By Ozaki Shuji, Kakinuma Hideyuki
Tokyo Electric Power Company (TEPCO) announced on April 25 that it plans to discharge from the seabed about one kilometer offshore treated water from the Fukushima Daiichi Nuclear Power Plant . A survey is expected to begin in September to dig an undersea tunnel for the discharge. It has been almost a decade and a half since the nuclear accident. While fishermen and others oppose the release of treated water into the ocean, the plan to do so is now taking shape.
The government and TEPCO have been considering two options: the “offshore plan,” which would discharge the water about 1 km offshore, and the “coastal plan,” which would discharge the water from the existing outlets of reactor units 5 and 6 in the coastal area. Why did they select the offshore plan?
Tritium, a radioactive material contained in the treated water, is also mixed in the wastewater generated at other nuclear power plants across the country and is discharged into the sea from the coast. This was the case at Fukushima Daiichi Nuclear Power Station before the nuclear accident in March 2011.
If the treated water is to be discharged into the ocean, the existing facilities on the coast can be used, which has the advantage of eliminating the need for large-scale additional construction. Immediately after the government decided on the ocean discharge in April this year, TEPCO mentioned the coastal plan as the first candidate during a press conference.
According to the Ministry of Economy, Trade and Industry (METI) and other organizations, however, a number of people connected with the Fukushima Prefecture hotel industry association called for the government to seek the off-shore plan out of concern for damage caused by rumors.
In response, the government and TEPCO examined the offshore plan. Although it will take more time and cost more money to construct an undersea tunnel between the plant and the release point, the offshore plan was adopted because there is almost no possibility that tritium-mixed seawater discharged offshore would be used to dilute the concentration of tritium.
However, there is a view within the government and among experts that there is no significant difference between the offshore and coastal plans in terms of safety. This is because before discharging the treated water into the ocean, the concentration of radioactive materials in the treated water is reduced by the Advanced Liquid Processing System (ALPS) to below the Japan’s national standard of 1,500 becquerels per liter, which is quite low since the WHO standard for drinking water is 10,000 becquerels per liter. (Abridged)