Since Sept. 11, critics of the nuclear power industry have warned repeatedly that the nation's 103 atomic generating stations are vulnerable to terrorist attacks using hijacked airliners or smaller planes packed with high explosives.
Now, activists and watchdog organizations are pushing for countermeasures they say will improve safety and deter terrorist assaults from the air.
The U.S. government already has increased precautions against ground attacks on nuclear power plants, including California's two: San Onofre in northern San Diego County and Diablo Canyon on the Central Coast.
But environmentalists and nuclear-safety activists say the government has been far too slow in confronting the possibility of an air attack. At the same time, the Department of Justice and the Department of Homeland Security have continued to warn that Al Qaeda remains interested in targeting nuclear plants.
Critics of the industry point to a secret German government study leaked to the European media late last year. It suggests that nuclear plants may be more vulnerable than the U.S. Nuclear Regulatory Commission and power companies have maintained.
The critics have two concerns: A crashing jetliner might trigger the meltdown of a reactor core, or it could ignite fires in storage ponds for spent nuclear fuel at power plants. The concrete-and-steel pools contain some of the largest concentrations of radioactive material on Earth.
In late July, the Committee to Bridge the Gap, a California-based organization that has been a persistent critic of the nuclear power industry, formally petitioned the Nuclear Regulatory Commission, asking that it require the construction of barriers made from steel I-beams and cables that could deflect or stop an airliner from hitting a nuclear power plant. NRC officials say consideration of the committee's petition is pending.
Though he does not have firm estimates, the committee's founder, Dan Hirsch, said the beams, which would be spaced at intervals, could be put in place for about 1% of the $1-billion to $2-billion cost of building a power plant.
"Today, there is nothing to prevent an air attack," Hirsch said, "nothing except hope."
Steve Lloyd, vice president of regulatory affairs for the Nuclear Energy Institute, a trade organization and lobbying arm for the industry, countered that cages could cost far more -- $300 million to $500 million per power plant -- far too expensive for utility companies to build. The industry estimates are based on constructing geodesic domes to protect reactors, he said.
"Our basic position is that the plants are strong. They have redundant safety systems, and there is plenty of time to prevent the release of radiation," Lloyd said. "We don't see the need for very expensive actions."
The industry contends that environmental groups and critics of atomic power are using the threat of terrorism to further an anti-nuclear agenda.
"They are not doing this kind of thing for chemical plants," Lloyd said. "They want to make nuclear power so expensive there is no incentive to do it anymore."
If an airplane were to hit a nuclear power plant and emergency systems and evacuation plans proved inadequate, worst-case scenarios indicate that a reactor core meltdown or spent-fuel fire could result in hundreds of thousands of people killed or stricken with cancer or genetic damage. An area the size of Pennsylvania could be transformed into a no-man's land for centuries.
Such a disaster at the San Onofre Nuclear Generating Station, just south of San Clemente, could have devastating health and economic effects on many millions in the Southland. The Nuclear Regulatory Commission and the nuclear power industry have undertaken separate studies indicating a disaster of that sort is unlikely.
In interviews, regulators and industry officials said their faith in existing security measures is based partly on the fact that nuclear power plants are much smaller targets for a pilot to hit than the sprawling Pentagon and towering World Trade Center.
John Mazor, a spokesman for the Air Line Pilots Assn., agrees. Jetliners, he said, are difficult to maneuver with pinpoint accuracy and tricky to handle at very low altitude, as with the Pentagon attack. He said the Pentagon crash probably had more to do with luck than skill.
Even if an airplane smashed into a facility, NRC officials and plant operators said, a reactor core meltdown or catastrophic fire involving spent fuel in storage ponds is highly unlikely. Plants are built robustly and have emergency backup systems that can be activated quickly, they said.
Rather than spend time and money fortifying plants, NRC and industry officials say, the most cost-effective strategy to prevent air attacks on reactors remains continued improvements in airport and aircraft security.
The government has beefed up security for commercial airlines, improving passenger screening and armoring and locking cockpit doors.