Japan halted the restart of Kashiwazaki-Kariwa, the world’s largest nuclear power plant, just one day after it resumed operations. The plant, located in Niigata province, had been offline since the 2011 Fukushima disaster. Its operator, Tokyo Electric Power Company (Tepco), said an alarm from the monitoring system went off during the reactor startup procedures on Thursday. "We don’t expect this to be solved within a day or two. There is no telling at the moment how long it will take," said site superintendent Takeyuki Inagaki. "We will for now fully focus on trying to identify the cause of what happened." Tepco spokesperson Takashi Kobayashi told AFP that because the problem would take time to fix, they safely reinserted the control rods in a planned way. The control rods help control the nuclear reaction by slowing or stopping it. He added, "The reactor is stable and there is no radioactive impact outside." Only one of the plant’s seven reactors was restarted. Japan shut down all nuclear plants in 2011 after a massive earthquake and tsunami caused the Fukushima meltdown. Now, Japan wants to cut fossil fuel use and reach carbon neutrality by 2050. The Kashiwazaki-Kariwa restart is a key move in this plan. However, local opinion is split. About 60% oppose restarting the plant, while 37% support it, a September survey showed. Opposition groups claim the plant is on an active seismic fault and have submitted petitions with nearly 40,000 signatures to Tepco and the Nuclear Regulation Authority.