Man-made vault for OPG’s low-level nuclear waste

22 December 2011

Ontario Power Generation (OPG), the public utility that owns the Darlington, Pickering and Bruce nuclear operations, is seeking federal permission to construct a vault 680 metres below the Bruce complex, near the eastern shore of Lake Huron, for the storage of nuclear waste.

The site would be a man-made rock cavern carved out of tectonically stable shale and limestone, a kilometre from the lake. But unlike the planned national deep geological repository for intensely radioactive spent reactor fuel, the “deep rock vault” in Tiverton, Ontario will handle only low and medium radioactive waste. High-level nuclear waste is forbidden.

About 200 000 cubic metres of radwaste — about a century’s worth — from the Darlington, Pickering and Bruceplants is to go into in the vault.  OPG says the 450 million-year-old rock formations will remain stable for at least the next few million years and, “limit the movement of radioactivity to very slow rates.”

Nearby Goderich hosts the world’s largest underground salt mine, evidence the area has not been subjected to deep groundwater activity for a very long time. Under pressure, such as that from an earthquake, salt formations tend to flow and become self-sealing at depths of about 600 metres. 

Albert Sweetnam, OPG’s executive vice-president of nuclear projects, defended the project against worries that it is too close to Lake Huron. At 680 metres it is, “completely isolated from the deepest point of the lake in the vicinity, about 180 metres,” he said. The presence of salt formations and absence of deep groundwater means that "the only way to extract that water out of that rock is to crush it. The rock is impermeable. The water doesn’t move" he said.

Similar low and intermediate nuclear waste repositories already operate in Sweden, Finland and the United States. OPG says it is too early to calculate the total cost, though it will certainly amount to hundreds of millions of dollars. Until then, much of the waste will continue to be stored at Bruce’s 40-year-old, above-ground Western Waste Management Facility.

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