Almost two years following an unusual fish occurrence at Canada’s largest nuclear facility that posed a safety challenge to its reactors, recently acquired documents shed light on the extraordinary nature of the incident. Experts caution that uncommon ecological circumstances are increasingly posing challenges for nuclear plants globally.
In February 2025, an overwhelming number of gizzard shad fish disrupted the cooling systems at Bruce Nuclear Generating Station near Tiverton, Ont., resulting in the shutdown of one reactor, decreased power in another, and a shoreline littered with dead fish along Lake Huron for several days.
CBC News obtained over 1,200 pages of federal and provincial records exposing how an environmental phenomenon involving a vulnerable fish species tested the capabilities of Canada’s largest nuclear power plant in unforeseen ways.
Bruce Power, the private entity managing the plant, declined a televised interview and later issued a written statement without addressing specific queries from CBC News.
Bruce Power’s internal investigation determined that the plant faced “a novel environmental event,” while Canada’s nuclear regulator described an unexpected influx of gizzard shad fish overwhelming the plant’s fish protection systems.
The aftermath of the fish incident prompted discussions on reactor safety within the industry, with experts emphasizing the critical need for maintaining multiple defense layers at nuclear facilities. Reactors at Bruce Power responded as intended when their cooling systems were disrupted, according to Douglas Boreham, a former manager at the plant.
A report by the Canadian Nuclear Safety Commission revealed the potential repercussions of the fish die-off incident, which disrupted cooling systems serving two operational reactors, resulting in the shutdown of Unit 2 and reduced power at Unit 1.
The unprecedented scale of the fish event, with millions of gizzard shad congregating near the plant, had significant environmental and operational implications. The incident raised concerns about the impact of changing ecological conditions on nuclear plant operations worldwide.
The incident at Bruce Power underscores the need for continuous adaptation and proactive measures to mitigate environmental disruptions that could impact nuclear plant safety. The industry faces increasing challenges from changing environmental conditions, necessitating enhanced monitoring and response strategies to safeguard plant operations in the future.