Digging deep

Geologist Ian Clark and his students have spent the past several years testing the geologic stability of a proposed nuclear waste disposal site near Kincardine, Ont. M.Sc. student Laurianne Bouchard extracts methane from rock samples to measure the isotope content.

 

“I am pro-nuclear. The facts show it to be safer than thermal or hydroelectric power, and it now seems we have long-term solutions for radioactive waste.”

– Ian Clark

Japan and Germany are scrapping nuclear energy. In Canada, Quebec’s Gentilly-2 nuclear plant is being decommissioned after 29 years of service. On the surface it seems as if nuclear power is being phased out in Canada and around the world, yet nothing could be further from the truth.

As energy demands intensify globally, the need for nuclear fuel runs deep in Canada and other nuclear-powered countries. But it raises two urgent questions: is nuclear really the best way to go, and just what can we do with the resulting radioactive waste?

“Nuclear energy is absolutely, 100 percent, the way to go,” says Ian Clark, a professor in the Department of Earth Sciences at the University of Ottawa and the director of the G.G. Hatch Stable Isotope Laboratory, one of Canada’s leading isotope analysis facilities. According to Clark, no matter what metric you use—energy yield per weight of fuel, ecological impact, or safety based on deaths per terawatt hour of energy production—nuclear power generation has the smallest environmental footprint and is the cleanest and safest form of energy, compared to coal, oil, biofuels and even solar and wind.

“That’s the good about using nuclear power for energy,” says Clark, who will be leading a cluster of state-of-the-art geoscience laboratories in the University’s Advanced Research Complex, slated to open in spring 2014. “The bad is that nuclear power production produces dangerous waste that remains radioactive for thousands to millions of years.”

With the continued use and expansion of nuclear power, the long-term management of nuclear waste has never been more pressing. Current options for disposing of nuclear waste all have major drawbacks: reprocessing spent fuel is very expensive, short-term above-ground storage is prone to leaks and ocean disposal is ecologically unsound and contravenes the United Nations Convention on the Law of the Sea. These obstacles are what have encouraged most countries to investigate deep geologic repositories (DGRs) for the long-term storage of nuclear waste.

“DGRs are vaults excavated deep within stable geologic environments that are typically about 750 metres deep,” explains Clark. “The trick is finding such environments, places that aren’t prone to water movement that can bring radioactive materials back to the surface.”

Clark and his students have spent the past several years testing how groundwater found in rock pores (porewaters) moves through the farfield—the ground layers between the planned vaults and the Earth’s surface—at the proposed Bruce DGR site for low and intermediate level waste near Kincardine, Ont. The team is part of an international research program managed by the Nuclear Waste Management Organization and Geofirma Engineering of Ottawa.

“We drilled down 860 metres,” explains Clark, “and pulled up rock core to see what the conditions are like to bury nuclear waste. Samples from over 4.45 kilometres of core came to the University of Ottawa for analysis. That’s impressive, but the real challenge was to get the water out of all that apparently dry rock for analysis.”

His team of students and laboratory technologists extracted the water and gases from these rocks using a technique they had to specially develop. It involves baking the rocks under a vacuum at 150°C and collecting the water in sealed tubes using liquid nitrogen. By measuring isotopes, dissolved salts and trapped gases in the water, they determined that the area proposed for the DGR site near Kincardine contains porewaters and gases that, incredibly, haven’t moved for some 400 million years.

“It eases concerns about storing nuclear waste in DGRs, at least at sites that are geologically similar to the planned Bruce DGR site,” says Clark. “It looks like this region is a place with predictable geology for tens of kilometres or more in all directions—perfect for a DGR of nuclear waste.”

“That’s one of the reasons why I am pro-nuclear,” he adds. “The facts show it to be safer than thermal or hydroelectric power, and it now seems we have long-term solutions for radioactive waste.”

 

by Sean Rushton

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