You are viewing this website in an outdated browser. The site may not display correctly. Please upgrade to Microsoft Edge, Firefox or Chrome.


Step 3

Step 3 commenced on 15 November 2018 and involved deeper assessment of the design, primarily at a systems level, and of our arguments that support the safety, security and environmental features

The aims of Step 3 were to:

  • improve knowledge of the design for the UK regulators
  • progress resolution of any issues identified at Step 2
  • identify any significant design or safety case changes that may be required
  • assess the safety, security and environmental protection requirements
  • identify major issues that may prevent the UK regulators from issuing a Design Acceptance Confirmation (DAC) or Statement of Design Acceptance (SoDA) and attempt to resolve them
  • enable the Environment Agency to begin public consultation on its findings so far
  • achieve a significant reduction in regulatory uncertainty and greater acceptability of the design going forward.

As part of Step 3, we published the following draft documents:

As part of the GDA process, the public was invited to review and comment on the documents. Comments submitted before 25 October 2019 have been considered by ONR during their Step 3 assessment.

Some documents may contain commercially sensitive, export-controlled or sensitive nuclear information and so, in line with GDA guidance, we have made judgements on areas to be redacted prior to being made public.

In February 2020, the Regulators concluded that the information submitted by General Nuclear System Limited during Step 3 was sufficient to allow the start of Step 4.