Slow responses from plant vendors have impeded generic design assessments (GDA) of two nuclear reactor types vying for the U.K.’s potentially large “new build” program. In an interim report released on Nov. 7, the U.K. Health & Safety Executive (HSE) lists inadequate submissions in support of the Westinghouse AP1000 and Areva’s EPR reactors.

“If we are to complete GDA on time, we need the design companies to work with us and provide the high-quality and timely information we need,” says Kevin Allars, HSE’s director of the assessment.

HSE is scheduled to complete the GDAs in June 2011 after 42 months of work. The first plants are planned to start operations seven or eight years after that.

While HSE declares both reactor designs potentially suitable, “There is still a significant amount of detailed assessment work for us to do,” reports Allars.

In the next and final phase, the GDA will move from “a questioning and information exchange to one of clarifying issues and resolving them,” Allars says.

On the EPR’s control and instrumentation submissions, HSE reports “significant concerns about the complexity of the architecture and on the very high reliabilities [being claimed].”

For both reactor submissions, HSE officials note the lack of evidence that the civil structural designs conform to required standards. In Westinghouse’s case, “This is particularly true for the novel steel-concrete-steel sandwich modular construction proposed,” says the report.

HSE also complains about Westinghouse’s use of imperial rather than the required metric units. On mechanical issues, “Westinghouse has made minimal progress in addressing our concerns,” reports HSE.