The most recent large reactor design to complete the full GDA process is the UK HPR1000, also known as Hualong One. Developed by General Nuclear System Ltd for China General Nuclear and EDF, this ~ 1,075 MWe PWR combines active and passive safety systems within a double containment structure. The design entered GDA in 2017 and completed the process in 2022.
More recent GDA applications have been for small modular reactors( SMRs), which will be built in factories and assembled on site. The Rolls-Royce SMR design is a 470 MWe PWR with boron-free primary-circuit chemistry, significantly reducing tritium discharges. The design entered GDA in 2022 and has now progressed to Step 3( detailed assessment), which is expected to run until late 2026.
Holtec International ' s SMR-300 PWR design places the reactor vessel and major primary components inside a single pressure vessel within an underground containment structure, and relies heavily on passive safety systems for decay-heat removal. This 300 MWe design entered GDA in 2023, and began Step 2 of the revised two-step GDA framework in 2024. deployment, was accepted into GDA in 2024. Other designs are at the stage of early regulatory engagement. The Last Energy PWR-20 is a 20 MWe PWR designed for rapid factory manufacture and deployment in clusters. Moltex Flex is developing the FLEX 60 MWTh( Megawatt thermal) molten salt reactor using liquid fuel and integrated thermal storage. X-Energy ' s Xe-100 design is an 80 MWe high-temperature gas-cooled reactor using innovative TRISO( TRi-structural ISOtropic) coated particulate fuel and helium coolant. Two pool-type fast reactor designs are also under discussion – the 200 MWe Newcleo LFR-AS-200 uses molten lead coolant, and TerraPower ' s 345 MWe Natrium reactor is sodium-cooled.
The future of GDA Despite GDA, the UK remains the most expensive place in the world to build nuclear projects. In March 2026 the government announced it is fully implementing all recommendations of the Nuclear Regulatory Review 2025, including the simplification of safety cases and exercise of greater proportionality in the interpretation of ALARP and BAT. These reforms are expected to be completed by the end of 2027.
The GE Vernova Hitachi BWRX-300 started GDA in 2024, and became the first design to successfully complete the accelerated two-step process in 2025. It is a compact 300 MWe Boiling Water Reactor( BWR) derived from the Economic Simplified Boiling Water Reactor( ESBWR) design, further simplified for modular construction and with passive safety features.
Westinghouse ' s AP300, a smaller 300 MWe derivative of the AP1000 with similar passive safety features but designed for modular
ALARP and BAT The UK ' s health, safety and environmental legislation is founded on the key principle that those who create risks are responsible for managing them. Industry should reduce risk to be‘ as low as reasonably practicable '( ALARP). There is also a duty to make use of the ' best available techniques '( BAT) to protect the environment.
26 Radiation Protection Today www. srp-rpt. uk