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Helping nuclear plants keep their cool

monitors November 6, 1996
Web posted at: 4:45 p.m. EST

From Correspondent Dick Wilson

WEST LAFAYETTE, Indiana (CNN) -- Sometimes a complicated problem can be solved with a simple solution, even when the problem is as difficult as keeping a nuclear reactor cool.

Traditional systems have relied on powered mechanical pumps. Now, a simpler method relies on the law of gravity.

Accidents at Three Mile Island in 1979 and Chernobyl in 1986 were pivotal events in the history of nuclear power plants.

Both became fixed in the public mind as fearful, even disastrous accidents. In both cases a cooling system failure caused the reactors to overheat.

Some nuclear scientists say there is a new and safer way to run nuclear power plants that could prevent such mishaps.


At Purdue University in Indiana, scientists are working on a reactor-like device that uses water circulated by gravity to keep the core cool. Most nuclear plants throughout the world currently rely on a system of electric pumps to keep from overheating.

Purdue scientists say their gravity-driven cooling system would keep working by itself, even if operators walked away during an accident.

The project is now in the design and testing phase.

In one test, scientists simulate the conditions of a main steam-line break. "That is one of the worst scenarios. If you break this large pipe, then the coolant will gush out," said Purdue scientist Mamoru Ishii.

The gravity-based system responded as it was designed to, circulating water and steam in a continuous loop to keep the scale-model reactor at a safe temperature automatically.

The prototype system is run by a set of computer codes, rather than plant personnel.

"The final result will be a ... next-generation computer code which the public can have confidence in," said professor Victor Ransom, who is also on the Purdue team.

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This type of passive safety system may sound simple. But scientists say it could take another 10 years of research and construction before the design is ready to be used in a nuclear power plant in the United States.


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