Japan has restarted a reactor at the Kashiwazaki-Kariwa nuclear plant, the world’s largest facility, to help meet rising electricity demand during a global oil crisis.

The plant is among several in Japan whose spent-fuel cooling pools are nearing capacity, with industry officials warning that some could be full within five years. Only 15 of Japan’s 54 reactors have restarted since the 2011 Fukushima disaster, when a massive earthquake and tsunami triggered meltdowns at three reactors and displaced about 1.6 lakh people.