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Introduction

It is normal practice for Accounting Officers to scrutinise significant policy proposals or plans to start or vary major projects and then assess whether they measure up to the standards set out in Managing Public Money. From April 2017, the government has committed to make a summary of the key points from these assessments available to Parliament when an Accounting Officer has agreed an assessment of projects within the government’s Major Projects Portfolio.

This Accounting Officer Assessment was made for the Small Modular Reactor (SMR) Programme, following the conclusion of the SMR Technology Selection Process and ahead of Great British Energy – Nuclear (GBE-N) entering into a Technology Partner contract with Rolls-Royce SMR. I have made the assessment as the Accounting Officer for the Department for Energy Security and Net Zero.

Background and context

The SMR Programme aims to support the deployment of SMRs in the United Kingdom, contributing to the government’s objectives on decarbonisation, energy security and economic growth. SMRs are expected to play a critical role in meeting future electricity demand alongside other low-carbon technologies, with the potential to enable a future fleet of reactors that supports system resilience, industrial capability and clean power generation.

GBE-N launched the Technology Selection Process in 2023 as a fair and competitive procurement exercise to identify a Technology Partner to deliver the United Kingdom’s first SMRs. Rolls-Royce SMR was announced as preferred bidder in June 2025, subject to final government approvals and contract signature. At the Spending Review 2025, the SMR programme was allocated £2.6 billion across the Spending Review period to enable delivery.

The Technology Partner contract is structured in two stages. Stage One focuses on site-specific design for three units at Wylfa, while Stage Two would cover construction, supply, installation and commissioning, subject to a positive Final Investment Decision and further business case approval.

Regularity

A key aspect of the regularity test is whether the proposal is affordable and has the necessary legal and Treasury authority.

GBE-N has statutory underpinning through the Energy Act 2023, which provides a clear legal basis for entering into the Technology Partner contract.

HM Treasury has authorised GBE-N to enter into the contract. Funding for the programme has been agreed at Spending Review, with sufficient resource provision across the Spending Review period to progress Stage One of the contract. Further funding will be sought at future Spending Reviews.

Legal risks, including procurement law risks, have been assessed prior to entering into the contract. No material subsidy control risks have been identified in relation to award of the contract.

Overall assessment: My assessment is that the regularity test is satisfied.

Propriety

The Technology Selection Process has been conducted as a fair and competitive procurement exercise, launched in 2023 and resulting in the selection of Rolls-Royce SMR as preferred bidder in June 2025. The proposal has been subject to appropriate governance and assurance due to its inclusion on the Government Major Projects Portfolio.

An overarching Programme Business Case has been approved through departmental governance and by the Chief Secretary to the Treasury. A Full Business Case for the Technology Selection Process was submitted to the Major Projects Review Group in October 2025, and the Chief Secretary to the Treasury authorised contract signature subject to pre-conditions being met (since completed).

GBE-N operates under established governance arrangements, with its Chief Executive designated as Accounting Officer for the GBE-N accounts and personally responsible for safeguarding public funds. The GBE-N Board, including a new Chief Executive (as of March 2026) and substantive Non-Executive Directors, is responsible for ensuring effective governance, risk management and internal controls.

Overall assessment: My assessment is that the propriety test is satisfied.

Value for money

The value for money appraisal follows HM Treasury Green Book guidance and the Department’s Nuclear Value for Money Framework, taking account of both monetised and non-monetised costs and benefits of the SMR Programme.

The economic case is informed by the Department’s power system modelling. Initial modelling outputs, updated once the preferred bidder stage of the SMR competition had been reached, suggest the project represents positive marginal value for money to the system with adjustments for uncertainty, risk and optimism bias applied. This modelling sits alongside the non-power system benefits, which include the potential to support ~3,000 jobs on site at peak construction, stimulating regional growth at the site and factory locations. These wider benefits are expected to be significant but are not fully captured in quantified system modelling. Overall, the result is a robust value for money case for the SMR programme.

Material risks have been considered, including the first-of-a-kind nature of the selected Rolls-Royce SMR technology, and cost uncertainty associated with early project maturity. Mitigations include the contractual structure and on-going programme assurance. Failure to proceed to enter the Technology Partner contract would likely result in a delay of two to three years to re-run a procurement, the loss of incurred costs, and damage to market confidence in the United Kingdom nuclear sector.

Overall assessment: My assessment is that the value for money test is satisfied.

Feasibility

GBE-N has established the necessary structures, project controls and cross-disciplinary teams to deliver the contract, including an Intelligent Client function with dedicated commercial and finance expertise, a comprehensive Contract Management Plan, and robust governance arrangements. The contract is structured around staged delivery, regular Gateway Reviews, performance-based incentives, and active risk and change management.

The project sits on the Government’s Major Projects Portfolio and is subject to regular assurance reviews.

Key risks include the availability of suitably qualified nuclear personnel, GBE-N’s continued ramp-up of capability, Rolls-Royce SMR’s transition into detailed design and delivery, and planning and consents risk. Each is supported by an active mitigation strategy.

All pre-conditions, set by the Major Projects Review Group and to be met ahead of contract signature, have been addressed. The Department’s Commercial Assurance Board and the Government Chief Commercial Officer have confirmed they are content with the final contract terms.

Overall assessment: My assessment is that the feasibility test is satisfied.

Conclusion

As the DESNZ Accounting Officer I have considered the assessment of the SMR Programme – Technology Partner Contract and approved it on 8 April 2026. I have prepared this summary to set out the key points which informed my decision.

If any of these factors change materially during the lifetime of this project, I undertake to prepare a revised summary, setting out my assessment of them.

The summary included in this letter will be published on the government’s website (°Ç¸ç³Ô¹Ï). Copies of this letter will be deposited in the Libraries of the House of Commons and the House of Lords, and sent to the Comptroller and Auditor General and Treasury Officer of Accounts.

Jonathan Brearley
Permanent Secretary, Department for Energy Security and Net Zero