Nuclear Enters a New Era

`URGENTLY wanted: a clean, safe, abundant, inexpensive, and inexhaustible energy source. Respond c/o Planet Earth. Collect calls OK.'' Such an advertisement might be prompted by any of several concerns, from the greenhouse effect to Persian Gulf volatility to trade imbalances. But so far the combination of specifics disqualifies every candidate: coal, crude oil, natural gas, solar, hydropower, geothermal, wind, and wood. Nuclear is certainly no option - or is it?

That depends on whom you ask. Proponents of nuclear energy say it already is an option; detractors say it never can be for reasons of cost, operational safety, and dangerous waste output.

Now a third opinion is being voiced. Scientists at the Argonne National Laboratory, a United States Department of Energy research facility in Argonne, Ill., agree with nuclear's opponents that current technology and even next-generation technology isn't worth the trouble. They say a massive switch from fossil fuels to nuclear would exhaust uranium reserves in decades, while leaving behind waste that would be dangerous for thousands of years.

``It is not sufficient to build prototypes of new reactors that cannot ever have the properties required,'' says Charles Till, associate laboratory director for engineering research at Argonne. ``A lot of money can be spent and a lot of commitment squandered, without touching what is really necessary to realize the long-term benefits of nuclear power.''

Argonne has been working on nuclear technology of its own. Dr. Till and others say they are on the verge of demonstrating that Argonne's technology would turn the usual nuclear equation around: Waste would be dangerous for only a few hundred years, while power output could last for thousands of years.

The world's 424 currently operating nuclear plants have an average capacity of 765 megawatts, totaling 17 percent of all electricity, according to the International Atomic Energy Agency in Vienna. Officials there say it would take 1,500 nuclear plants of 1,000 megawatts each to produce half the energy the world consumes.

If they were light-water reactors, like all 112 nuclear plants now operating in the United States, they would not only exhaust the world's known uranium reserves in 20 to 30 years, but they'd turn the uranium into nuclear waste requiring storage.

Most of the world's nuclear reactors are based on US light-water-reactor technology, according to Steve Unglesbee, manager of media relations for the United States Council for Energy Awareness. The Washington-based council is an organ of the commercial US nuclear industry that touts nuclear as a reliable domestic source of energy. Other countries do employ other types of nuclear technology, he says. One is the breeder reactor, which makes far more efficient use of uranium, but still creates long-lived w aste.

Unglesbee does not see waste storage as a problem: ``Waste, in the form of spent nuclear fuel, has been stored safely at the nation's nuclear-plant sites for more than 30 years, with no incident that would compromise public health or safety,'' he says.

But breeders are also controversial because during the reprocessing of waste into new fuel, bomb-grade plutonium is isolated.

The Clinch River Breeder Reactor at Oak Ridge, Tenn., was the largest breeder attempted in the United States. Worries that it would be uneconomical and would lead to nuclear-weapons proliferation led Congress to halt construction in 1983, leaving a $1.7 billion hole in the ground.

As for future technology, in the US, Westinghouse, General Electric, and ABB-Combustion Engineering are designing reactors with built-in features that ensure safety of operation, Unglesbee says.

Either way, these reactors won't reduce the amount of waste or increase the efficiency of fuel use.

But new breeder technology that promises to solve these problems is on the horizon. The Integral Fast Reactor (IFR), under development at the Argonne National Laboratory, is the only advanced-reactor research and development program in the United States.

Building 1,500 IFRs, Argonne scientists say, would stretch the life of known uranium reserves to 2,000 years and reduce the danger time from the waste to 200. What's more, IFRs could perform the same trick with all the waste from existing nuclear plants.

So far, Congress has ensured that IFR development receives adequate funding, says Till, who heads the IFR project.

Meanwhile, the nation's utilities are starting to take note. Technical delegations from Commonwealth Edison in Illinois and Duke Power in Florida, two of the top nuclear-power utilities in the country, will visit the Argonne project this spring.

``Five years ago you couldn't expect them to be much interested. It was just an idea in a few of our heads,'' says Till. ``But now it's real.''

The IFR's design, fuel type, and fuel-reprocessing technique represent revolutionary improvements over existing technology, Till says. And an IFR plant should be no more expensive to build than the best-managed of previous nuclear projects, which can produce power for far lower costs than coal-, oil-, or gas-fired plants, he says.

To explain how the IFR would solve these problems, Till starts with the reactor core. Thorough, efficient fission and breeding are functions of the speed of neutrons departing split atoms. The water that cools light-water reactors slows down neutrons, he says. And the ceramic fuel rods in both light-water reactors and breeders slows the neutrons further.

The IFR, like other breeders, is cooled by sodium, a liquid metal that pours like water. Sodium inhibits neutrons very little. And unique to the IFR, its fuel is metal, again much more transparent to neutron travel. All-metal fuel had been tried before but couldn't be made to last long in a reactor until Argonne found a way, Till says.

Next comes reprocessing. For the breeder programs in other countries, this is a very costly, complex process that is performed at giant facilities serving many reactors. It involves segregating plutonium from other material, which might tempt governments or light-fingered terrorists to make a nuclear bomb. Also, the process fails to achieve perfect separation of short-lived waste from radioactive chemical elements called actinides (see related story), so these countries still must grapple with a million -year hazard.

The IFR uses a radical, new electrochemical reprocessing technique. The metal fuel rods are immersed in a liquid salt bath. When an electric current is passed through, the rods dissolve and all the U-238, plutonium, and other actinides go in one direction, the short-lived waste in another.

At no stage can this process isolate weapons-grade materials. And none of the fissionable but dangerously radioactive actinides are thrown away. The reusable materials are injection-cast back into new fuel rods and returned to the reactor.

This process is so simple and cheap, Till says, that each IFR plant could do its own reprocessing. ``It's a nice process if we can make it work'' in plant scale-tests scheduled next year at Argonne's reactor in Idaho, Till says. So far the IFR reprocessing has been performed successfully on 20 pounds of material at a time.

As for operational safety, the IFR takes advantage of natural properties to make the reactor passively safe - that is, needing no human or mechanical intervention in a crisis.

If the all-metal fuel gets too hot, it expands, stopping the reaction. ``The power drops like a rock,'' Till says. Also, the internal structure of the vessel is designed so that natural circulation of the sodium coolant through the core begins anytime that forced pumping stops.

In 1986, full-power tests at the Idaho reactor simulated the conditions at Three Mile Island in Middletown, Pa., and Chernobyl in the Soviet Union. The reactor shut itself down, and the fuel and coolant remained within safe temperature limits.