As community concerns mount, scientists explore alternatives to dumping treated nuclear wastewater into rivers and oceans

David Lochbaum is grappling with a problem with nearly no viable solutions at hand.

Since the Indian Point nuclear power plant closed in April 2021, he has been tasked with assessing alternatives to discharging treated wastewater into the Hudson River. The water—about 4.9 million liters currently stored on-site in tanks—was used to cool nuclear fuel rods when the plant was operating and spent, or used, fuel rods removed from the reactor. Although this water will be processed to remove most radioactive contaminants, a hydrogen isotope called tritium remains, along with trace levels of other radioactive elements.

“I never for a moment thought tritiated water was going to be the most debated issue,” says Lochbaum, an independent expert on the Indian Point decommissioning oversight board and a former director of nuclear power safety with the nonprofit group Union of Concerned Scientists.

Because tritium is chemically identical to the other isotopes of hydrogen, it is hard to separate. The radioactive isotope can easily enter the human body when people drink tritiated water (an analog of H₂O containing a tritium atom), consume contaminated fish or other food items, or inhale tritium when it’s in the air. But nuclear power plant managers dilute and test the wastewater before releasing it to ensure that levels of tritium and other radioactive elements meet federal safety standards. Once the treated water enters rivers and oceans, the levels become diluted further and are considered nontoxic.

Despite the low levels, environmental activists and some concerned residents near the plant worry about potential harm from any amount of radioactive waste entering the Hudson. Others fear that the discharges may drive down local real estate values and drive away the sailors, swimmers, and kayakers who flock to the area in the summer.

In Massachusetts, South Shore and Cape Cod residents raised similar concerns about such wastewater entering the bay and its impacts on wildlife and the seafood industry when the Pilgrim Nuclear Power Station ceased operating in 2019. More recently, local fishermen, neighboring countries, and some scientists have questioned the Japanese government’s decision to release treated wastewater from its ravaged Fukushima Daiichi nuclear plant into the Pacific Ocean.

But nuclear power plants have routinely released treated and diluted wastewater into water bodies over the decades they’ve operated. “People may not have been aware these discharges were taking place,” says Neil Sheehan, a spokesperson for the US Nuclear Regulatory Commission.

Given some plants’ checkered environmental and safety records, lack of transparency and trust may also worry local communities, Lochbaum says. The lack of rigorous science in these decisions to release treated wastewater stands out to Timothy Mousseau, biologist at the University of South Carolina. “We really don’t know enough about how tritium behaves in the environment [at diluted levels] to assess potential long-term consequences to the environment, to the food chain, and ultimately to humans,” he says.

For now, Holtec International, the company in charge of decommissioning the Indian Point and Pilgrim plants, has been denied permission to dump the wastewater into the Hudson and Cape Cod Bay. Holtec spokesperson Patrick O’Brien asserts that the discharges are “well within safe limits” and pose no environmental or health risks. Nonetheless, evaluating alternative disposal options may be next.

The trouble with tritium

Tritium, which is at the heart of the debate, is produced naturally in small quantities in the atmosphere and occurs in trace amounts in groundwater. In pressurized water reactors such as those at Indian Point and Pilgrim, this mildly radioactive form of hydrogen comes from the nuclear transformation of boron that’s added to water to control nuclear activity.

In water, tritium can bond with oxygen and replace the lighter isotopes of hydrogen, converting H₂O to tritiated water (HTO). “For all intents and purposes, it’s water; it just happens to be radioactive,” says Ian Fairlie, a UK-based radiation biologist and independent consultant on radioactivity in the environment. The similarity between tritiated and regular water makes it hard to separate the titrated form.

At Indian Point, Lochbaum found that tritium accounted for over 99% of the radioactivity in the treated wastewater tested before discharge between 2005 and 2021. In the Hudson River, the tritium levels were well below federal drinking-water limits of 20,000 picocuries per liter and weren’t building up over that period. Federally mandated testing of soil, vegetation, fish, and locally produced milk showed similar results.

In animal studies, scientists have found that tritium induces mutations in DNA, damages cellular apparatus, impacts fertility, and causes cancer. “Unfortunately, almost all of these studies have been done in the laboratory using quite high exposure levels,” Mousseau says. “It’s very difficult to extrapolate to what the consequences might be in an environmental setting where the levels are much, much, much lower.”

In Lochbaum’s opinion, treat and release is the best disposal option at hand for the tritium-laden water at Indian Point. But, he adds, the concerns are legitimate.

Exploring options

Lochbaum has evaluated a number of options.

One approach, similar to the one used at the Three Mile Island Nuclear Power Plant after the 1979 disaster there, is to use an electric heater to evaporate the tritiated water. According to Lochbaum, evaporating a gallon of treated water at Indian Point will result in a tritium concentration 500 times as high in the air as the level if the water were discharged into a river. Even if these levels are well within federal safety limits, “I’d rather have 500 times less tritium in the water,” he adds.

Another option is to continue storing the water in the tanks on-site until much of the tritium has decayed—rendering the water less radioactive—and then discharging it. Tritium has a half-life of 12.3 years, which means the radioactivity of tritiated materials such as HTO will be halved in about 12 years. But maintaining storage tanks and preventing leaks is challenging and expensive, Fairlie says. “Tanks will probably rust during their lifetime.”

NorthStar, a company currently responsible for decommissioning the shuttered Vermont Yankee nuclear plant, is choosing a different option. The company will be shipping 2 million gallons of treated wastewater via tanker railcars to a disposal facility in Grand View, Idaho. “Once there, they combine it with a clay-like material, it solidifies, and they then dispose it in the ground,” Sheehan says. “You’re talking about many, many shipments; it’s an intensive process.”

Some companies are developing detritiation systems, which concentrate and then remove tritium from the water. “But it’s very high cost and very energy intensive,” Lochbaum says.

While nuclear scientists and federal agencies continue to investigate better wastewater disposal strategies, “finding a way that’s both as safe as possible but as acceptable as possible is of interest,” Lochbaum adds. “Because having one or the other doesn’t seem to be working.”