Concerns Linger Over Canadian HEU Waste

The International Atomic Energy Agency and Canadian government have reacted to potential risks posed by a massive cache of highly enriched uranium waste at a medical isotope production site near Ottawa, the Ottawa Citizen reported on Tuesday (see GSN, Jan. 25).

The 6,340-gallon Fissile Solution Storage Tank at Canada's Chalk River site is calculated to hold liquid with roughly 386 pounds of 93 percent-enriched uranium, as well as materials including plutonium, tritium and mercury. The highly acidic refuse -- generated over 17 years during the production of the medical isotope molybdenum 99 -- is thought to nearly fill the dual-layered steel container, which was retired eight years ago from further use.

Between 44 and 99 pounds of highly enriched uranium could fuel a weapon similar in size to the bomb dropped during World War II on Hiroshima, Japan, according to the Citizen. In a 2009 assessment of weapon-related risks involved in manufacturing medical isotopes with highly enriched uranium, a U.S. National Research Council panel said material in the Chalk River site container was "of particular concern."

The vessel was equipped in June with advanced sensory equipment enabling the International Atomic Energy Agency to track the waste levels from the U.N. organization's headquarters in Vienna, Austria. Two minor releases of material took place in 2006 and another incident was reported in 2009, though the underground container's physical status has been described as excellent.

The Canadian Nuclear Safety Commission, though, warned in June that site operator Atomic Energy of Canada must contend with "challenges" posed by  "the degradation of some (FISST) support and monitoring system components."

Any fissile activity inside the container could break open its lining and allow toxic contents into the surrounding area, though no detonation could result from such an event.
"Because Canada's facility for this liquid waste is full, its operators have conducted criticality [fission reaction] studies to ensure that storage could be reconfigured to accommodate additional material or that some waste could be removed and immobilized in concrete to reduce overfill," Cristina Hansell, an expert with the James martin Center for Nonproliferation Studies in the United States, wrote in Nonproliferation Review. "Of course, the immobilized material will eventually have to be removed from the concrete in order to downblend it for long-term storage, not a simple process."

"Though it is not extremely likely that a terrorist will steal material in Chalk River, Canada, and create a nuclear device that is detonated in a North American city, it is not impossible," Hansell stated. "If nuclear terrorism is to be prevented, then Mo-99 production should be recognized as an increasingly weak link" (Ian MacLeod, Ottawa Citizen, Dec. 20).
December 20, 2011