Under Licence Condition 30(3) the licensee, EDF Energy Nuclear Generation Limited (NGL) requires consent from the Office for Nuclear Regulation (ONR) to start up Heysham 2 Reactor 8 after a periodic shutdown. Whilst Reactor 8 was shut down, and routine maintenance activities were being undertaken on the steam relief valves, it was reported to the ONR nominated site inspector that there had been a failure of a structural steelwork stool at the end of a beam that supports the main steam pipework.
My intervention was reactive and unplanned and its purpose was to carry out follow-up enquiries so that ONR could more fully understand the nature and extent of the steelwork failure, the actions that NGL were taking to investigate the incident and the effects of the incident on NGL’s safety justification for returning Reactor 8 to service after completion of the periodic shutdown. My intervention has also considered the potential impact of the steelwork failure on Reactor 7 at Heysham 2 Power Station and Reactors 1 and 2 at Torness Power Station, all of which are currently operational.
An ONR civil engineering specialist inspector together with the nominated site inspector and a structural integrity specialist inspector reviewed the licensee’s response to the failure of the structural steelwork beam supporting the main steam pipework. The status, suitability and progress of the licensee’s own investigation was considered and whether this incident met the criteria to carry out a formal investigation.
In undertaking my incident follow-up enquiries my intervention has considered, by sampling, whether NGL has demonstrated compliance with the following Site Licence Conditions:
My intervention has also considered whether the incident has been adequately addressed to enable ONR to give consent for the restart of Reactor 8 under Licence Condition 30(3).
This intervention was performed in line with ONR’s guidance requirements (as described in our technical inspection guides, which can be found at ) for the area inspected.
I judged from the sampled activities and the records provided that NGL is undertaking an appropriate investigation into the steelwork failure in accordance with its arrangements.
From the information sampled I have concluded that the steel support stool that failed, together with the similar support stools in the other three quadrants of Reactor 8, have been removed and replaced with a more robust stool that has been justified by an appropriate safety assessment and calculations.
I have noted NGL’s commitment to replace the equivalent steel support stools on Reactor 7 and on the two reactors at Torness Power Station as soon as reasonably practicable, and that no valve maintenance operations similar to those being undertaken on Reactor 8 when the steelwork failed will be undertaken on these other reactors until the replacement stools have been fitted.
I was unable to obtain sufficient assurance that NGL has maintained an accessible copy of calculations that justify the adequacy of the structural steelwork supporting the main steam pipework. I have therefore placed an action on NGL to provide further substantiation prior to ONR granting consent under Licence Condition 30(3) for the re-start of Reactor 8.
I was unable to obtain sufficient information to confirm that NGL has complied with its arrangements under Licence Condition 22 in carrying out modifications to the structural steelwork in order to undertake valve maintenance activities. I have raised an action on NGL to supply further information so that ONR can assess the extent of NGL’s compliance with Licence Condition 22, and will follow this matter up with the licensee following completion of the periodic shutdown.
I was unable to obtain sufficient information to confirm that NGL has complied with its arrangements for carrying out lifting operations to remove the top sections of the steam release valves during routine maintenance activities. I will follow this matter up with the licensee following completion of the periodic shutdown.
I was unable to obtain any evidence that the structural steelwork supporting the main steam main has been subject to regular and systematic examination by a suitably qualified and experienced person. I have raised an action on NGL to supply further information, and will follow this matter up with the licensee following completion of the periodic shutdown.
Based on my findings I judge that the following inspection rating against Licence Condition 22 is appropriate: Amber. The reason for my judgement is that my inspection has revealed potentially significant or systematic failure to implement or meet licence compliance arrangements.
My intervention has gathered further information relating to a failure of structural steelwork during planned maintenance activities on Reactor 8. I have identified a number of actions on NGL that will require regulatory follow up and I have captured these in two ONR regulatory issues.
Having consulted ONR’s guidance, I consider that the incident does not meet ONR’s investigation criteria however I intend to follow up the issues raised during this intervention by writing to the licensee in order to seek assurances that appropriate lessons have been learnt.
The findings of this intervention will inform ONR’s overall decision whether to issue consent for start-up of Reactor 8 on completion of its 2016 periodic shutdown.