Fukushima explained: Why Japan is releasing over a million tons of treated radioactive water into the sea
By Carl Samson
On an ordinary spring day in Japan in 2011, one of the most devastating natural disasters in modern history occurred. An undersea megathrust earthquake — with a magnitude of 9.1 — rocked the Pacific Ocean 72 kilometers (approximately 45 miles) east of the Oshika Peninsula of the Tōhoku region.
The earthquake, which lasted for six minutes, was followed by a powerful tsunami that contributed to the loss of about 20,000 lives.
The horror, however, was just beginning. About 100 kilometers (around 62 miles) south of the impact, killer waves spawned another disaster, and one that would take decades to resolve: a nuclear accident.
The event, known as the Fukushima nuclear disaster, became the world’s most severe nuclear accident since Ukraine’s Chernobyl in 1986. Today, Japan is preparing to release “treated” radioactive water from Fukushima into the Pacific, sparking concerns among critics who fear adverse consequences to both people and the environment.
However, Tokyo recently earned the blessing of the United Nations. Now, as the Japanese government prepares to pump more than a million tons of treated water into the ocean, the rest of the world wonders: How did Japan arrive at such a contentious decision? Does its plan actually meet global safety standards? And what do neighboring countries have to say?
When tragedy struck
Japan’s biggest nuclear disaster occurred at the Fukushima Daiichi Nuclear Power Plant in Ōkuma, Fukushima Prefecture, on March 11, 2011, shortly after the Tōhoku earthquake and tsunami. The incident was later classified as Level 7 on the International Nuclear Event Scale (INES), joining Chernobyl as the only two disasters to ever receive the designation.
Upon detecting the tremor, active reactors at the plant automatically shut down their normal power-generating fission reactions. The shaking also cut the plant off from the Japanese electricity grid. As a result, backup diesel generators automatically started. This power source allowed pumps to continue to circulate coolant through the reactors’ cores, which, if left unaddressed, can overheat and cause a massive steam explosion.
Unfortunately, the succeeding tsunami further complicated the situation. Peaking at 14 meters (approximately 46 feet) high, the waves swept over the plant’s 5.7-meter (approximately 18.7-foot) seawall, flooding the lower parts of the reactor buildings. This caused the backup generators to fail, which eventually resulted in three nuclear meltdowns, three hydrogen explosions and radioactive contamination. At this point, residents within a 20-kilometer (approximately 12.4-mile) radius were ordered to evacuate.
The disaster has produced radioactive wastewater, which is now primarily groundwater that naturally comes into contact with the reactor buildings. In the immediate aftermath, around 80% of the leak that reached the atmosphere had deposited over the Pacific Ocean and some rivers. On April 5, 2011, Tokyo Electric Power Company (TEPCO), which runs the plant, began discharging 11,500 tons of untreated water — the least contaminated of those it had stored — into the ocean. Another 300,000 tons were dumped the following month.
TEPCO estimates that the cleanup program to decontaminate affected areas and decommission the plant will take 30 to 40 years. To prevent further contamination of seeping groundwater, it constructed an “ice wall” that reduces the flow of groundwater into the buildings.
Radioactive wastewater is being treated under the Advanced Liquid Processing System (ALPS), which removes all radionuclides, save for tritium. Separating tritium from water is not only costly, but also technically challenging due to its chemical composition. Tritium cannot be destroyed or converted into a stable, non-radioactive form. While considered to be a relatively low-risk radioactive material, its release into the environment, even in small quantities, raises concerns due to its potential long-term effects on the human body and the ecosystem at large.
At present, TEPCO stores 1.32 million metric tons of treated water, which is stored in more than 1,000 tanks. However, space is running out. Furthermore, TEPCO cannot build more tanks if the plant must ultimately be decommissioned. On July 7, Japan’s Nuclear Regulation Authority (NRA) approved the treated water’s discharge into the Pacific Ocean, days after the United Nations’ International Atomic Energy Agency (IAEA) concluded that Japan has met global safety standards.
“Based on its comprehensive assessment, the IAEA has concluded that the approach and activities to the discharge of ALPS treated water taken by Japan are consistent with relevant international safety standards,” IAEA Director General Rafael Mariano Grossi said in a recent 140-page report. “Furthermore, the IAEA notes the controlled, gradual discharges of the treated water to the sea, as currently planned and assessed by TEPCO, would have a negligible radiological impact on people and the environment.”
Meeting international standards
The IAEA’s conclusion follows a two-year review by a dedicated task force composed of its top specialists who received advice from “internationally recognised nuclear safety experts” from 11 countries. The task force reportedly conducted five review missions, published six technical reports, met multiple times with Japanese government and TEPCO officials and analyzed “hundreds of pages of technical and regulatory documentation” before arriving at its decision.
A liter of ALPS-treated water contains 1,500 becquerels of tritium. Japan’s regulatory limit permits a maximum of 60,000 becquerels per liter, while the World Health Organization, for context, allows up to 10,000 becquerels per liter. In its report, the IAEA notes that TEPCO had undergone a radiological environmental impact assessment (REIA), which found that annual doses of treated water to representative persons (adult, child and infant) are “far below” the NRA’s recommended limit of 0.05 mSv (millisieverts) per year. Meanwhile, estimated dose rates of three marine representative fauna and flora (flatfish, crab and seaweed) are “more than 1 million times lower” than derived consideration reference levels set by the International Commission on Radiological Protection (ICRP).
TEPCO plans to release the water via an undersea tunnel that stretches for around 1 kilometer (approximately 0.62 miles) off the coast. Third parties, including the IAEA, will monitor the discharge.
“We’ll continue to provide transparency with live continuous monitoring throughout [the] treated water discharge process,” said Grossi, who also opened a field office at the Fukushima plant. “Our task is just starting — we’re here for the long haul.”
What neighbors are saying
No immediate deaths have been reported from the nuclear disaster, but concerns over the long-term effects of radiation exposure continue to be raised. The explosions reportedly injured at least 16 workers, while dozens more were exposed while dealing with the aftermath and three others were taken to the hospital due to “high level exposure.” In 2018, the Japanese government recognized the first worker death related to exposure and agreed to compensate his family. In 2021, the United Nations reported that there had been “no adverse health effects” documented among residents who are directly related to the accident but added that any future radiation-associated health effects are “unlikely to be discernible.”
Neighboring countries and territories have expressed opposition — or at least ambivalence — to Japan’s plan to release the treated water. However, some stances changed shortly after the IAEA announced its support. South Korea now officially backs the release, citing the results of its own assessment as part of its decision. Meanwhile, Taiwan says it will closely monitor the release process to ensure that it adheres to international regulations.
China, on the other hand, remains the plan’s most vocal critic. Last Friday, Tokyo urged Beijing to approach the situation in a “scientific manner.” In response, the latter asked that Japan “face up” to legitimate concerns from all sides and “sincerely” communicate with its neighbors. “This is as much an issue about attitude as it is about science,” Chinese diplomat Wang Yi said.
China has also urged ASEAN countries to oppose the release. It even asked Indonesia to stop using the term “treated water,” according to a report. So far, the ASEAN has not taken a stand on the matter. Meanwhile, the Pacific Island Forum, composed of 17 island nations in the Pacific Ocean, asked Japan earlier this year to delay the release “until all parties verify it is safe.”
Countries beyond the Asia-Pacific region have also weighed in on the matter. The G7 — which consists of Canada, France, Germany, Italy, the U.K., the U.S. and Japan itself — have shown support for the discharge plan since April. The U.S. Nuclear Regulatory Commission, for one, acknowledged that “any exposure to radiation” could pose “some health risk.” But it also pointed out that “everyone is exposed to small amounts of tritium every day.”
A 2012 study reported finding “unequivocal evidence” that Pacific bluefin tuna had transported radionuclides from Fukushima to California. For now, any opposition to the release has materialized in food bans. China has announced that it will ban food imports from 10 Japanese prefectures and vowed to run strict radiation tests on food from the rest of its neighbor. Last week, Hong Kong followed suit.
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