Disposing of nuclear waste by imitating nature. Australian scientists develop a compound that locks in radioactivity

Technicians duck under motionless blue robotic arms. High-speed drills scream. A silent, red, 250-ton hot press towers over the scene like an oversized Go-Bot toy. The machinery stops, and the final product sits on a steel conveyer: a hard, dense, black pancake of Synroc. Invented in 1978 by Ted Ringwood, a professor at Australian National University, Synroc is a man-made mineral compound designed to store radioactive waste.

In some scientific circles, Synroc is considered the most significant advance made recently in nuclear-waste disposal. And, as concern over the greenhouse effect sparks calls for a fresh look at nuclear power, Synroc, too, is garnering more attention.

``We're still in the test stages. This nonradioactive full-scale plant has only just become operational,'' says Jack Walker of the Australian Nuclear Science and Technology Organization, a government research agency.

Synroc's uniqueness lies in its ability to mimic mother nature. There are naturally occurring minerals in the Earth which have, for millions of years, retained radioactive atoms within their crystalline structure.

Similarly, a blend of Synroc minerals (titanium oxide, a common paint pigment, is the principal one) ``absorbs the various elements of the radioactive waste and locks them in tightly, locks them in almost atom for atom,'' says Mr. Walker.

But just as Synroc was being discovered, France was completing a borosilicate-glass waste plant. This Plexiglas-like substance is currently the only other viable method of immobilizing 20 to 30 tons of liquid nuclear waste worldwide. Liquid waste is a small percentage of all radioactive waste, but it is difficult to dispose.

Synroc is not yet available commercially. Under public pressure to safely dispose of high-level waste as quickly as possible, many governments have opted for glass. Plants are now being built in France, Britain, and the United States.

Still, Synroc is considered by some scientists to be a better long-term waste disposal form. It is tougher, more resistant to high temperatures and corrosion. And it holds more nuclear waste per volume.

Synroc project leader Dr. Keith Reeve believes he has a superior product but hesitates to criticize glass at the risk of increasing fears about nuclear waste. ``Glass is accepted as a first generation waste form because it's the only one ready,'' he says. ``We haven't pushed the point that glass has real problems because, if you treat it properly, it's OK.''

But ``OK'' may not satisfy everyone. Glass must be cooled in vaults for about 50 years before it can be buried. Synroc may be buried almost immediately. Glass requires a safer underground burial spot. In a worst-case scenario, if hot water under high pressure were to enter a storage area, glass could leach radioactive waste at a rate 1,000 times higher than Synroc.

Glass proponents argue that Synroc is still unproven. If buried in a geologically safe area, the risk of water seepage is minimal, and only under unlikely extreme temperatures does Synroc offer an advantage.

The main interest in Synroc is coming from energy-poor Europe and Japan, where used nuclear fuel rods are reprocessed to salvage remaining fuel for reactors. Synroc is especially suited to disposing of high-level liquid radioactive waste - a byproduct of reprocessing spent nuclear fuel.

The US defense industry has 70 million gallons of liquid radioactive waste in temporary storage. Plans are to put that waste in borosilicate glass. Most waste from commercial nuclear reactors remains in solid form, and the focus is on finding a safe place to bury it. US government funding for Synroc research has stopped. Geologist Rodney Ewing at the University of New Mexico believes this is a mistake.

``In the US, the [underground] repository is seen as the most important barrier to radioactive waste. I don't think that's the right way to look at it,'' Dr. Ewing says. ``If we can make a waste form that's relatively inert, we should use it. Then, you don't have to worry about where you bury it.''

Britain, Japan, and Italy are working with the Australians doing small lab tests on Synroc with waste from their nuclear plants. Although Australia is a major uranium exporter, it does not generate high-level radioactive waste because it has no nuclear plants.

The $10 million (Australian; US$8.2 million) in government funding for Synroc runs out by 1991. By then, researchers expect that production problems and scientific testing will be over. Dr. Reeve has been directed to seek commercial support for building a fully-operational Synroc plant.

At this point, one of the 26 nations with nuclear power, not Australia, will probably be first to use Synroc. The ruling Australian Labor Party has a policy which forbids the import of radioactive waste. But ALP is just now embarking on a broad review of its nuclear policy.

And a significant change may be in the wind. At the ALP National Conference in June, Sen. John Button, Minister of Industry, Technology, and Commerce, supported a policy review saying, ``We've been putting a lot of money into Synroc. ... We've got to ask ourselves what we're going to do with it.''