The Generic Design Assessment (GDA) process has officially begun for X-energy's Xe-100 advanced modular reactor in the United Kingdom. This decision comes one year after Centrica and X-energy Reactor, a subsidiary of X-energy LLC, signed a Joint Development Agreement to deploy Xe-100 advanced modular reactors in the UK. The companies have identified the Hartlepool site, owned by 
EDF and Centrica, as the preferred location for the first of a planned UK fleet, which could total up to 6 GWe.
The GDA is a voluntary process where the UK's nuclear regulators—the Office for Nuclear Regulation (ONR), Environment Agency, and Natural Resources Wales—evaluate the safety, security, and environmental aspects of new reactor designs intended for deployment in Great Britain. This assessment is separate from site-specific applications. Successful completion of the three-step GDA results in a Design Acceptance Confirmation from the ONR and a Statement of Design Acceptability from the Environment Agency. The ONR stated that the GDA will proceed once necessary arrangements regarding timescales and resources are finalized.
X-energy UK Holding Ltd is also engaged in a Tier 3 Preliminary Design Review with UK regulators, focusing on specific aspects of the Xe-100 design. X-energy submitted its application for GDA entry in June. The GDA process, expected to take approximately three years, formally initiates the assessment of the design's suitability for deployment and operation, preceding the technical and environmental evaluations required for site-specific licensing and permitting.
The submission is anticipated to leverage the Xe-100's licensing progress in the USA and benefit from increased collaboration between UK regulators and the US Nuclear Regulatory Commission (NRC). This collaboration aims to integrate NRC-reviewed design documentation and safety analyses into the UK design reviews. The NRC has been involved in pre-application activities with X-energy since September 2018.
Over the past year, the partners have conducted early project activities, including formal Early Engagement with UK nuclear regulators and the submission and acceptance of the Xe-100 into the GDA process. They have also submitted a proposal for inclusion in the UK Government's Advanced Nuclear Pipeline, a register of privately led advanced nuclear projects in England or Wales deemed mature and credibly deliverable in the UK, subject to regulatory and government approvals. The results of this submission are expected soon.
X-energy CEO Clay Sell highlighted the company's progress in fleet-scale deployment across the Atlantic, emphasizing the importance of a strong regulatory foundation for efficiency from the first project to a full commercial fleet. Centrica CEO Chris O’Shea noted the partnership's progress, stating that deploying advanced nuclear technology at scale, with up to 6GW of new capacity across the UK, will enhance energy security, create economic value, and generate skilled jobs. The partnership has engaged specialist firms for site studies and planning, and has collaborated with local bodies in Hartlepool to support workforce development and training, including the launch of a new Nuclear and Electrical Trades Academy.
The Xe-100 is a Generation IV advanced reactor design, producing 80 MW of electricity or 200 MW thermal. A standard 'four-pack' configuration can achieve a total power output of 320 MWe, scalable to up to 12 units per site. The reactor uses tri-structural isotropic (TRISO) particle fuel, which offers safety benefits due to its high-temperature resistance without melting, and can provide both electricity and process heat. X-energy is also developing its initial Xe-100 plant in the USA with Dow Inc. on the Texas Gulf Coast, and another plant with Energy Northwest in collaboration with Amazon, planning up to 12 units near Energy Northwest's Columbia Generating Station in Washington State.