- Date released
- 27 November 2020
- Request number
- 202010046
- Release of information under
- Freedom of Information Act 2000 (FOIA)
Information requested
I see it has been reported that the cause of the valve failure at Olkiluoto has been determined to be stress corrosion cracking https://www.montelnews.com/fr/story/fissures-sur-les-soupapes-de-lepr-olkiluoto-3--rgulateur/1160611
At a recent online conference Humphrey Cadoux-Hudson of EDF said that the valve issue had been “found and fixed” at Taishan (and that there was plenty of time to sort it out at Hinkley).
Could you please confirm;
a) What detailed information you have received from the Finnish regulator about the cause of the valve failure
b) Whether or not you have received confirmation from your French and/or Chinese counterparts that the valves were “found and fixed” at Taishan (in both reactors) and when this happened?
c) What information you have about how long Taishan-1 and/or Taishan-2 have been on outage in the last 12 months and, if this was longer than scheduled, what the reason was?
d) What action ONR is taking as a result of the findings at Olkiluoto?
e) Your understanding of when Hinkley Point needs to have its safety valves manufactured if the project is not to be delayed (I note you said these were due to be manufactured later this year)
Information released
Please find a response to each of your questions in turn below. For your queries a, b and c, these have been treated as an FOI request and I can confirm that under Section 1 of the FOIA we do hold some of the information requested. For questions d and e in your request, we consider these as general enquiries about our work and are not requests for information therefore there have been treated as general enquiries.
a) What detailed information you have received from the Finnish regulator about the cause of the valve failure?
We received information from the Finnish regulator about the cause of the valve failure through a presentation they gave during a routine meeting in May this year. This included preliminary results from Framatome’s (EPR nuclear island vendor) root cause analysis of the value failure. This analysis suggested that the failure of the mechanical pilot valve component was the result of hydrogen induced stress corrosion cracking due to the presence of local pollution.
b) Whether or not you have received confirmation from your French and/or Chinese counterparts that the valves were “found and fixed” at Taishan (in both reactors) and when this happened?
We have not received confirmation from our counterparts on this matter. However, we expect this will be discussed as part of our ongoing routine information exchange meetings. Due to Covid-19 the next meeting has not yet been confirmed but we anticipate it will take place in the next 2-3 months. Should an ad hoc meeting be required sooner then this would be arranged.
c) What information you have about how long Taishan-1 and/or Taishan-2 have been on outage in the last 12 months and, if this was longer than scheduled, what the reason was?
In February this year we were advised of a planned outage at Taishan-1, scheduled for 3 July – 19 September. We intend to confirm this took place as planned at our next meeting with the Chinese regulator in early 2021, exact date still to be confirmed.
The first refuelling outage for Taishan-2 is scheduled for 2021.
We are not aware of any unplanned outages on either Taishan-1 or Taishan-2 in the past twelve months. This again will also be discussed with the Chinese regulator at a future information exchange engagement.
d) What action ONR is taking as a result of the findings at Olkiluoto?
We will continue to liaise with the other EPR regulators to benefit from the lessons learned from the lead EPRs. We will also engage with the Hinkley Point C (HPC) licensee to ensure that the learning is addressed appropriately with any reasonably practicable measures taken to reduce the likelihood of such failures at HPC.
We have recently received an update on the HPC licensee’s engagements with Framatome from which it is understood that the first barrier of defence for HPC will be enhanced cleaning and preservation requirements to avoid pollution.
It is also understood that an alternative design and/ or material for the affected component is being considered as a second barrier to limit the risk of stress corrosion cracking in case of residual pollution. If the affected component is modified we would expect NNB GenCo to demonstrate that adequate testing of the pilot valve has been completed prior to installation at site to verify that the performance requirements are met.
e) Your understanding of when Hinkley Point needs to have its safety valves manufactured if the project is not to be delayed (I note you said these were due to be manufactured later this year)
We do not have details of the site demand date for the HPC Pressuriser Safety Relief Valves (PSRVs) at this time. However, we are confident that HPC are learning lessons from other EPR projects and have the time to make any modifications should they be necessary. Please be assured that our focus will be on the adequacy of the PSRVs to meet the safety case requirements and ensuring any such learning has been taken into account.
Exemptions applied
N/A
PIT (Public Interest Test) if applicable
N/A