Citing safety concerns, the city of Hakodate in Hokkaido on Thursday sued the state and Electric Power Development Co. to halt the construction of a nuclear reactor based on mixed oxide fuel at a plant about 23 km across the sea in Oma, Aomori Prefecture.

The suit — the first of its kind — was filed with the Tokyo District Court.

The lawsuit is a sign that municipalities at risk of being seriously affected by a nuclear accident want a greater say in safety matters. After the three meltdowns at the Fukushima No. 1 plant in 2011, the central government expanded the default evacuation for all nuclear power plants to a minimum radius of 30 km instead of 10 km.

The MOX fuel to be used at the Oma plant is made from uranium and plutonium extracted from reprocessing conventional uranium fuel. It was developed as a way to dispose of weapons-grade plutonium.

Some reactors in Japan have allowed MOX to make up one-third of their cores, but no reactor in the world has ever run solely on MOX fuel.

In the suit, the city said the safety of the Oma plant could not be guaranteed even though the country has revamped its nuclear regulations since the Fukushima disaster.

Electric Power Development, the wholesaler better known as J-Power, said in March it will ask the state to assess the Oma plant’s safety as early as this fall in preparation for going online.

The state approved construction of the Oma plant in 2008, but work was suspended in 2011 in the wake of the Fukushima disaster at the Fukushima No. 1 plant operated by Tokyo Electric Power Co., leaving the facility only about 40 percent complete.

J-Power, however, resumed construction in October 2012.