Reactor Design Aims for Safety

NUCLEAR power, says Lawrence M. Lidsky, can be ``the safest, least environmentally damaging source of large-scale central power available to mankind.'' And the United States, adds the Massachusetts Institute of Technology (MIT) professor of nuclear engineering, can lead the way with a strikingly different nuclear technology than is now in use - first for itself, then for export to other nations.

Dr. Lidsky leads a team that has designed a gas-cooled, modular nuclear reactor (see diagram). Part of Lidsky's design would utilize some basic technology that has been known for decades, but was ignored in the 1950s when nuclear first went commercial - largely because the US Navy had advanced the use of light water reactors (LWRs). Comparing the LWR with the modular reactor, Lidsky says, ``We took one that was cheap and tried to make it safe. Now let's take one that is safe and make it cheap.''

He unhesitatingly opposes redesign of LWRs already in use across the US - something the nuclear industry is doing as rapidly as possible. (See related story on Page 9.)

``Inherent safety'' is the key phrase that drops from this scientist's lips. Lidsky says his team's modular reactor just won't melt down, even in a worst-case scenario. A test reactor of the type he backs successfully operated in Juelich, West Germany, from 1967 until this year. Three full-scale loss-of-coolant tests were performed in the summer and fall of 1988. The results were filmed, and the Public Broadcasting System will show some of this film next year. It was loss of coolant that led to the Three Mile Island reactor accident in Pennsylvania. According to Lidsky, the technology he and his team propose includes the following advantages over LWRs:

The fuel can't melt (releasing radioactive waste) even if the cooling system fails. There could be no meltdown. Each particle of fuel is encased in a tiny spherical shell of silicon carbide that is immensely strong and heat resistant.

The reactor utilizes gas (helium) for cooling, which also would be used to drive turbines, eliminating the need for making steam - which is highly corrosive.

The reactor is smaller and therefore its heat can be more readily removed.

The inherent safety of the reactor can be tested at the manufacturing facilities where the reactors are built before they are taken to a plant site.

Such prototype testing simplifies the licensing process greatly and can make reactors uniform throughout the US.

A power plant based on these reactors could utilize a number of them in a group, providing whatever megawattage is required. Or, because of their inherent safety, plants could be spread out more than they are now, serving any number of rural areas, for example, or be utilized for other needs.

The Japanese, highly successful with their LWRs, know about Lidsky's work. Tokyo Electric Power, for example, and the Toshiba Corporation support his project financially. Other Japanese organizations have sent people over to work in his lab at MIT. The United States Department of Energy also chips in.

Lidsky says, ``If the US does not build this plant, the Japanese will take it from us; they are not participating in this just for charity.''

The most powerful opponent of his plan, Lidsky says, is the US nuclear industry itself. Top industry spokesmen deny they really oppose his plan. Karl Stahlkopf, director of materials and systems for the Electric Power Research Institute (EPRI), says the Lidsky concept is a ``viable candidate, but not for this century, since more development is needed.'' EPRI represents the research goals of the existing nuclear power industry. On timing, Lidsky says: ``You know, there are only 10 years left in this century anyway. Why not get the package going?''

John Deutch, provost of MIT and a member of Jimmy Carter's Presidential Commission on Reactor Safety, which was appointed after the Three Mile Island accident, says he backs the Lidsky design. But Dr. Deutch also says many nuclear safety concerns must be considered and that just ``one technical fix alone isn't enough.'' He says present safety problems in the nuclear power industry ``are not fatal'' and need to be addressed. Most important, he says, is to ``insure technical competence within the utilities.''

This term, ``technical competence,'' raises a point Lidsky himself highlights in explaining the weaknesses of LWRs. He says the key problem with present LWRs, for the US in particular, is that their cooling needs demand too much complexity and reliability in both technology and operation.

In Lidsky's words, ``sloppy, decentralized, contentious, free-spirited America can't consistently build and run them to the public's satisfaction.''

Lidsky says that the design he backs is not only safe, but also benign toward nature. Coal- and natural-gas-fired power plants, he says, add to the greenhouse effect. Gas does not cause acid rain (unless there is sulphur in the gas), but most coal-burning plants do. And acid rain is presently the biggest known spoiler of the environment.

Modular nuclear technology, Lidsky claims, will eventually appeal to power companies on the basis of technology, the environment, investment, safety, and cost. Environmentalists, he says, will see that a truly safe nuclear technology is an answer to both acid rain and the greenhouse effect. The public will accept the new technology, he says, when the power industry and environmentalists come to terms with an authentic second generation of nuclear power plants.

He concludes: ``Most important is the fact that the new reactors can be subject to full-scale, worst-case tests. This is what the public deserves, and nothing less.''