SCIENCE – By Dennis Normile – Apr. 13, 2021 , 10:25 AM
Japan announced today it will release 1.25 million tons of treated wastewater contaminated by the wrecked Fukushima Daiichi Nuclear Power Plant into the Pacific Ocean. The government said it is the best way to deal with tritium and trace amounts of other radionuclides in the water.
“Releasing the treated water into the sea is a realistic solution,” Prime Minister Yoshihide Suga said at a Cabinet meeting endorsing the plan. “We will do our utmost to keep the water far above safety standards.” A Japanese government official later clarified that details of the release need to be worked out and approved. Gradual, trial releases could start in 2 years and might take 40 years to complete.
Industry groups and nuclear scientists say other nuclear plants have disposed of wastewater this way with minimal impacts. But environmental groups, fisheries organizations, and neighboring countries immediately condemned the decision, citing the vast amounts involved. Marine scientists expressed concerns about the possible impact of the discharge on marine life and on fisheries.
The announcement was long anticipated. Three nuclear reactors at the Fukushima plant suffered meltdowns in the wake of an earthquake and tsunami on 11 March 2011. Molten fuel debris burned through steel containment vessels and into the concrete bases of the reactor buildings. Ever since, workers have pumped water through the ruins to prevent the debris from overheating and causing further damage. They have also collected all the contaminated water: It now fills more than 1000 steel tanks crammed onto the Fukushima campus.
The only practical options for disposing of the water “are discharge into the sea and vapor release, both of which have preceding practices,” concluded a governmental advisory committee made up of academics and citizen group representatives in February 2020. Nuclear power plants the world over regularly release water containing trace amounts of tritium into the environment under monitored and controlled conditions. And vaporization ultimately took care of about 9000 tons of contaminated water resulting from the accident at the Three Mile Island Nuclear Generating Station in March 1979. The International Atomic Energy Agency (IAEA) “considers the disposal options as technically feasible and in line with international practice,” IAEA Director General Rafael Grossi said during a February 2020 visit to Fukushima.
Tokyo Electric Power Co. (TEPCO) runs the water through a complex chain of filters it calls the Advanced Liquid Processing System (ALPS). The treatment captures 62 kinds of radionuclides, but not tritium, a radioactive isotope of hydrogen with a 12.3-year half-life that occurs naturally in trace amounts in seawater and the atmosphere. It is extremely difficult to remove as it replaces hydrogen atoms in water molecules. Because tritium emits only low-energy beta particles, it poses a modest health risk. And the plan is to dilute the water until the tritium concentration is one-fortieth of what Japan allows in drinking water.
Although “the optics are terrible,” releasing the water into the Pacific Ocean is the right thing to do, says Nigel Marks, a nuclear materials scientist at Curtin University, in a statement released by the Australian Science Media Centre. By diluting, the “radioactivity can be reduced to safe levels” comparable to exposures from medical imaging and airline travel, he says.
But in addition to tritium, more dangerous isotopes with longer radioactive lifetimes, such as ruthenium, cobalt, strontium, and plutonium, sometimes slip through the ALPS process, something TEPCO only acknowledged in 2018. The company now says these additional nuclides are present in 71% of the tanks. “These radioactive isotopes behave differently than tritium in the ocean and are more readily incorporated into marine biota or seafloor sediments,” says Ken Buesseler, a marine chemist at the Woods Hole Oceanographic Institution.
The government official says the Fukushima water will be “repurified” to meet regulatory standards for these nuclides. Buesseler notes that those limits were put in place for operational nuclear power plants, not for the deliberate release of contaminated water from a nuclear disaster. “Would this open the door for any country to release radioactive waste to the ocean that is not part of normal operations?” he asks.
Shigeyoshi Otosaka, a marine geochemist at the University of Tokyo, worries about the accumulation of the isotopes in seafloor sediments, where they can get picked up by marine biota. The possibility is limited, “but it’s important to evaluate it appropriately,” he says. For one thing, the TEPCO “repurification” has only been tested on a small volume of water. The company needs to verify “whether the processing performance can be maintained for a long period of time,” he says.
Although TEPCO claims it will run out of room to store additional water by the middle of 2022, environmental organizations say there is space for additional tanks on land adjacent to the Fukushima campus. That storage would allow the radioactive isotopes to naturally decay while buying time to develop new treatment techniques.
Any additional release of radiation will come on top of the estimated 538.1 petabecquerels of radioactivity emitted into the atmosphere by the explosions that blew apart the three reactor buildings in the days after the earthquake. That amount was about one-tenth of the estimated radiation released by the Chernobyl nuclear disaster of 1986. The Fukushima radiation had a minimal impact on humans, though the precautionary evacuations did cause unexpected social and health problems.
Much of the radioactive material fell into the Pacific Ocean because of prevailing winds. Concerns over contaminated fish devastated the regional fishing industry. Demand for seafood from the region has gradually recovered, but fisheries officials fear releasing contaminated water will rekindle public fears about seafood from the region. Posted in:
Dennis Normile is a contributing correspondent in Shanghai, China.