Skip to content

Licensing of new reactors


ONR is responsible for licensing companies that wish to construct and operate new nuclear power stations at sites in Great Britain.
A site licence puts the licence holder under strict legal obligations and, importantly, gives wider and deeper regulatory powers to ONR to ensure the safe construction, commissioning, operation and eventual decommissioning of a nuclear site. The granting of a nuclear site licence is a significant step but is not itself permission to start nuclear-related construction. That requires a separate regulatory permission from ONR.


ONR provides regulatory advice and challenge to organisations intending to apply for a nuclear site licence. We also assess any subsequent application.

ONR needs to be satisfied that the applicant's choice of site is suitable; that it understands the hazards and risks of the activities that it proposes to carry out; and that it has a suitable schedule of safety submissions leading through to a pre-construction safety case. We place particular emphasis on the need to gain confidence that the applicant has the organisational capability to lead and manage for safety effectively. This means that we must be satisfied with the applicant's governance arrangements, resources, competencies and management processes before we can consider recommending that the Chief Inspector grants a licence.

Accordingly, a nuclear site licence for a new nuclear power station is only granted after a rigorous and robust process of assessment. Licence applicants need to understand ONR's licensing process and expectations and to engage with ONR in an open and transparent way in order to make efficient progress towards obtaining a licence.

Recent Projects

Sizewell C

In May 2024, ONR completed the assessment of an application from Sizewell C Ltd for a nuclear site licence to construct and operate two EPR reactors at Sizewell in Suffolk, adjacent to the existing Sizewell B station. Further information on the granting of a Nuclear Site Licence can be found in the ONR news section. 

The application and supporting documents are available on the NNB Generation Company (SZC) Ltd website.

Inactive Projects

Wylfa Newydd

In March 2017, Horizon Nuclear Power Ltd submitted an application for a nuclear site licence to construct and operate a Hitachi-GE Advanced Boiling Water Reactor (ABWR) power station at Wylfa on Anglesey. In January 2019, Horizon's parent company Hitachi announced the suspension of work on the Wylfa project. The resource that had been deployed by ONR on this project was subsequently diverted to other regulatory priorities.


ONR began engaging with NuGen Ltd in 2011 in relation to the company's intention to apply for a nuclear site licence to construct and operate a Westinghouse AP1000 Reactor power station at Moorside in Cumbria. In January 2019, NuGen announced that it was suspending work on its nuclear new build projects, and ONR's resources were subsequently redeployed onto other regulatory work.