- Date released: 11 September 2025
- Request number: 202507023
- Release of information under: FOI
Information requested
1. Can you please provide the latest safety case/criteria agreed by the ONR and EDF regarding the Torness nuclear power station.
1a. In particular, i am seeking information about what the new agreed safety criteria are for the cracks at the Torness nuclear power station that was agreed in May 2024. Can you confirm that this is the latest safety criteria that was agreed.
2a. What has changed from the previous safety case criteria which was that supported operation up to that which was classed as "essentially intact" - which was as one with fewer than 10% cracked bricks.
2b. Can you provide the full safety case/criteria agreed that contained the reference to what was "essentially intact" as spelt out in 2a.
2c. Can you tell me when that safety case referred to in 2a was agreed.
3. When was the last inspection of the Torness reaction cores, and at that point what were the estimated number of cracks that were found in both cores.
4. How many cracks were estimated in the Torness cores in or around April, 2024, but before May, 2024.
5. How many cracks were found (estimated or otherwise) at the Hunterston B power station before it ceased generating electricity in January 7, 2022.
5b. What role did the ONR have in the shutdown of Hunterston B. In other words, was this the recommendation of the ONR at the time? If not, what was the ONR recommendation.
6. Has the Torness nuclear power station had to be shut down for any length of time in the past five years, if so, please state the time periods and the clear reason for the shut down.
Information released
We confirm that under s.1 of the FOIA, we hold the information specified in your request. Please see below for a response to each of your questions in turn.
1. Can you please provide the latest safety case/criteria agreed by the ONR and EDF regarding the Torness nuclear power station.
Please find attached ONR’s Graphite Assessment Report of the safety case for Heysham 2 and Torness entitled EC 371321 / 371221 Long Term KWR Cracking Safety Case Graphite Assessment.
In our previous correspondence to you, dated 12 August 2025, we set out that we were considering the public interest test for the document identified in your request. This was in relation to the following exemption of the FOIA: s. 24 Safeguarding national security.
S.24 of the FOIA sets out the exemption from the right to know where the information requested is required for the purposes of safeguarding national security. It works to protect national security, which includes protection of potential targets. It allows a public authority not to disclose information if it considers releasing the information would make the UK or its citizens more vulnerable to a national security threat.
However, as s.24 of the FOIA is a qualified exemption, we are required to balance the public interest between disclosure and non-disclosure. We have therefore applied the public interest test and have set out factors for and against disclosure below.
Public Interest Test
Factors for disclosure:
- ONR is committed to being an open and transparent regulator. We will use openness and transparency to achieve our objective of developing and maintaining stakeholder trust in ONR as an effective independent regulator;
- The public have a vested interest in issues related to the nuclear industry, facilitating accountability and transparency; and,
- Issues related to the nuclear industry are subject to close scrutiny and debate, therefore there is a public interest in information related to nuclear activities and the release of such information.
Factors against disclosure:
- There is technical information contained within the ONR’s Assessment Report for Heysham 2 and Torness entitled EC 371321 / 371221 Long Term KWR Cracking Safety Case Graphite Assessment which is classed as UK Export Controlled Information (ECI). This information falls, as per the UK Strategic Export Control List, under code 0E001 ‘Technology according to the Nuclear Technology note for the development, production or use of goods specified in this category’ linked to 0C004 which covers graphite for nuclear reactor use. ONR is obliged to protect data that is classed as ECI for the purposes of nuclear non-proliferation and safeguarding national security.
- ONR would have no control over the onwards re-transfer of this ECI were it to be released.
- Adversaries or hostile actors can be highly motivated and may go to great lengths to gather separate pieces of intelligence to attempt to expose vulnerabilities. It would not be in the public interest for ONR to expose such vulnerabilities.
- Paragraph 13 of s.24(1) makes it clear that there need be no evidence that an attack is imminent for this exemption to be applied.
Conclusion
After careful consideration of the factors set out above, we have concluded that the specific information contained within ONR’s Graphite Assessment Report is classed as ECI for the purposes of nuclear non-proliferation and safeguarding national security. There is a strong public interest in safeguarding national security. The interests of national security should be given significant weight in the above factors against disclosure and outweigh the need for openness in terms of these specific types of information.
S.40 FOIA – Personal information
We have also removed some information from the attached document as it is personal data. This consists of names, job titles, and signatures. Release of each of this type of information could identify the individual either directly or indirectly. The personal data has been withheld using the exemption s.40(2) of the FOIA.
Release of the information would breach principle (a) of GDPR (lawfulness, fairness and transparency) on the grounds that there is no lawful basis to process this data. In addition, releasing this personal data would also breach principle (b) of GDPR (purpose limitation) as the data was provided for the purposes of internal report authorship and circulation.
1a. In particular, i am seeking information about what the new agreed safety criteria are for the cracks at the Torness nuclear power station that was agreed in May 2024. Can you confirm that this is the latest safety criteria that was agreed.
I can confirm that no new safety criteria were agreed in May 2024. Graphite inspections were conducted to confirm compliance with the current safety case.
2a. What has changed from the previous safety case criteria which was that supported operation up to that which was classed as "essentially intact" - which was as one with fewer than 10% cracked bricks.
EDF continue to successfully present a case that the reactor can be shut down and held down during a 1 in 10,000 year design basis seismic event. This position is supported by updated modelling and inspections.
2b. Can you provide the full safety case/criteria agreed that contained the reference to what was "essentially intact" as spelt out in 2a.
The previous safety case has been superseded by the safety case entitled EC 371321 / 371221 HYB/TOR Long Term KWRC Case. ONR’s Graphite Assessment Report of this safety case is attached to this response.
2c. Can you tell me when that safety case referred to in 2a was agreed.
ONR agreed to the implementation of the safety case in April 2024.
3. When was the last inspection of the Torness reaction cores, and at that point what were the estimated number of cracks that were found in both cores.
I can confirm that an inspection of Torness Reactor 1 was completed in March 2025; 16 fuel channels (128 bricks) were inspected and measured. An inspection of Torness Reactor 2 was carried out in May 2025; 13 fuel channels were inspected.
For context, this number of cracked fuel bricks does not challenge safety margins in the safety case, and we continue to have confidence in the licensee’s overall understanding of the graphite core ageing mechanisms.
The ongoing safety of operations at any nuclear site must be fully demonstrated to us as part of our ongoing regulation which is informed though our extensive inspection and assessment regime. As the independent nuclear regulator, we will not allow any plant to operate unless we are satisfied that it is safe to do so.
4. How many cracks were estimated in the Torness cores in or around April, 2024, but before May, 2024.
This would include ECI and therefore cannot be released in line with the Public Interest Test set out above.
5. How many cracks were found (estimated or otherwise) at the Hunterston B power station before it ceased generating electricity in January 7, 2022.
This would include ECI and therefore cannot be released in line with the Public Interest Test set out above.
End of generation was in November 2021 for reactor 3 (R3) and January 2022 for reactor 4 (R4).
5b. What role did the ONR have in the shutdown of Hunterston B. In other words, was this the recommendation of the ONR at the time? If not, what was the ONR recommendation.
The decision to shut down Hunterston B was EDFs commercial decision.
6. Has the Torness nuclear power station had to be shut down for any length of time in the past five years, if so, please state the time periods and the clear reason for the shut down.
Exemptions applied
s.24 and s.40
PIT (Public Interest Test) if applicable
Yes, included above.