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Low Probability, High Impact: Radionuclides, Nuclear Waste and the Great Lakes

kevin bunch
Kevin Bunch
Pickering nuclear generating facility on shores of Lake Ontario

The IJC has heard from numerous people that radionuclides – essentially radioactive forms of elements often as small as atoms - should be considered for a future round of Chemicals of Mutual Concern by Canada and the United States. The comments were made at public hearings at the Great Lakes Forum in October and at public meetings around the Great Lakes in March.


So how threatening are these tiny radioactive materials? It’s complicated.

Tritium: the most numerous radionuclide in the Great Lakes

Radionuclides already exist in the Great Lakes, as a result of natural background radiation and at detectable levels resulting from fallout from global atmospheric nuclear bomb tests in the 1950s, according to Michael Rinker, who serves as the director general of the Canadian Nuclear Safety Commission’s (CNSC) directorate of environmental and radiation protection and assessment. Of these radionuclides, tritium is of particular interest because sources of tritium to the Great Lakes include natural tritium formation in the atmosphere, weapons testing fallout and operating nuclear power plants. The atomic test bombs produced tritium, a radioactive form of hydrogen that tends to bond with oxygen to become water; with the Great Lakes being as big as they are, tritium atoms found their way into the lakes originating from atmospheric fallout.

Tritium concentrations have been declining for decades, as tritium has a half-life of about 12 years, Rinker said. A half-life is the amount of time it takes for half of the element level or concentration to decay. Rinker said over the past half-century, tritium in the Great Lakes has likely been reduced to an average of around 6 percent of 1963 levels, the year when concentrations were at their highest, and when the Limited Test Ban Treaty was signed.

The exception is Lake Ontario, where concentrations are closer to 10 percent compared to 1963 levels due to the Pickering and Darlington power plants. These plants use a different, “heavy water” type of reactor than US plants on the Great Lakes. From 1980-1993, these heavy water reactors released more tritium into the water than boiling or pressurized water reactors used in US Great Lakes plants, according to an IJC report. The Darlington site now has facilities to treat tritium-concentrated water, and plants use containment and recovery methods to reduce the amount that escapes.

A map listing all the nuclear power plants and associated facilities around the Great Lakes
A map listing all the nuclear power plants and associated facilities around the Great Lakes. Credit: Watershed Sentinel

Even at its peak in the ’60s, tritium concentrations were well below the drinking water standards adopted by the World Health Organization (WHO) and Canada of 7,000 becquerels (Bq) per liter, a measurement unit for radioactive decay. The United States has a standard of 20,000 picocuries (pCi) per liter, a term used by scientists to measure how much radiation – and tritium – is in the water; one Bq is equal to 27 pCi. In Canadian communities located near nuclear power plants by the Great Lakes, tritium levels are between 6-18 Bq per liter – owing to those Canadian heavy water power plants – and the lakes overall have tritiuim levels beween 3-5 Bq per liter.

Existing nuclear power plants appear to be the greater concern for people living along the Great Lakes, with fears of spills, meltdowns or nuclear waste polluting the waterways and undermining the water supply. Radionuclides in the water, including tritium, aren’t easily removed from the water, according to the US Nuclear Regulatory Commission (NRC). Rinker added that historically there haven’t been major issues with radionuclides in the Great Lakes coming from power plants, which he attributes it to strict regulations and monitoring of nuclear plants in both countries.

John Keeley, spokesman for the US-based Nuclear Energy Institute, said the NRC and US Environmental Protection Agency (EPA) set strict limits in the amount of radioactive materials nuclear plants can release, based on the maximum possible exposure for members of the public. Typically, Keeley said, reactors release only a small fraction of that – less than one-tenth of 1 percent of the overall release limit. No reactor has ever approached EPA’s drinking water limit for tritium, Keeley added.

Rinker said that in addition to meeting regulatory limits, Canada and the United States require nuclear plant operators to improve their radiation protection measures as much as is reasonably achievable, to head off leakage and other safety issues before they can happen. For example, if a safe limit of a radioactive substance is 1,000 parts per billion (ppb) and plants are at 10 ppb, regulators would still like to see them achieve 8 or 9 ppb. Regulatory agencies also require oversight for nearly all changes at the plants – if a valve is being replaced, for example, Rinker said the process goes through a risk assessment to make sure everything that could go wrong is accounted for and prevented.

US nuclear plants also have followed voluntary groundwater protection programs since 2006 to improve the management of situations where radionuclides could get released, Keeley said. They have committed to reporting any unintended releases to local, state and federal authorities, even those below the required reporting threshold set by the NRC. Operators are required to monitor the environment around nuclear plants for radioactivity, including water supplies, shoreline sediments and food sources. These environmental reports are available on the NRC website. According to NRC staff, the reports show a few samples collected at the discharge points of power plants had very low levels of tritium, within regulatory limits. Concentrations of non-tritium radionuclides are generally non-detectable, and the quantity of radioactive materials released has been declining over time.

Both the CNSC and the NRC are regularly in contact to exchange technical information, cooperate and coordinate ­in nuclear safety matters.

“The thing about nuclear (power) is that you have to regulate very closely (to ensure there are no accidents),” Rinker said. “When everything goes fine, they’re a very clean industry. It’s just when there’s an accident that problems arise.”

A US Nuclear Regulatory Commission inspector checks out the Fermi II nuclear plant in Newport, Michigan
A US Nuclear Regulatory Commission inspector checks out the Fermi II nuclear plant in Newport, Michigan. Credit: Nuclear Regulatory Commission

The Deep Geologic Repository concerns residents too

Another issue that has drawn attention at IJC public meetings over the past year is Ontario Power Generation’s (OPG) proposed Deep Geologic Repository (DGR) by the Bruce nuclear power facility in Kincardine, Ontario.

Currently the waste is stored on the surface in warehouses, where it poses a greater threat to contaminate the lake, according to Frank Greening, who worked as a radiochemist scientist for OPG from 1978 through 2000 before retiring . That surface storage was always meant to be a temporary solution to dealing with waste from Bruce, Pickering and Darlington, Greening said, and as such they are poorly sealed and tend to leak tritium water vapor into the atmosphere and lake. Surface storage also poses a risk in case a weather event, such as a tornado, destroys the warehouses and spreads the waste around the region. Greening opposes the DGR site.

OPG hopes to seal away low-to-mid level waste materials for thousands of years about 1 kilometer inland of Lake Huron and 680 meters (2,230 feet) deep within the DGR – further down from the Lake Huron shelf – pending federal approval by Environment and Climate Change Canada. Minister of Environment and Climate Change Catherine McKenna recently provided a list of questions she wanted answered before issuing a decision; OPG responded May 26. The IJC hasn’t received a reference from the governments to research the issue, nor does it have any jurisdiction - the issue is entirely before McKenna.

The binational organization SOS Great Lakes and the Canada-based Stop the Great Lakes Nuclear Dump lists their concerns as: inadequate identification and review of alternate siting options; the proximity of the proposed DGR to Lake Huron; and the failure rate of other DGRs in Germany (using salt mines that  are in danger of losing stability) and in New Mexico (using granite, but seeing waste leak due to improperly sealed containers). The proposed DGR would be in limestone, but the group still doubts that it can be guaranteed to stay sealed for the 100,000-year radioactive life of some of these materials without radionuclides contaminating the water. They also estimate a leak could impact 40 million people in Canada and the United States, which has prompted opposition from local communities and politicians.

Greening said that while underground storage makes more sense than leaving it on the surface, the proposed site isn’t ideal. He said in the 1980s OPG hoped to bury it in the granite Canadian Shield – a rock known for being practically impermeable to water, economically unimportant and geologically stable on top of being a sparsely populated region – but was blocked when people in northern Ontario opposed it, and Manitoba passed a resolution preventing nuclear waste from Ontario being disposed of in the province. Rather than find another site on the Shield, Greening said, OPG wants to take it underground near where it already is.

“(The surface site) was never intended as a permanent storage site,” Greening said. “They’re taking the easy route of building a shaft (at the Bruce site) rather than move the stuff (to the Canadian Shield), which would cost a lot of money.”

Beverly Fernandez, spokeswoman for Stop the Great Lakes Nuclear Dump, said radionuclides entering Lake Huron from a repository 1 kilometer away at some point in their 100,000-year radioactive life is a concern that OPG has done little to mitigate. Fernandez fears this could set a precedent for disposing of nuclear waste at other Canadian and US plants in the Great Lakes basin. Additionally, scientific and environmental assessments for the other DGRs in New Mexico and Germany determined they were safe. But those DGRS have seen problems, casting doubt in her mind that the assessments for the Bruce DGR could be too optimistic.

OPG views the site as ideal, as it is not only far enough away from Lake Huron at the surface to be isolated from the water, but the depth and limestone rock formation around the site should keep radioactivity from leaking out and groundwater linked to Lake Huron from leaking in. Geologists have noted the rock layer has survived geological upheavels in the region over millions of years, and should remain stable for millions of years more.

The Canadian Nuclear Safety Commission (CNSC) and Environment and Climate Change Canada established a Joint Review Panel in 2012 to review the project under the Canadian Environmental Assessment Act and Nuclear Safety and Control Act. After public hearings and its own studies, the panel concluded that the DGR was the best solution for low-to-intermediate level waste, most of which would be safe after a century. It also found it was unlikely to impact water quality or ecosystems as long as mitigation measures are followed, such as spill response plans, monitoring, and stormwater protections.

Greening said an inventory report submitted to the Joint Review Panel by OPG underestimated the radioactivity  of waste to be stored on the site, relying on calculations rather than hard numbers that he had measured during his time there. While reviewers agreed with his assessment following an investigation, they opted to move ahead after concluding the risk of exposure for the public was still within safety margins. While he agreed, he said he remained concerned that they made a mistake and decided it wasn’t important.

OPG has countered that the report was only supposed to be an estimate and that it has continually worked toward improving that projection.

Lessons have been learned since those earlier German and US DGRs were constructed, Rinker said, based on the CNSC’s review of the proposal. And salt mines have fallen out of favor as good sites due to corrosion and geologic instability. The limestone at the proposed site hasn’t interacted with the surface or water table in more than 100 million years, and still contains residual seawater from when the continent was under the ocean that hasn’t seeped into Lake Huron or the fresh groundwater. The concrete shaft that would plug the DGR is a possible failure point, but it’s more likely carbon dioxide would escape than radionuclides, he said.

Greening said it doesn’t make sense to have waste near freshwater sources at all, since there is always some risk of contamination and there’s no need for water as coolant as there is with nuclear plants. And while OPG says they can safely drill to that depth without water filling the cracks and getting all the way down to the limestone, Greening argues the site still seems far less suited than one further from the lake simply by virtue of its geography.

Transporting nuclear waste

At the IJC’s March 28 public meeting in Buffalo, New York, several people expressed concerns about nuclear waste being transported across the Great Lakes from Ontario to a facility in South Carolina, either by truck across the Peace Bridge or by ship. Those folks, representing themselves or organizations like Sierra Club, were worried that the waste could get spilled into the environment, or be spread by an act of terrorism.

The US Department of Transportation (DOT) and NRC regulate the transit of nuclear waste in the United States and maintain that there have been no serious issues. Containers with low-level radioactive materials inside must be tested to simulate normal and rough transportation conditions, while those transporting more radioactive materials must be tested for accident conditions. Vehicles also need to stick to specified routes that minimize radiological risks, bypassing cities whenever possible, and take precautions to minimize the risk of terrorist attacks.

In the 20-year period from 1971 to 1991, 53 accidents were reported involving transportation of low-level waste, and only in four such events did the containers break and leak radiation outside of the vehicle – though they were quickly cleaned up with no noticeable increase in radiation levels, according to a state of Nevada study. For context, the US Department of Energy estimates that there are 3 million packages of radioactive materials shipped each year. The US DOT estimates that trucks move 84 percent of radioactive materials per year.

Greening said that in 2011, OPG had proposed shipping 16 radioactive steam generator tubes to Sweden for recycling and processing, but that plan was stymied based on public opposition. He said despite the CNSC licensing the proposal, fears of nuclear waste contaminating the water were strong. In the event that a tube sealed in a cask had rolled overboard, Greening added, that it was sealed and welded shut meant the risk to the public was very low, but nevertheless that risk was still too great for opponents.

Canada and the US are in discussions on whether to designate radionuclides as a Chemical of Mutual Concern (CMC) under the Great Lakes Water Quality Agreement.   If a designation were to occur, both countries would need to work on reducing human releases of radionuclides into the environment, or unintentional exposure from products that contain radionuclides, such as some medical equipment. There is no timetable for when another round of additional CMCs could be named, though a list is in development.

kevin bunch
Kevin Bunch

Kevin Bunch is a writer-communications specialist at the IJC’s US Section office in Washington, D.C.

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