Select committee: Public Accounts Committee
Conclusion 7
28th Report - Decommissioning Sellafield
Published 4 Jun 2025
Addressed to HM Treasury
Public Accounts Committee Decommissioning Sellafield All items in this report Report on parliament.uk ↗ Inquiry on parliament.uk ↗
Conclusion (the committee's words)
We heard from the NDA that the Magnox Swarf Storage Silo is “the most hazardous building in the UK”. It has been leaking radioactive water into the ground since 2018–we calculated, at current rates, enough to fill an Olympic–size swimming pool approximately every three years. The NDA accepted that this leak is its “single biggest environmental issue”. However, the witnesses told us that the radioactive particles are “contained” in the soil and do not pose a risk to the public.9 They also told us that they–and the site’s regulators–believe that the best way of 4 C&AG’s report, paras 13, 3.17, Figure 8 5 C&AG’s report, paras 1, 16, 3.7 6 C&AG’s report, Figure 7 7 Committee of Public Accounts, Nuclear Decommissioning Authority: risk reduction at Sellafield, Sixty–Fifth Report of session 2017 –2019, HC 1375, 31 October 2018 8 C&AG’s report, Figure 8 9 Qq 52–55 9 addressing the leak is to focus on emptying the silo.10 Sellafield Ltd expects that the silo will largely be emptied at some point between 2054 and 2059, which is 8–13 years later than it expected in 2018.11
From: Public Accounts Committee, 28th Report - Decommissioning Sellafield (HC 363), 4 June 2025
Government response
Latest Treasury Minutes progress report to the Committee of Public Accounts on the Twenty-eighth Report of Session 2024-26
The government responded to the whole report on 4 June 2026 (deadline 4 August 2025).
Treasury minutes: Government response to the Committee of Public Accounts on the Twenty-eighth report from Session 2024-26
Published 18 September 2025.
Summary written by Accountability Index from the government's response. It is not the government's own words.The government says it agrees with each of the Committee's recommendations covered in this extract, with target implementation dates ranging from December 2025 to March 2027, though some are already implemented and some publication details remain to be settled.
- On oversight (recommendation 1), the government agrees and describes the recommendation as implemented. Since January 2025 the department's Principal Sponsor chairs monthly performance meetings, and a review of the revised governance structure will be initiated within 2025-26.
- On medium-term targets (recommendation 2), the government agrees, with a target date of March 2027. Work "is required to establish how and then when this information would be made public", and DESNZ will commission an independent, externally led review of the NDA Group by end-2025.
- On asset management (recommendation 4), the government agrees and says the recommendation is implemented. It states that "Solely increasing the productivity of maintenance teams misses the demands" of the site's complex asset picture.
- On long-term cost scenarios (recommendation 5), the government agrees, with a target date of December 2026. It says "It will be necessary to agree the mechanism and timing, including what is published".