Burying nuclear waste

by Tyler Shendruk
Published: Apr 4

The problem

A FIFTH OF the world’s uranium comes from Canada. CANada Deuterium Uranium (CANDU) reactors have been safely running since the 1950s, but nuclear energy is not without its problems. A handful of leaks have occurred, raising questions about waste management.
Storage of nuclear waste is a particularly important question right now as there is a proposal to build up to four new nuclear reactors at the Darlington Nuclear Generating Station on the northwest shore of Lake Ontario.
Plans to ship waste to depositories in the shield are controversial amongst northern communities and many critics are uncomfortable with the idea of transporting nuclear waste over such long distances.

The researcher

Ian Clark is a professor in the Department of Earth Sciences at the U of O who uses the environmental isotopes found in nature to investigate deep crustal water and geochemical and biochemical processes that occurred millions of years ago.
Clark drills for rock samples and then analyzes the water and gases that have been trapped in these rocks for millions of years. He can determine if the groundwater has been totally isolated or if, over millions of years, new water has been slowly moving through the rocks.

The project

Clark uses natural isotopes as a tool but that knowledge is also extremely useful for predicting the outcome of burying nuclear waste. He was asked to be part of a team that would assess a site at Kincardine in southern Ontario, close to both the Darlington and the Bruce Nuclear generating stations.

The key

The Northern Shield may sound like the perfect place to bury nuclear waste, but according to Clark, it’s not. Yes, the igneous rock making up the shield is hard so nuclear waste shouldn’t diffuse through it, but it has fractures. The shield is leaky because faults let water flow quickly from one point to another.
Kincardine is much better according to Clark. He analyzed rock samples from six holes drilled 850 metres down to sedimentary rock—formed from deposited sand and clay at the bottom of ancient oceans—at the Kincardine site. Clark ground up these rocks and baked fistfuls to get about two drops of water, water that had been trapped for some 400 million years. Helium was also trapped in the rocks for more than 260 million years.
As these rocks are very tight and don’t fracture, and the site is very close to Ontario’s fleet of nuclear reactors, Clark believes Kincardine is an ideal environment and much better than any in the shield to bury nuclear waste.