The Nuclear Regulatory Commission (NRC) on Tuesday certified an amended version of the Advanced Boiling Water Reactor (ABWR), the third-generation reactor design offered separately by GE-Hitachi and Toshiba, which has been chosen for new nuclear builds at the South Texas Project (STP) site. The NRC’s decision means that nuclear developers in the U.S. can use the reactor in proposed projects.

The NRC had certified the original ABWR design in 1997, but the regulatory agency has since taken several steps to improve security at existing nuclear power plants, including adopting a rule in March 2007 that requires both existing and potential new reactors to defend against a more realistic threat. The agency also issued a February 2002 order requiring all existing nuclear power plants to develop and adopt strategies to cope with large fires and explosions from any cause, including potential aircraft impacts. In March 2009, the NRC updated that rule, codifying these requirements for all existing and future nuclear power plants.

The final rule, which will become effective as soon as it is published in the Federal Register, amends the ABWR’s design certification to address the effects of the impact of a large commercial aircraft. STP Nuclear Operating Co. (STPNOC), a firm that has proposed to expand the STP with two new ABWRs, had submitted an application to the NRC to amend the design in June 2009.

“The rule certifies that STPNOC’s option for the ABWR design has appropriately accounted for aircraft impact effects. This means that following such an impact, only minimal operator actions would be necessary to meet two conditions: a) the reactor core remains cooled or the containment remains intact; and b) spent nuclear fuel cooling or spent fuel pool integrity is maintained,” the NRC said in a statement.

The rule’s final approval comes even though NRG Energy, majority owner and operator of STP, has said it would stop investing in the multibillion-dollar project to build new ABWRs at the site in Matagorda County, Texas. NRG and Toshiba American Nuclear Energy Corp., its partner in Nuclear Innovation North America (NINA), had earlier this year also said they would halt all detailed engineering work and other preconstruction activities and cut the project workforce. With NRG no longer funding the new reactor project, Toshiba has reportedly been moving the process forward at the NRC. It is unclear what NINA plans for the proposed project.

The NRC is also expected to certify Westinghouse Electric’s amended AP1000 reactor design soon. Southern Co. and SCANA Corp. have proposed to use the AP1000 at plants in Georgia and South Carolina. Toshiba is the majority owner of Westinghouse.

Toshiba, along with GE-Hitachi, designed the Generation III ABWR (for more on the history of this and related reactor technologies, see “The Evolution of the ESBWR” in POWER’s November 2010 issue) and it has built two of four ABWR units already commissioned in Japan.

Sources: POWERnews, NRC, Toshiba, POWER