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Nuclear power plants in the age of terrorism: Safer than many think

By Gerald E. Marsh and George S. Stanford
web posted November 19, 2001

Nuclear reactorAnxiety over a potential terrorist attack on a nuclear power plant has been frequently expressed in recent days. But is this source of abundant, environmentally-friendly energy an attractive target for terrorists?

Not really.

The greatest danger could well be panic caused by sensationalized reporting, not radiation.

Let's look at the worst terrorists could do.

The crash of a large airliner into a reactor is on everyone's mind. A reasonable speculation is that a direct hit by one of the heavy engines (requiring incredibly precise aiming by the pilot) could split the nuclear plant's reinforced concrete containment. (The rest of an aircraft is very soft, and would splatter like an egg.) However, merely cracking the containment would not inflict serious damage inside. To do that, either the engine must fall in (instead of being deflected), or enough jet fuel would have to spill in to burn in a serious fire. Even then, the heavy steel reactor pressure vessel would probably be undamaged, because it is surrounded and protected by thick concrete radiation shielding.

The only way that much radioactivity could be spread is if a steam explosion were to occur. The only conceivable causes could be either a runaway overpower or complete loss of cooling. We know of no credible way that the crashing airliner could cause an overpower. The worst that could be expected is what is known as a "blowdown," where a main cooling-water pipe is ruptured by the falling aircraft engine, and the pressurized water turns to steam. Under these circumstances, the chain reaction would simply shut down.

However, if the emergency core-cooling system was also disrupted, the ability to cool the core of the shut-down reactor could be lost. While a steam explosion in a current power reactor resulting from complete loss of cooling cannot be theoretically ruled out, it is no longer considered realistic by the Nuclear Regulatory Commission - even when evaluating "worst case" scenarios.

We can forget about steam explosions.

What could happen, if an engine fell in and all cooling were lost? Some of the fuel would probably melt. After a few hours it might work through the reactor vessel, spread out and solidify down below. Some fraction of the more volatile radioactive material might escape to the atmosphere. However, with a timely, temporary evacuation, in accordance with the site's emergency plan, no serious off-site exposure to radiation should occur.

There are two other potential targets at a typical reactor site: spent fuel in dry storage and in wet storage. The dry-storage casks are made of concrete or thick steel. If directly hit by a jetliner, a few of them might break, but the ensuing fire could not disperse a large amount of radioactivity. Nevertheless, temporary local evacuation might be called for.

The storage pools used for fresher spent fuel are somewhat more vulnerable, although they are not pushovers. Nonetheless, a jetliner considerably smaller than a 767 might be sufficient to disrupt one. This alone might make the pool a more attractive target than the reactor itself.

So nuclear plants are low-payoff targets.

There is a way to virtually eliminate the damage potential of the storage pools: the Yucca Mountain repository in New Mexico should promptly be opened as an interim storage facility, and the spent fuel currently in pools beside reactors should be moved to storage pools in this secure, underground location. Transportation in "wet" casks would be a very low-risk operation, although probably there are not now enough casks to allow a complete, expeditious transfer. Thus some hardening of the storage pools might be wise, and as much fuel as possible should be in the less-vulnerable dry-storage type of cask.

Yucca Mountain should be considered an interim storage facility because reprocessing spent reactor fuel should be reconsidered in light of new, proliferation-resistant technologies. Re-using spent fuel in fast reactors is very attractive - what otherwise would need to be stored for ten thousand years is now consumable fuel, and the residual waste is harmless in 500 years.

Given the instability near the Persian Gulf and the fragility of the Saudi monarchy, oil shipments could soon be disrupted. The less we depend on this oil the better. In the long run, fossil fuels are limited - nuclear power is not. We should not allow uncalled-for panic, politics, or political correctness to curtail the safe use of nuclear power.

Gerald Marsh is a physicist who served with the U.S. START delegation and was a consultant to the Office of the Chief of Naval Operations on strategic nuclear policy and technology for many years. George Stanford is a nuclear reactor physicist, now retired from Argonne National Laboratory after a career of experimental work pertaining to power-reactor safety. Courtesy of The National Center for Public Policy Research.

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