Over the past five years, the UK’s nuclear output has been relatively stable but not growing. In 2022, nuclear power accounted for about 15 percent of the nation’s electricity generation.

As the UK embarks on an ambitious expansion of its nuclear energy programme, the sector faces a complex blend of ageing infrastructure, high-cost new builds, regulatory challenges, and long-term waste-management debates.

Has output risen or declined over the past five years? Over the past five years, the UK’s nuclear output has been relatively stable but not growing. In 2022, nuclear power accounted for about 15 percent of the nation’s electricity generation, roughly 47.7 TWh out of 324 TWh (World Nuclear Association, 2023; House of Lords Library, 2023). That share has remained consistent at around 13–15%, reflecting both the gradual retirement of older reactors and limited commissioning of new capacity (UK Government, 2023).

As noted, nuclear contributes approximately 15% of the UK’s electricity mix, based on 2022 figures (World Nuclear Association, 2023).

Sources of nuclear power in the UK – The current fleet comprises: Four Advanced Gas‑cooled Reactor (AGR) sites: Heysham 1 & 2, Hartlepool, and Torness; One Pressurised Water Reactor (PWR): Sizewell B (UK Government, 2023). These plants supply around 6 GW of capacity.

Costs are significant for new builds: Hinkley Point C: Constructed since 2017, now estimated at £41–48 billion (2024 prices), with commissioning expected between 2029–2031 (EDF, 2024); Sizewell C: Final investment decision approved in July 2025, with a projected cost of £38 billion. Expected construction time spans 9–12 years, delivering two EPR reactors (Sizewell C Consortium, 2025); EDF is investing £1.3 billion (2024–26) to sustain existing stations and fund life extensions (EDF, 2024).

Reactor technology and modernity

The UK’s legacy fleet (AGR and Sizewell B PWR) is ageing but receiving life-extension investments (UK Government, 2023). New reactors (Hinkley Point C and Sizewell C) use European Pressurised Water Reactor technology, offering advanced safety and long operational lifetimes (\~60 years). Small Modular Reactors are in the planning stages, expected online by the 2030s, promising modular construction and cost-efficiency (House of Lords Library, 2023).

Construction timelines

Hinkley Point C: Construction began in 2017, now expected to be operational by 2029–31 after delays and cost overruns (EDF, 2024); Sizewell C: Preliminary works began around 2023; full construction timeline is 9–12 years to commissioning (Sizewell C Consortium, 2025); SMRs: Design and selection under way, with deployment projected in the mid‑2030s (UK Government, 2023).

The Office for Nuclear Regulation oversees safety, licensing, and regulation of nuclear plants. Decommissioning and waste management fall under the Nuclear Decommissioning Authority, a public body tasked with carrying out safe decommissioning and managing waste funds (NDA, 2023).

Waste disposal and radioactive waste management

Low-level radioactive waste is stored at the Low Level Waste Repository near Drigg, managed by the NDA (NDA, 2023); the High-level waste strategy centers on developing a Geological Disposal Facility. However, the Treasury has deemed the current plan “unachievable,” with cost projections between £20–54 billion and decommissioning extending to 2150 (The Guardian, 2025); A mid-term shallow disposal facility (up to 200 m deep) could be operational within about 10 years, potentially cutting costs by £500 million and accelerating decommissioning processes (UK Government, 2025); Innovative waste practices are also being promoted, including isotope recycling for medical/diagnostic use, aiming to reduce waste volume and environmental impact (UK Government, 2025).

The UK’s nuclear programme sits at the intersection of necessity and controversy. On one hand, the government is committed to achieving net zero by 2050, and nuclear is positioned as a low-carbon, reliable baseload source to complement intermittent renewables. On the other hand, escalating costs and project delays (notably Hinkley Point C) undermine public confidence, while unresolved waste management continues to spark environmental concerns.

Critics argue that nuclear is prohibitively expensive compared to wind and solar, both of which have seen falling costs. Proponents counter that nuclear’s reliability justifies the investment, particularly in an energy system vulnerable to volatility and foreign dependence on gas. The introduction of SMRs may shift the balance by reducing construction times and capital costs, though these technologies remain unproven at scale.

In terms of waste, the UK’s failure to finalise a Geological Disposal Facility reflects the broader global challenge of long-term nuclear stewardship. While shallow disposal and recycling offer stopgaps, the debate underscores the tension between nuclear energy’s low-carbon credentials and its unresolved legacy of waste.

This Post was submitted by Climate Scorecard UK Country Manager, Cesar A. A. Da Silva. 

References:

House of Lords Library (2023) The role of nuclear in the UK’s energy supply. Available at: (https://lordslibrary.parliament.uk/the-role-of-nuclear-in-the-uks-energy-supply/) (Accessed: 18 August 2025).

Nuclear Decommissioning Authority (NDA) (2023) Annual Report and Accounts. NDA. Available at: (https://www.gov.uk/government/organisations/nuclear-decommissioning-authority) (Accessed: 18 August 2025).

Sizewell C Consortium (2025) “Final investment decision for Sizewell C”. Available at: (https://www.sizewellc.com/](https://www.sizewellc.com/ ) (Accessed: 18 August 2025).

 

UK Government (2023) Civil Nuclear Roadmap to 2050. Department for Energy Security and Net Zero. Available at:(https://www.gov.uk/government/publications/civil-nuclear-roadmap-to-2050 ) (Accessed: 18 August 2025).

UK Government (2025). Updated approach to managing nuclear waste. Department for Energy Security and Net Zero. Available at:(https://www.gov.uk/government/news/updated-approach-to-managing-nuclear-waste ) (Accessed: 18 August 2025).