RADWASTE MANAGEMENT | CONTAMINATED WATER
Discharge plans for Fukushima
The Japanese government and Tokyo Electric Power Company have detailed plans to release treated radioactive water from Fukushima Daiichi about 1km off the coast via an undersea tunnel
FUKUSHIMA DAIICHI’S TREATED RADIOACTIVE WATER, which contains tritium, will be released through an undersea tunnel. The Japanese government and Tokyo Electric Power Company (Tepco) concluded that using such a tunnel would create less reputational damage than releasing the water directly at the coast near the plant. Tepco is expected to conduct a drilling survey for
geological research in September or later as the undersea tunnel needs to penetrate bedrock. It will submit the construction plan to the Nuclear Regulation Authority (NRA) by the end of September, aiming to build the tunnel by spring 2023, when the water release is planned to start. The tunnel will stretch 1km east from the plant out to sea, releasing the water into an area of the ocean where there are no fishing rights. More than 1 million tonnes of treated water has
accumulated at the Fukushima site since the March 2011 earthquake and tsunami triggered the meltdown of three reactor cores. Water pumped into the ruined reactors to cool the melted fuel, mixed with rain and groundwater, which has also been contaminated, is being treated using an advanced liquid processing system (ALPS). The process removes 62 radionuclides, including strontium and caesium, as well as carbon-14, but leaves behind tritium. While the level of radioactive tritium that remains in the
treated water will be diluted to below regulatory standards, the decision to release it well offshore into the Pacific is aimed at preventing reputational damage to local marine products, amid an outcry from fishermen. According to an official in charge of the water discharge project, Junichi Matsumoto, who works for Tepco’s
Fukushima Daiichi Decontamination & Decommissioning Engineering Co, the undersea tunnel will be constructed by hollowing out bedrock near Fukushima 5 and the water will be released at a depth of about 12m below the ocean’s surface. The controlled release, with an annual cap on radioactive materials, will continue for about 30 years, or until the plant decommissioning ends, Matsumoto said. The Japanese government said it will buy marine
products as an emergency step to support fishermen if the planned discharge of treated water from the Fukushima plant into the sea hurts their sales. Tepco plans to dilute the treated water with a large amount of seawater to reduce the tritium concentration to less than 1500 becquerels per litre. As the seawater within the nuclear plant’s port area contains radioactive materials, the water will be taken from outside the port. It had also considered directly releasing water from within the plant site to reduce the need for construction, but the diffusion of tritium remained a key concern. It said it will increase the sampling locations and frequency of tritium measurements in the area. Tepco said in a press release introducing its plan that it “would like to sincerely apologise for the great burden and inconvenience that the Tepco Fukushima Daiichi nuclear power station accident has caused on the people of Fukushima, and society as a whole”. Tepco said its response to handling treated water considered the basic policy on handling of treated water decided by the government in April. It has also been reviewing details of the design and operation of facilities for securing safety “with a view to taking thorough actions to minimise adverse impacts on reputation”. One of the ways Tepco hopes to increase confidence
in its water treatment policy is through a ‘rearing’ test of marine organisms. It plans to rear marine organisms in seawater containing ALPS treated water to show that the level of tritium in those organisms does not become more concentrated than the seawater tritium level. Tepco is also investigating possible methods for
removing tritium from the water and has selected Nine Sigma Holdings as a partner in eliciting proposals and promoting wide-scale research on tritium separation technology. An open call webpage has been set up. Proposed
Above: View of the coastline near Japan’s Fukushima Daiichi nuclear plant 36 | October 2021 |
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technologies will be evaluated by Nine Sigma Holdings and the results will be examined by Tepco. “If it turns out that the technology is able to be realistically applied to ALPS treated water, etc, detailed designs will be drawn up and verification tests of the technology will be conducted,” Tepco said. ■
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