The US Nuclear Regulatory Commission has told Westinghouse that the proposed design of the shield building for its AP1000 nuclear power plant will require design modifications and testing to demonstrate that it will perform its intended safety function under design basis loads.

As the name implies, the AP1000 shield building would protect the reactor’s primary containment from severe weather and other events. The building’s other functions would include providing a radiation barrier during normal operation and supporting an emergency cooling water tank.

The Westinghouse AP1000 design received certification in the USA in January 2006, however later that year as part of the Bellefonte combined license (COL) application Westinghouse told the NRC that it would be submitting additional technical reports. The reports included, among other things, standard design changes that are a result of the AP1000 detailed design efforts.

Those design changes include a redesign of the pressurizer, a revision to the seismic analysis to allow an AP1000 reactor to be constructed on site with rock and soil conditions other than the hard rock conditions certified in the AP1000 DCR, changes to the instrumentation and control (I&C) systems, a redesign of the fuel racks, and a revision of the reactor fuel design

In a statement Westinghouse said that it “fully expected” that the NRC would require additional analysis, testing or actual design modifications to the shield building.

“In fact, we had already begun to address certain portions of the design. We have fully committed the resources necessary to both quickly and definitively address the NRC’s concerns, and we are confident that we will meet all applicable requirements.”

The firm said that its goal is to receive Design Amendment Certification from the NRC in 2011, and that it will continue to work to bring the first AP1000s online in the USA in the 2016 timeframe.