The Toshiba-Westinghouse AP1000 reactor remains a symbol of the U.S. nuclear future to supporters and opponents alike.

If the Nuclear Regulatory Commission grants required approvals, the reactor, with its "passive" safety engineering, would be installed at the Vogtle nuclear station in Georgia as the first new unit built in the United States in a generation. Other utilities have selected the modified Westinghouse design for planned or proposed new plants.

Foes of a U.S. nuclear power revival continue to fight the AP1000 and have seized on a statement from NRC last week that cited new issues in the agency's design review -- a review that industry officials had assumed was going smoothly toward a final decision this year.

The issue arose last week at a meeting between Westinghouse and NRC staff that included issues of emergency stresses on the reactor shield building, such as during an earthquake, said NRC spokesman Scott Burnell. "Westinghouse discovered they had missed an item on the to-do list regarding loads on the sides of the water storage tank," he said.

Burnell referred to the water reservoir above the shield building that floods the reactor containment area if normal reactor cooling systems fail. Gravity, not pumps, delivers the water. NRC had required Westinghouse to retest the strength of the unit using a more demanding standard, Burnell said, but the company had neglected to do so.

NRC Chairman Gregory Jaczko suggested Friday that the AP1000 design review could be delayed. "Westinghouse must resolve the issues before we can consider finalizing NRC certification of the design. The agency will determine what impact this effort may have on the schedule of the AP1000 design amendment and related license application reviews after the staff examines the company's response on these matters."

Westinghouse said in a statement Friday that it was "confident in the AP1000 design and its passive safety features, as it is one of the most studied, reviewed and analyzed nuclear power plant designs in the history of the commercial nuclear power industry." The company said it will continue to work with NRC "as part of the normal licensing process to address the few remaining confirmatory items, none of which are safety significant and several of which are self-identified by Westinghouse."

Jaczko seemed to anticipate criticism from some Republicans in Congress who have expressed impatience with the pace of NRC safety reviews. "The NRC will always place its commitment to public safety and a transparent process before any other considerations," Jaczko said.

Rep. Edward Markey (D-Mass.), a vocal opponent of nuclear power, saw Jaczko's statement as a welcome response to his concerns about the ability of the AP1000 to survive a major earthquake, hurricane or earthquake strike, and as evidence of NRC's closer scrutiny of safety issues following the Fukushima Daiichi nuclear accident. Markey also renewed his insistence that NRC heed warnings by its staffer John Ma about the ability of the reactor containment structure to withstand earthquake or aircraft impact forces.

"In the wake of the Fukushima meltdown, the NRC also should suspend all of its licensing decisions on new designs, new reactors or relicense applications until it incorporates the lessons of the Japanese catastrophe into its plans and regulations," Markey said.

'Multiple issues of attention to detail'

Burnell said, however, that Friday's NRC statement was unrelated to Ma's concerns, which were not adopted by the NRC reviewers. And the statement had "zero" to do with the Fukushima accident, he added.

In addition to the missed testing procedure, NRC has other questions about Westinghouse's follow-through in the design review, Burnell said. "None of these issues represent a gaping hole in the application or in the supporting information. But given that there are multiple issues of attention to detail, this does represent something that the NRC considered important enough to issue a statement."

Another AP1000 critic, Jim Warren of NC WARN, was not convinced that Friday's announcement marked a major new challenge to the reactor's design. "The NRC statement is so heavily couched, it's as if they are bending over backward to say the project won't be delayed and they can pretend they will stay on schedule."

The safety issues about the AP1000 design raised by NC WARN and other critics include whether corrosion could lead to a breach in the primary containment and a radioactivity release to the atmosphere through the open top of the shield building.

Another issue for critics is whether the water delivered from the elevated reservoir in an emergency would continue to cool the reactor if there were a sustained loss of power for emergency pumps. Critics also contend that the recirculation of cooling water around the containment structure could be obstructed by debris on filtering screens in the unit. These issues have been before NRC reviewers for many months and have not halted the review.

NRC's Atomic Safety Licensing Board noted a number of accident scenarios that could challenge cooling water recirculation, in a December 2010 letter to Jaczko. But the ASLB said tests of the design had resolved these concerns. "The AP1000 design, therefore, meets the regulatory requirements" for long-term cooling during an anticipated design basis accident, it said.

The Fukushima accident has produced "a mountain of data" on safety issues that should be considered by the NRC staff reviewing the AP1000, Warren said. But critics may have to rely on the courts, not the NRC, to make their protests stick, he said.

Reprinted from Climatewire with permission from Environment & Energy Publishing, LLC., 202-628-6500