Office for Nuclear Regulation

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Generic Design Assessment (GDA)


ONR is responsible for providing a systematic design assessment of potential new reactor designs planned for operation in the UK.

GDA is a joint process undertaken by the ONR and the Environment Agency. The regulators get involved with nuclear reactor design companies at the earliest stage where they can have the most influence. The process focuses purely on the reactor design and does not consider any site specific issues. The regulators will only conduct GDA on a new power station design following a request from the government.

The regulators undertake a technical assessment of the submissions provided by the design companies and provide advice about any issues they identify, thus allowing issues to be resolved at the design stage. This approach increases regulatory effectiveness and efficiency and helps developers reduce their commercial risks on costs and timescales. The process is systematic and contains a number of steps, with the assessment getting increasingly detailed as the process develops.

The process is open and transparent.  The regulators publish reports at the end of each step, which provide an update on the assessment and highlight any concerns or technical issues that have been raised. This means that anyone can view the detailed design information, and have the opportunity to comment on it via the GDA comments process.

Current activities

ONR and the Environment Agency are currently assessing two reactor designs:

Hitachi GE's UK Advanced Boiling Water Reactor (UK ABWR)

This reactor is currently in step 4 of the GDA process. ONR completed step 3 and published a suite of assessment reports and a summary report in October 2015.

General Nuclear System's UK HPR1000

The reactor is currently in step 1 of the GDA process.

Westinghouse's AP1000 Reactor Design

The GDA of AP1000 formally re-mobilised in August 2014 after a pause in the process. The reactor is now in the closure phase of GDA, resolving the outstanding issues to the regulators' satisfaction before Westinghouse can formally complete the GDA process.

Further information (including on the comments process) can be found on the GDA website.