Citing terrorist threats, the Nuclear Regulatory Commission is performing a top-to-bottom review of the nation's 103 nuclear power plants. NRC Chairman Richard Meserve discussed the initiative Thursday in a speech at the National Press Club in Washington. Nuclear power plants, which produce 20 percent of the nation's energy, are "among the most formidable structures in existence and they are guarded by well-trained and well-armed security forces," Meserve said. After Sept. 11, security guards at nuclear power plants were given additional weapons, and patrols and posts were increased. "[There] is information that al Qaeda considers nuclear facilities potential terrorist targets," Meserve said. Each nuclear plant will undergo a security test called the "design-basis threat." While the details of the test are classified, Meserve outlined its elements. During the test, a group of commandos assault a nuclear power plant armed with automatic weapons, explosives and "incapacitating agents." The commandos are aided by someone on the inside and have a four-wheel drive vehicle armed with a bomb. Meserve said that power plants are defended with fences, access barriers, intrusion detection devices, heavily armed guards and armored defensive positions. Independent operators run the nation's nuclear power plants. These operators, or licensees, are responsible for plant security, which is regulated by the NRC. The NRC is reevaluating the design of the security test after admitting it was not sure what would happen if a "large airliner, loaded with jet fuel . . . crashed into a nuclear power plant," Meserve said. "There are limits…as to what should be expected from a private guard force," Meserve said. "[If] it were determined that nuclear plants should be defended against aircraft attack, I cannot conceive that the NRC would expect licensees or local law enforcement to acquire and operate anti-aircraft weaponry. Rather, this obligation would be one for the military." A group of Democratic lawmakers has drafted a bill, S. 1746, that seeks to federalize nuclear security workers, just as airport security workers were recently made federal employees. The NRC is "strenuously opposed" to this legislation, Meserve said. The NRC is clearly a regulatory agency and adding security to its responsibilities would muddy its mission, he explained. The NRC is also on alert for cyberterrorism, Meserve said. The agency took down its Web site following the Sept. 11 attacks because officials feared information contained in its pages could give terrorists know-how for future attacks. The site has been slowly restored with data, he said, though some remains offline.