About 150 residents from prefectures such as Fukushima and Miyagi went to court on Friday to halt the release of treated radioactive water from the crippled Fukushima nuclear plant, making it the first lawsuit of its kind.
In the suit filed with the Fukushima District Court against the central government and plant operator Tokyo Electric Power Company Holdings Inc., the plaintiffs said the water discharge, which started on Aug. 24, threatens citizens' right to live safely and hinders local fishermen's businesses.
They are also seeking nullification of nuclear regulators' approval of facilities installed for the water discharge and a ban to be placed on the release.
An additional lawsuit at the end of October is being planned.
The Japanese government began the disposal of the treated water into the Pacific Ocean, saying it is necessary to carry on with the decommissioning of the stricken reactors of the Fukushima Daiichi nuclear power plant, which was devastated by a massive earthquake and ensuing tsunami in March 2011.
Massive amounts of contaminated water have been generated in the process of cooling melted reactor fuel. The water has been kept in around 1,000 tanks installed at the site after going through a liquid processing system that removes most radionuclides except tritium.
But the containers are nearing capacity, resulting in the decision to release the wastewater, which is expected to continue for around 30 years.
The water release into the sea is "fresh misconduct" by the central government and TEPCO following the nuclear accident, Hiroyuki Kawai, a lawyer for the group of plaintiffs, told a press conference.
The Nuclear Regulation Authority said it cannot comment on the matter since it has not yet received the legal complaint, while TEPCO said it will "appropriately respond" after it has confirmed the complaint has been received.
The government has said the water discharge will be conducted safely, given that it is diluted to reduce the tritium levels to less than one-40th of the concentration permitted under national safety standards before being released into the sea.
Tritium, a radioactive isotope of hydrogen, is known to be less harmful than other radioactive materials, such as cesium and strontium.
The International Atomic Energy Agency said in a report released in July that the water discharge plan aligned with global safety standards and would have a "negligible" impact on people and the environment.
Nuclear power plants worldwide routinely release treated water containing low-level concentrations of tritium and other radionuclides into the environment as part of normal operations, according to the IAEA.