Most of us have heard about the Fukushima nuclear disaster, an accident at the Fukushima Daiichi Nuclear Power Station on the coast of Japan caused by a magnitude 9.0 earthquake and tsunami in 2011. A feature article in Hakai Magazine looks at the current state of affairs at the plant and a very important dilemma: what can be done with the hundreds of thousands of tonnes of radioactive wastewater stored at the site?
Where does the contaminated wastewater come from? During normal nuclear reactor operations, water is used to cool the fuel and avoid overheating and meltdown. When the earthquake and subsequent tsunami hit the Fukushima plant, power was lost, and the cooling systems stopped working, causing a meltdown. Radiation was released to the atmosphere and water contaminated with radioactive isotopes was released into the Pacific Ocean. The accident is one of the only two nuclear accidents to receive a Level 7 event classification on the International Nuclear Event Scale, the other being the Chernobyl disaster of 1986. Water has been pumped into the ruined buildings for almost 10 years to keep the site cool, generating a huge volume of radioactive wastewater, with no way to dispose of it.
The Tokyo Electric Power Company (TEPCO), owner of the plant, uses the site as a storage area with tanks for the contaminated water. As of 2020, the tanks hold over one million tonnes of water, and TEPCO will run out of space by 2022, while the water piles up. According to the company, there could be up to 62 different radioactive elements in the wastewater, including cesium-137 and strontium-90, at levels that exceed safe limits despite cleaning steps. The water undergoes treatment before it is stored. It is first filtered through resin beads which attract radioactive isotopes. Afterwards, most of the water is treated further, including an advanced liquid processing system (ALPS) that removes charged particles. Not everything is removed, tritium, an isotope of hydrogen, is left in the water; it is not known to be harmful, but its effects at large doses are unknown.
The disposal options involve diluting the radioactive water, since toxicity depends on the dosage. An expert panel looked into options and narrowed them to two: controlled vapor release into the atmosphere, and controlled discharges into the ocean, and advised Japan’s government that the second one was preferable. The International Atomic Energy Agency said in April of this year that both options are technically feasible and routinely used by operating nuclear power plants worldwide under specific authorisations. Marine chemist and oceanographer at the University of Victoria, British Columbia, Jay Cullen, notes that not discharging the water also has some risks, as storing it on site, “you risk potential uncontrolled release due to another natural disaster or human error.”
If it receives approval, TEPCO would release the water in the tanks offshore Fukushima slowly over several decades. Anticipating potential impacts on human health or marine ecosystems is not straightforward, especially since TEPCO has been vague about the list of radioactive elements still in the water. So far, neighbouring countries have expressed concern, and Korea has banned seafood imports from the area. Local fishers, who had to rebuild their industry after seafood exports from the area were discontinued after the accident, also oppose ocean release. Japan is expected to announce soon their decision on the wastewater’s disposal.