The pumping of accumulated radioactive wastewater from the Fukushima nuclear power plant is expected to take 30 to 40 years, the Tokyo Electric Power Company (TEPCO) said in a statement.
Pumping of the wastewater into the Pacific Ocean began on Thursday.
The disabled plant faced major damage in the 9.0 magnitude earthquake and subsequent tsunami that occurred in March 2011 in the northeast of Japan.
The power plant is located on an area of approximately 348 hectares in the Okuma and Futaba regions of the Fukushima province.
After the disaster, the Japanese government evacuated more than 150,000 people from a radius of 30 kilometers (18.6 miles) around the plant.
Despite the lifting of some evacuation orders since then, many residential areas have remained vacant.
The area where the water discharge is taking place is located about one kilometer off the nuclear power plant site.
The treated wastewater is being pumped through a 1-km (0.6-mi) tunnel built underwater.
TEPCO stated that the evacuation tunnel, which is built 12 meters below sea level, is resistant to earthquakes and storm waves.
The walls of the tunnel were coated with water-resistant material in two layers to reduce leakage risk and were constructed from reinforced concrete.
The aim is to mix wastewater with seawater further away from the shoreline.
Shut-off valves were installed to suspend or stop the pumping in case of emergency, in addition to pumps to increase the dilution ratio.
Officials stated that the water in the tunnel is moving at walking speed and that the discharge about 1 kilometer away from the coast takes approximately 30 minutes.
In the first stage of the evacuation, 7,800 tons of wastewater are planned to be discharged into the ocean within 7 days.
TEPCO stated that 31,200 tons of water are planned to be discharged by March 2024 and this amount is equivalent to 10 tanks. Accelerating the evacuation is planned for the future.
"Third-parties independent of TEPCO will also participate in monitoring both prior to, and after discharge, and we shall continue to cooperate with strict reviews by the IAEA (International Atomic Energy Agency) thereby thoroughly ensuring transparency," the company said in a statement on Wednesday.
Some 1.3 million tons of wastewater, which is collected in 1,046 tanks, will be discharged into the ocean using the Advanced Liquid Processing System (ALPS).
Before the wastewater is evacuated, it will undergo five different processes through the ALPS method to significantly reduce the radio-nuclide density.
Despite these processes, TEPCO stated that dilution will reduce the density of carbon-14 and tritium, which continue to be present in the wastewater, and that the density of the water, reduced to approximately 1500 Becquerels (Bq) per liter through this method, is below Japan's national security standards.
It is expected that the total tritium content in the accumulated wastewater in the tanks will be around 2.6 grams.
Thanks to ALPS, 62 radionuclides formed in pure water used to cool the reactors in the plant, except for tritium material, are separated.
According to the plan, TEPCO will dilute the liquid containing tritium, which is in line with the plan, and discharge it into the sea in periods, as the water increases day by day.
According to the information on the website of the International Atomic Energy Agency (IAEA), it is technically very difficult to separate tritium from water.
This is because water containing tritium, a hydrogen isotope, has almost the same chemical properties as water containing normal hydrogen.
Although technologies that can separate tritium from water exist when there is a high density of tritium in a small amount of water, these technologies cannot be applied to the large amount of water stored in Fukushima because it has a low tritium density.
Although the IAEA reported in July 2023 that Japan's plan to discharge accumulated wastewater into the sea complied with safety standards, researchers are concerned.
Various studies conducted after the damage at the nuclear power plant in Fukushima are thought to indicate that not only Fukushima and its surroundings but also various parts of the world could be affected by the discharged wastewater.
According to National Geographic magazine, one of the studies conducted after the disaster detected radionuclides about 9,000 kilometers off the coast of California. It is estimated that these radionuclides are transported from Fukushima by currents.
On the other hand, about 6 months after the accident in 2011, bluefin tuna carrying radionuclides from Fukushima were found off the coast of San Diego in the US.
Researchers are also concerned that radionuclides could be carried to various parts of the world due to currents and the migration of marine animals as a result of the discharge of wastewater.
The US-based National Association of Marine Laboratories said in a report the discharged wastewater may threaten the Pacific Ocean, the "largest continuous body of water on the planet, containing the greatest biomass of organisms … including 70 percent of the world's fisheries."
After the earthquake and tsunami that occurred in March 2011, damage occurred in TEPCO's 6-reactor nuclear power plant in Fukushima.
After the core meltdown occurred in reactors 1 and 3, water was pumped into them to cool the reactors. The processed and radioactive wastewater accumulated over time.
After the earthquake, the removal of all fuel rods from the spent fuel pools in reactor 4 of the nuclear power plant was completed in December 2014.
In December 2019, the government postponed the planned start of the removal of spent fuel from reactor pools 1 and 2 by five years for security reasons.
The removal of fuel rods from reactor 3 was completed in April 2021.
The facility needed water to cool the reactors within it, leading to the production of large amounts of water contaminated with radiation since the earthquake.
In May 2023, the wastewater storage tanks at the plant reached 97% of their capacity, and the annual cost of storage is estimated to be about $912 million, the daily South China Morning Post reported.
According to TEPCO, the process of decommissioning the plant and thus the evacuation of wastewater could take 30 to 40 years.
Countries like China and Hong Kong have imposed import bans on seafood from Japan. With the ongoing evacuation, it is expected that the scope of these bans will be expanded.
