Office for Nuclear Regulation

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System Based Inspection of the steam system in First Generation Magnox Storage Pond on Sellafield Ltd.’s nuclear licensed site at Sellafield, Cumbria

Executive summary

Purpose of intervention

The Office for Nuclear Regulation (ONR) undertakes all regulatory interaction with Sellafield, the Licensee (Sellafield Limited, SL) against a strategy defined by the ONR Sellafield Programme. The inspection plan PP3 for Decommissioning sets out a programme of regulatory inspections which includes a system-based inspection (SBI) of the First Generation Magnox Storage Pond Effluent Discharge Tank (FGMSP B***) steam system in September 2015.  

The purpose of this inspection was for the ONR to confirm the adequacy of implementation of SL’s safety case claims in respect of this system.

The FGMSP B*** is required to receive radioactive liquid effluent from FGMSP, Thorp Storage Pond and MSSS. It is important to these facilities that the FGMSP B*** is reliable and available to support the high hazard reduction programme for Legacy Ponds and Silos.  I selected the steam system in the FGMSP B*** and the operation of the steam ejectors. These are important to maintaining containment by mitigating the risk of a leak to ground.

Interventions Carried Out by ONR

I carried out a planned, two day on-site system based inspection of the FGMSP B*** steam system with technical support from an Office for Nuclear Regulation (ONR) mechanical specialist inspector. The inspection comprised discussions with SL staff, a plant walk down and reviews of plant records and other documentation.

As part of our system based inspection, we examined evidence of the adequate implementation of six licence conditions.  These licence conditions (listed below) have been selected in view of their importance to nuclear safety and are defined within ONR’s formal process for system based inspection.

LC10 requires SL to make and implement adequate arrangements for suitable training of those who have responsibility for any operations that may affect safety. I used NS-TAST-GD-027 rev 4 as the reference against which to assess SL’s compliance.

LC23 requires SL to produce adequate safety cases to demonstrate the safety of its operations, and to identify operating conditions and limits necessary in the interests of safety. I used NS-INSP-GD-023 rev 3 as the reference against which to assess SL’s compliance.

LC24 requires SL to make and implement adequate arrangements for the provision of suitable written instructions for undertaking any operation that may affect safety. I used NS- INSP-GD-024 rev 2 as the reference against which to assess SL’s compliance.

LC27 requires SL to ensure that, before a system is operated, inspected, maintained or tested, all safety mechanisms, devices and circuits are properly connected and in good working order. I used NS- INSP -GD-027 rev 2 as the reference against which to assess SL’s compliance.

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. I used NS- INSP-GD-028 rev 3 as the reference against which to assess SL’s compliance.

LC34 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 used NS- INSP-GD-034 rev 2 as the reference against which to assess SL’s compliance.  

Explanation of Judgement if Safety System Not Judged to be Adequate

I judged this safety system to be an adequate implementation of the safety case.

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

From the evidence examined during this inspection, I consider that SL has implemented adequately those claims within the facility safety case that relate to the risk of a loss of containment of radioactive liquid effluents from the primary containment, potentially resulting in a leak to ground.   

In performing this system-based inspection, I have considered if the supporting safety case for the system requires a priority assessment of its adequacy.  Based on the information gathered during this inspection, I have no reason to recommend an early assessment of this safety case.

From the limited documentation review that I conducted, I am content that, overall, the implementation of the safety case is adequate.  I have, however, found two instances where, although the fundamental requirements have been met there are specific procedural weaknesses. These are the arrangements for the substantiation of some Safety Related Equipment (SRE) and the quality of some of the Operating Instructions for the FGMSP B*** steam system. SL proactively placed actions to address these findings at the time of the inspection.

Based on discussions with facility staff and an examination of relevant training records during this inspection, I consider that SL has adequate training in place to deliver an effective response to system alarms, from both a public and plant operator safety perspective.  There was evidence of a good awareness of plant parameters, the means of ascertaining them, and a good level of wider understanding of which plant indications could be drawn upon with confidence in an emergency including in the case of sustained loss of the steam system.

The safety mechanisms appeared to be adequately maintained. I did find evidence of corrosion to the key steam system components even though the system had been refurbished recently.  SL has already recognised the importance of maintaining the availability of the steam system and is implementing a programme of work to ensure it remains fit for purpose. The measures taken by SL give me confidence that the FGMSP B*** steam system will be maintained in that state for the period that the Legacy Ponds and Silos programme requires it.  

From the samples inspected I consider that the steam system would adequately ensure that no leak or escape of radioactive material could occur without being detected by ensuring that the sampling of the primary containment sumps for radioactivity can be maintained in the event of a sustained loss of the steam system.   

Conclusion of Intervention

From the samples inspected, I judge that, overall, SL has implemented adequately the relevant claims within its safety case and that there was sufficient evidence that the formal arrangements for the licence conditions 10, 27, 28, and against are also being implemented adequately and an IIS rating of 3 (adequate) is appropriate. With regard to LC 34, from the evidence examined I am satisfied that all relevant aspects have already been covered through other parts of this inspection and so no IIS rating has been awarded to avoid double-counting. 

My inspection identified two findings where the implementation of the formal arrangements was found to be below standard. Consequently, I believe that IIS ratings of 4 (below standard) are appropriate for compliance against LCs 23 and 24. SL proactively placed actions to address these shortfalls at the time of the inspection. I have raised two regulatory issues to influence the timely delivery of these. My inspection also noted a number of minor observations.  These were shared with, and accepted by, SL during my inspection feedback.  None of these adversely affect safety.