The Nuclear Regulation Authority (NRA) of Japan has given formal approval to the plan of the Tokyo Electric Power Company (Tepco) to discharge into the sea treated water from the disabled and deactivated Fukushima Daiichi nuclear power plant (NPP). The operational reactors at the plant had been wrecked by the devastating tsunami which hit north-eastern Japan, following a massive undersea earthquake, in 2011.

Following the consequent meltdowns of the three reactors, water was used to cool the melted nuclear fuel. That, and other contaminated water, has been stored in a tank farm, containing some 1 000 tanks, constructed on the NPP site. The water is being treated, using an Advanced Liquid Processing System (ALPS). This removes all the radioactive contamination, except for tritium (which is a radioactive isotope of hydrogen).

The tank farm has a maximum capacity of 1.37-million cubic metres of water. Tepco expected this to be reached by the middle of this year, but it wasn’t, and the company now expects all the tanks to be full by the middle or later part of next year. Hence the need to discharge the water that has been treated. The company plans to discharge it into the sea, and over a period of 30 years, to massively dilute the tritium and so avoid harm to people and the environment. (The seawater dilution process will start before the water is actually discharged into the ocean.)

Tepco’s plans have been subject to independent evaluation by the International Atomic Energy Agency (IAEA), to ensure that they meet the agency’s safety standards. The IAEA stated that the amount of tritium in the water will be significantly lower than the safety limits in national regulations and in the World Health Organisation’s drinking water standards.   

“By this [NRA] approval, safety of the installation of the ALPS-treated water discharge facility has been confirmed,” highlighted the Japanese Foreign Ministry in a statement. “Nevertheless, this does not mean that Tepco can immediately start the discharge of the ALPS-treated water into the sea. Before doing so, remaining processes, such as NRA’s Pre-Service Inspections to check and confirm the installation status of the discharge facilities, will continue. The discharge of the ALPS-treated water into the sea will not start until after these steps are duly taken. The IAEA will continue to conduct its independent review throughout, including while these steps are taken, and the Government of Japan will carefully consider the findings and observations from the IAEA review.”