Westinghouse pauses at end of UK reactor generic design approval process

15 July 2011

The UK nuclear regulator has published results of most of the final step of a generic design assessment of the EDF/Areva EPR reactor and the Westinghouse AP1000 reactor design.

Until March, the UK regulator had planned to publish interim approvals-in-principle of both designs in June, with a list of issues that need resolution to achieve final approval. After the Fukushima Daiichi event, however, this goal was pushed back to the end of the year to take into account the final Fukushima Daiichi lessons learned report from chief regulator Mike Weightman, scheduled for publication in September.

The informal end of the GDA process finds two reactor vendors in very different positions. The EDF/Areva team is in such a hurry to start building that it has already started talks with the regulator to prioritise solving outstanding regulatory items that might affect contracts and early site works at its Hinkley Point site in Somerset (although EDF has still not made a final investment decision to go ahead). Westinghouse, on the other hand, still has no confirmed customer for its AP1000 reactor, and has told the regulator that although it will incorporate Fukushima lessons to achieve an interim DAC by the end of the year, it will not begin to resolve any outstanding issues until it has secured funding for the work. That decision means that the UK regulator will start to move technical staff previously assigned to review Westinghouse materials to other tasks.

Now, the UK regulator has published a list of the remaining outstanding issues with both reactor designs, and, where available, plans from the vendors that it believes are credible to solve those issues. The only GDA issue left out is their response to the lessons of Fukushima Daiichi.

The EPR reactor has a total of 31 GDA issues; the AP1000 reactor has 51. However, Kevin Allars, director for nuclear new build, warned people not to draw any conclusions about which design is farther along than which, since GDA issues are not necessarily the same magnitude. He was speaking at the UK NIA's Nuclear New Build 2011 conference in London in early July.

Outstanding EPR issues, all of which have resolution plans considered to be credible by the regulator, are published on www.hse.gov.uk/newreactors/2011-gda-issues-epr.htm. Outstanding AP1000 issues, most of which (46 of 51) have resolution plans considered to be credible by the regulator, are published on www.hse.gov.uk/newreactors/2011-gda-issues-ap1000.htm.

Even once all of the issues are resolved and a design acceptance confirmation is received, the reactors will still need a site licence before nuclear concrete can begin, as well as other planningĀ approvals. Once that latter step begins, the regulator has committed not to reinvestigate matters already covered by the GDA process.

The regulator said that there are no show-stopping problems for either design. An issue that potentially threatened regulatory approval of the AP1000, about the innovative steel-concrete-steel structure of the shield building and internal modules, was closed on 27 June.

The UK regulator originally raised an issue with the steel-concrete-steel engineering design in February 2010. Then, the regulator's position had been that the building codes Westinghouse had based the design on, American Concrete Institute 349-01, did not in fact cover what Westinghouse was planning, that the substantiation document that Westinghouse submitted was incomplete and outdated, and therefore that Westinghouse needed to justify the use of the design. Finally, Westinghouse had agreed with the US regulator to make some changes in the shield building design, so the UK regulator required it to review how the changes might affect other steel-concrete composite structures in the design.

In the closure letter, the regulator said that Westinghouse had performed sufficient confirmatory analyses, calculations and lab testing to satisfy their concerns. First, although structural elements are still sized to ACI-349-01, Westinghouse has also referenced other design codes which demostrate that the structure has considerable safety margin, the regulator said. Second, Westinghouse confirmed that each type of steel-concrete structure, the shield building and civil modules, will actually be built in different ways, and specified detail. Third, Westinghouse demonstrated that there is still sufficient safety margin in the structure after it down-rated the margin of some elements to reflect the fact that the design codes weren't fully applicable to nuclear power.

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