10, 23, 24, 27, 28 and 34 are also being implemented adequately. Two ONR Regulatory Issues were raised to be followed up by ONR. I judged that other minor areas for improvement observed can be followed up by SL’s internal regulator, as necessary.