US-based start-up Last Energy announced that its power plant design, the PWR-20, has completed a Preliminary Design Review (PDR) conducted by the UK’s Office for Nuclear Regulation (ONR), the Environment Agency, and Natural Resources Wales (NRW). ONR noted that Last Energy’s aspiration to receive a nuclear site licence decision by December 2027 could be achieved if Last Energy delivers the necessary submissions to the required standard and according to schedule.
In October 2024, Last Energy announced plans to deploy four microreactors in South Wales at a vacant site that housed the coal-fired Llynfi Power Station. The company obtained site control that month, followed by a US Export-Import Bank letter of intent for $103.7m to support the financing for the first installation, pending final commitment. In January 2025, Last Energy accepted a grid connection offer from National Grid Electricity Distribution (NGED) for 22 MW of export capacity and became the first microreactor developer to formally enter nuclear site licensing.
Completion of the PDR now equips Last Energy with tailored regulatory guidance as it moves into the next phase of regulatory assessment of the design, safety, security, and environmental cases. ONR said that, alongside the Environment Agency, it had completed a first-of-its-kind PDR on topics relating to the PWR-20 Nuclear Reactor Design and Last Energy UK’s organisational plans.
The review, which ran between February and June 2025, was conducted under the early engagement framework for new nuclear projects. The review examined three areas chosen by Last Energy: organisational plans and arrangements, environment and decommissioning, and safety analysis processes and maturity.
“As the first micronuclear developer to complete a Preliminary Design Review, we applaud the UK’s nuclear regulators for establishing a clear, flexible and direct regulatory pathway for micro-nuclear technologies to engage in nuclear licensing and environmental permitting,” said Michael Jenner, CEO of Last Energy UK. “Unlocking nuclear power at scale is essential to decarbonising the industrial economy and driving economic growth across the UK. Completing our PDR has provided essential guidance to efficiently undertake and complete licensing processes, positioning Last Energy to deliver the UK’s first commercial microreactor.”
Last Energy, founded in 2019, is a micro-nuclear technology developer that seeks to transform nuclear plants from complex construction projects into a mass-manufacturable product. The PWR-20, based on pressurised water reactor technology, produces 20 MWe, is fully modular, and designed for flexible siting, plug-and-play installation, and rapid scalability. Last Energy owns and operates its power plant on the customer’s site, bypassing the decade-long development timelines of electric transmission grid upgrade requirements.
“The Preliminary Design Review has built initial confidence that Last Energy understands regulatory expectations in those three areas and is planning to address them as the PWR-20 design matures and is subject to site-specific design assessment for deployment at their identified South Wales site,” ONR said.
