Structure emerging for standard AP1000s

29 June 2011

British nuclear safety authorities have lifted the 'regulatory issue' status from their questions regarding the construction methods of Westinghouse's AP1000. Meanwhile, the company wants regional versions of the power plant to be as similar as possible. 


The pressurized water reactor uses a steel-concrete-steel sandwich technique for reactor building walls that should give it the strength required of a nuclear facility. However, building codes for the technique have never been established internationally, making it difficult for Westinghouse to define and justify the design of modules made in this way to UK and US safety authorities.


In the UK's Generic Design Assessment (GDA) process this had been officially noted by the Office of Nuclear Regulation (ONR) as an issue with the potential to block the deployment of the AP1000 if not addressed. This status was lifted on 27 June. In a letter to Westinghouse, the ONR noted that some "very challenging" work remained on the topic "that will require a high level of attention and resource," but that the remaining items should be resolvable in the normal course of the GDA process.


Westinghouse's managing director for the UK, Middle East and Egypt, Mike Tynan, said: "We recognise that there remains a considerable amount of work to be done on this and other aspects of the AP1000 design, but the lifting of the formal 'regulatory issue' today means that the safety inspectors recognise the fact we have made great progress in the area - demonstrating to them that the building structure is robust enough to withstand any credible accident and remain safe."


The eventual results of GDA should be Design Acceptance Certificates for AP1000 and the other reactor currently in the process, the Areva EPR. Utilities could combine these documents with site specific studies to create applications to build new reactors. EDF Energy is already preparing the ground for two EPRs at Hinkley Point, while two more are planned for Sizewell.


The GDA process was meant to have been completed this week, but extra time has been allowed to incorporate learning from the Fukushima accident, even though some technical questions seemed destined to be resolved separately from the main process due to the time constraint. GDA should now be complete by the end of the year. The aim of the UK government is to facilitate private replacement of a retiring nuclear fleet by about 2025 with the potential for significant long-term growth after that, subject to market forces.


In the USA, Westinghouse recently submitted documents intended to answer final questions from the Nuclear Regulatory Commission regarding a revision to the AP1000 building construction, as compared to a version certified in 2004. The goal is for the UK and US versions of the plant to be as similar as possible.


Meanwhile in China there are already four AP1000s under construction at Sanmen and Haiyang. These use the older design for the buildings, although forthcoming ones are to use the later one and would therefore match future UK and US units. China plans many more AP1000s with different degrees of involvement from Westinghouse and its partner, Shaw, gradually increasing the leadership of Chinese companies and engineers.


In America, site works are underway at the Summer, Vogtle and Levy sites towards two AP1000s each, while the first Chinese units should generate power during 2013. In the UK the AP1000 is being promoted to the Nu'Gen and Horizon Nuclear Power consortia while also being actively showcased in Lithuania for the Visaginas project. Also in the running for that is Hitachi-GE, with its ABWR design.


Researched and written
by World Nuclear News