Aircraft threat to nuke plants debated
By Scott R. Burnell

06/17/2002
United Press International Science News
From the Science & Technology Desk
Published 6/17/2002 8:07 PM

WASHINGTON, June 17 (UPI) -- A report from Sandia National Laboratories, expected by the end of this month, will show nuclear reactor containment buildings can withstand a hit from a commercial airliner, a nuclear industry spokesman said Monday.

The report models the reaction of various parts of a containment building to head-on impacts from both the engines and fuselage of fully loaded planes, including the Boeing 767, said Stephen Floyd, senior director for regulatory reform at the Nuclear Energy Institute. The report is separate from a Nuclear Regulatory Commission effort, but both were commissioned after the Sept. 11 attacks, Floyd told reporters at a National Press Foundation briefing.

"We're completing the assessment right now. It should be ready by the end of this month," Floyd said. "We were not able to get the aircraft to penetrate the containment (in the simulations). We thought the engines might be one part that got in ... but as it turns out, the (engine shaft) is hollow and it pretty much telescopes on impact."

The report considered the different thicknesses of concrete throughout a containment building's walls, as well as how the structure's curved top could deflect an aircraft, Floyd said. The report also indicates the buildings covering the pools that cool spent nuclear fuel would also stand up to an airliner's impact, he said.

Not all nuclear experts agree with this assessment, however.

The NEI study seems to underestimate a terrorist's capabilities to push an airplane past its design limits, a dangerous assumption after the World Trade Center attacks, said Edwin Lyman, president of the Nuclear Control Institute, an organization critical of the industry's commitment to safety. Computer simulations run by NCI last year suggest engines could penetrate a containment vessel, he told the briefing.

"I would like to see the experimental data demonstrating the engine shafts telescope," Lyman said. "All that aside, the containment building is not the most vulnerable part of the plant."

The impact and fire from a airliner crash could disable a reactor's cooling system to the point where the nuclear fuel would overheat, Lyman said, causing a "meltdown" where the molten fuel escapes the building and contaminates the environment.

A jet fuel fire would burn out too quickly to damage enough equipment for such a scenario, Floyd responded, and reactors have redundant firefighting and cooling systems in any case.

The fire-suppression plans at some reactors are suspect, said David Lochbaum, a nuclear safety engineer with the Union of Concerned Scientists. Some plants have layouts that place primary and backup firefighting systems in adjacent rooms, leaving them vulnerable to simultaneous failure in the event of a crash, he told the briefing.

Despite the Bush administration's announcement about uncovering a plot to explode a "dirty bomb" containing radioactive material other than nuclear fuel, reactors still should be considered prime terrorist targets, Lyman and Lochbaum said. Spent fuel has a varied set of elements far more dangerous than medical or industrial radiation sources, Lyman said. Security officials also should consider the possible public reaction to even a failed attack on a reactor, Lochbaum said.

The terror value of a reactor incident aside, Sept. 11 itself demonstrated attackers placed higher value on other targets, Floyd said. The flight paths of several of the hijacked planes that day came close to many reactors without attempting to crash into them, he noted.

Entergy's Response

Based on our engineering judgment, neither a large aircraft nor aircraft engines could penetrate the steel-reinforced concrete and steel inner liner of the reactor containment structures. The walls are 3_ to 4_ feet thick, and are designed to resist and disperse the impact. The aircraft itself would fold like an accordion and further disperse the impact.

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