The Nuclear Regulators have published guidance material on the Generic Design Assessment process for new nuclear power stations. These documents are aimed primarily at organisations intending to submit their reactor designs for assessment, but may also be helpful to other parties interested in the process.
An organisation wishing to carry out prescribed nuclear activities must apply for, and be granted, a nuclear site licence before it starts installation of a nuclear safety-related plant. A site licence puts the licence holder under strict legal obligations and, importantly, gives specific regulatory powers to ONR to ensure the safe construction, commissioning and operation of a nuclear site. For example a licence holder would typically have to request a consent from ONR to begin nuclear safety related construction.
Organisations wishing to construct and operate a new nuclear power station will need a number of environmental permits from the Environment Agency.
You can find guidance and application forms on GOV.UK :