Professional Engineering

Dozens of engineers at the Office for Nuclear Regulation in Bootle, Merseyside, are coming towards the end of a quite staggeringly complex piece of work – the generic design assessment of the two reactors being considered for Britain’s proposed nuclear new-build programme.

The generic design assessment (GDA), which has been on-going for four years, has been a forensic examination of the Westinghouse AP1000 and Areva’s European Pressurised Water Reactor, establishing the safety case for both upfront before any construction has begun. The process has been extremely demanding, amounting to a total of around 50,000 working days and costing more than £50 million. 

But the Office for Nuclear Regulation (ONR) insists that it has been worthwhile, as it has resulted in scores of specific design changes to major components and systems such as control and instrumentation, which should ensure that any subsequent build process runs as smoothly as possible.

According to Kevin Allars, director for the nuclear build programme at ONR, the GDA has proved to be a logical and methodical approach to assessing new nuclear power station designs. He says: “It is about looking at the safety case upfront so that we can identify any issues that need to be addressed before it gets to the point where companies build them. 

“So when contracts are eventually placed for the reactors, there will already be a sense of regulatory approval for the designs being bought. It is about looking at things early in the process, and being open and transparent with the public and our stakeholders about what we are doing.”

The UK is alone in taking this type of approach to new nuclear construction – the GDA is a unique process that has never been done anywhere else in the world. Other countries pursuing nuclear new-build, such as France and Finland, have a staggered approval system where elements of construction can be carried out before the generic safety case is granted. But Allars is convinced that the UK approach makes more sense and should result in fewer delays when construction finally begins.

“The reactors being considered are new – they have not been run anywhere else in the world. So getting the safety case upfront, identifying issues and clearing them up, gives certainty to the designers, the operators, the vendors, and the regulators. And so far there have been no show-stoppers,” he says. 

“The operators have said to us that they believe the GDA is a good way of working – but the proof will be in a few years’ time. If they don’t have to make significant reactor design changes for regulatory needs, rather than any design changes they need to make for their own needs, then actually that will prove this process has worked like we believe it should have. 

“During the construction of what is Britain’s newest nuclear reactor in operation – Sizewell B – there were regulatory requirements that came along during the build phase that threw the project backwards. The GDA is good way of establishing some surety for regulatory requirements.”

The GDA began in August 2007 and has been characterised by a four-step approach, with each progressive technical assessment becoming more detailed. Transparency has been at the heart of the process, says Allars, with the ONR publishing extensive information relating to the reactor assessments, including technical reports, guidance, and regular updates on progress, and also allowing the general public to comment on its work.

Westinghouse, on the other hand, is yet to announce any confirmation of an operator who wants to buy its AP1000. Until such point, it is unlikely to progress its own application past the interim design acceptance stage.