PRAGUE: Splitting the first atom was a scientific milestone in the 20th century, but a getting rid of the world’s highly radioactive waste is an achievement waiting for scientists to discover in the new millennium.

And according to one expert at a scientific conference on Thursday in Prague, researchers exploring the most feasible solution to nuclear waste disposal — deep underground burial - are struggling to overcome serious technical hurdles.

Despite years of study, scientists are still hunting for a safe burial method that can reliably prevent radiation from seeping into air and groundwater for centuries to come, said Spanish scientist Antonio Gens, a waste disposal expert who addressed the 13th annual European Conference on Soil Mechanics and Geotechnical Engineering.

Gens, a professor at Barcelona’s Technical University of Catalonia, talked about rocks and soil but steered clear of politics while addressing about 300 scientists from around the world.

He noted that underground burial of waste in cylinder casings is the favoured proposal for disposing the world’s 250,000 tons of highly radioactive waste, a dangerous stockpile that grows annually by about 10,000 tons.

No longer are scientists looking at sliding the waste under polar ice, burying it at sea, or shooting it into space, he said.

That means the geotechnical engineers who now build tunnels, landslide barriers and seawalls will have a lead role in caring for the waste which is mainly being stored temporarily at the world’s 441 nuclear reactors, Gens said.

Moreover, the size of the task will grow after power companies launch 32 reactors now under construction, including 10 in central and east Europe. Then the job will continue during waste-site monitoring periods that are likely to last hundreds of years.

But first, Gens said, researchers must find a burial system that works.

“The question is whether (the system) will be able to maintain its effectiveness over a long period of time,” he said. “Up to 1,000 years.”

For example none of the waste-disposal methods studied so far in Europe and North America have overcome the problem of fracturing, Gens said.

Fractures develop when underground rock is exposed to the kind of high heat that nuclear waste emits for hundreds of years. Such fractures raise the risk of radiation leaking into groundwater and air.

Researchers have conducted on-site, deep-shaft studies of potential burial methods in rock salt in Germany, granite in Sweden and Italy, and hard clay in Switzerland. None have involved radioactive waste but have looked at burial methods in vertical and horizontal shafts at least 200 metres underground.

In North America, researchers have studied burial systems at Yucca Mountain, Nevada, and the Whiteshell site in Manitoba.

Some scientists hypothesized that cracks in some kinds of fractured rock can be “self-healing”, or close by themselves, Gens said. —dpa