Nuclear disaster site plans controlled release of radioactive water
Scientists say disposing of the water a little at a time is better than the alternative
The Tokyo Electric Power Company began construction on facilities at the end of July to release 1.37 million tons of radioactive water from the Fukushima Daiichi nuclear power plant into the ocean as soon as 2023. In 2011, an earthquake and tsunami destroyed the cooling mechanisms in the reactors at Fukushima, causing a nuclear meltdown. Since then, TEPCO, which owns the plant, has been working with the Japanese government, the International Atomic Energy Agency, and independent contractors to clean up the mess. But the proper way to dispose of radioactive waste has been hotly debated for decades—and Fukushima will likely be an important testbed for new techniques and technology.
TEPCO said that it must release the water because the plant is running out of storage space and because it’s risky to continue to store the water on land. But fishermen near where the water would be released worry that it will contaminate their fishing ground—or, at the very least, damage their reputation. Environmental groups like Greenpeace that oppose nuclear activity argue that the fishermen just got their ocean back after the disaster, and releasing the water will take it away again.
The damaged reactors need water pumped over them to keep them cool. Groundwater and rainwater also gather in the compromised structures that house the defunct reactors, and that water must be pumped out so it doesn’t seep back into the ground and cause further contamination. All told, the damaged plant creates about 170 tons of radioactive liquid every day that is stored in about 1,000 tanks on the site. A filtering system has removed most of the radioactive material from the water except tritium, a radioactive form of hydrogen that is harmful to humans only in large doses. No existing technology can remove it.
Benedict Jaeschke has been an environmental radiation consultant for 10 years and helps manage waste from nuclear sites. Before that, he studied the effects of tritium on marine life as part of his Ph.D. in ecotoxicology. While extreme amounts of concentrated tritium can harm marine life, something as diluted as the tritiated water at Fukushima would act like a bucket of red dye dumped off of a pier—you can see it for maybe a few seconds, but after that, it’s indistinguishable from the rest of the water.
TEPCO is not doing something new or uncommon, according to Don Seaborg, a professional engineer with almost 50 years of nuclear project experience. TEPCO has filtered the water, taking out radioactive materials like cesium and strontium that are very harmful to the environment and have a long half-life. Tritium changes the makeup of water by replacing a hydrogen atom with a tritium isotope of hydrogen—in essence making radioactive water, Jaeschke said.
Since the technology to separate tritium from hydrogen in water doesn’t exist, TEPCO plans to release the water at 1/40 the concentration allowed by the government. TEPCO held public hearings to take questions and concerns from the fishermen in the area. But Seaborg said there are risks to continuing to store the water too. If another tsunami were to damage the storage containers, that tritiated water could be released into the ocean without being diluted at all.
Jaeschke has studied submerged biota—the flora and fauna of the region—in water with high concentrations of tritium and recorded the results. In these experiments, he said he used an extremely high concentration of tritium over a long period of time that was difficult to maintain even in controlled conditions. In those studies, the tritiated water harmed the environment in some ways. But it would be difficult for the wastewater at Fukushima to recreate that experiment. He said even if the plant dumped all the tritiated water into the ocean without diluting it, the water would spread out evenly throughout the ocean. It may take some time, but unless it’s dumped in a bay where there is little water movement, high concentrations of tritium would not cause lasting damage before dispersing.
The tritium could contaminate some fish, but the same principle applies. Since tritiated water acts just like regular water, if a fisherman put a contaminated fish in a bucket of clean water, within a few hours or days, the tritiated water would disperse evenly throughout the bucket through osmosis, making the levels of tritium in the fish negligible. “These things by their nature decay and disperse,” Jaeschke said. Tritium also has a relatively short half-life, only about 12.5 years. So the water that was first stored after the nuclear meltdown has almost reached it, and the water being released will be around for a short time compared to other chemicals, Jaeschke said.
The IAEA says that the Fukushima disaster is second only to Chernobyl in the extent of its damage, and TEPCO estimates it will take another 50 years to finalize the cleanup. Releasing the tritiated water is only the first step in removing waste. Since cleanup crews could not survive working near the reactors, and normal robots would stop working within minutes of exposure to the radiation, Veolia Nuclear Solutions, a U.S. manufacturer, is developing robots resistant to the radiation to help clean up the mess. Fukushima must continue to run water over the reactors until they are decommissioned. Then, TEPCO will have to decide what to do with the reactor fuel, and the questions will continue.
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