Wednesday, May 13, 2026
Nuclear power’s profile has surged in recent years as a possible source of green power.
But is nuclear sustainable when it requires massive amounts of water to function?
The province of Ontario is looking to build one of the biggest nuclear power stations in Canadian history near Port Hope, Ont., but one expert warns the province’s largest source of freshwater could be at risk.
Swim Drink Fish founder Mark Mattson has voiced concerns on his Substack about the long-term effects of nuclear mega-projects on the flora, fauna and overall water quality of the Great Lakes.
Mattson said he has been involved in energy issues since the early 1990s as one of the counsels for the Nuclear Liability Act’s constitutional changes and counsel for the Ontario Energy Board during Ontario Hydro reviews. He also served as executive director of the Environmental Bureau of Investigation in the 1990s, a non-profit established to investigate pollution and enforce environmental laws.
“It seemed after the last big push in the early 1990s where Ontario said they needed to double their nuclear capacity by 2020 with a 25-year plan or we’d be freezing in the dark, that hearing went two and a half years and at the end of it, we didn’t get a decision,” Mattson said.
The numbers and evidence surrounding nuclear power had changed during the hearing to such an extent that the Ontario government withdrew the proposal “and nothing’s been built since,” he said.
Recent announcements by the Ontario government about extending the life of existing nuclear facilities, building small reactors and new larger facility have created a new wave of enthusiasm for nuclear power, Mattson said, but there are issues to consider regarding water quality, especially regarding the Great Lakes.
But while nuclear power is touted as a way to reduce greenhouse gas emissions, he said, many of the components of a plant either produce emissions or require environmentally harmful chemicals to operate.
“These are huge turbines that need all kinds of lubrication, backup power and diesel engines. They’re huge operations and it’s not just splitting the atom,” he said.
Mattson added while American reactors have largely moved on from older, less efficient cooling technologies, Canada still uses a system that consumes an enormous amount of freshwater.
“We’re concerned about the Canadian technology (being used) because it takes for granted the quantity and quality of water that they’ll have access to from Lake Ontario and Lake Huron,” Mattson said.
The Canadian systems use a process called ‘once-through cooling’ which is illegal in the United States, he said. Instead, US plants use cooling towers and closed-cycle cooling where the same water is recycled to cool reactors rather than drawing on an outside source.
“Once through means you’re just sucking constantly from the lake and spitting it out and the amounts of water are huge” Mattson said. “When you’re bringing it in from the lake, you’re sucking in fish, eggs, embryos and trapping them in screens and then the water goes back out at really high temperatures, up to 40 degrees Celsius.”
Mattson concluded that while the earlier nuclear plants may not have known of the effects on the water and organisms within them, they are currently aware and at this point facilities should not be built on the Great Lakes.
In a reply to questions about environmental review processes from Water Canada, Canadian Nuclear Safety Commission (CNSC) media relations spokesperson Michael Gosselin said the CNSC conducts environmental protection reviews (EPRs) for all nuclear facilities with potential interactions with the environment, in accordance with its mandate under the NSCA to ensure the protection of the environment and the health and safety of all people in Canada.
“These science-based technical reviews among many other areas track waterborne effluent, assess the local aquatic environment, and water quality,” he said.
He added reviews are based on information that the proponent or licensee submits to CNSC, such as licence applications and supporting documentation that outline environmental protection measures and programs, compliance and technical assessment activities completed by CNSC staff, such as reviews of environmental monitoring data and environmental risk assessments.
The CNSC also has an independent environmental monitoring program which samples air, water, food, and soil near nuclear facilities, relevant regional health studies, other governmental monitoring programs and Indigenous knowledge studies, Gosselin noted.
“For thermal effects on water, licensees or project proponents must show that their activities do not pose an unacceptable risk to aquatic life. They usually do this by using temperature loggers and computer models to show how far and for how long warmer water spreads. They also use nearshore habitat surveys and scientific studies to identify sensitive species, life stages, and temperature limits that could cause harm,” he said.
The long-term costs of running nuclear power plants are also a focus of concern for Mattson, who cautioned that once built, a plant must be used until it reaches its end point.
“When you have nuclear power plants, they’re baseload (24/7 high-capacity operation) and you need to pay them off over the next 25 years. You can’t turn them on or off or in six years and decide to use something else, it’s going to take up the 25 years, and they have to use up their baseload,” Mattson said.
“Building these reactors on drinking water, you really need to have stricter health guidelines and certainly that’s not the case in Canada. We allow some of the highest levels of tritium into our drinking water at 7,000 Bq/L. In the U.S. it’s 70-700 depending on the state,” he said.
“I don’t want to be seen as being certain these are having terrible impacts, but I am saying that these need to be scrutinized, shared and looked at publicly,” he added.
Gosselin pointed to the CNSC’s review process as a suitable form of analysis for nuclear technologies of both large and small scale.
“The CNSC has a robust regulatory framework that builds on experience from regulating existing designs and remains suitable for licensing activities associated with varying facilities and technologies. The regulatory framework is flexible, and its requirements are technology-neutral and performance-based. Therefore, it can assess a broad diversity of operating and safety technologies, regardless of the scale and capacity of a given project,” he said. “Integrated Impact Assessments between IAAC and CNSC are purpose-built for such projects.”
Warren Frey is the Associate Editor of Water Canada.
