Nuclear power has returned to Japan's energy mix as the first reactor to be restarted since last year's earthquake and tsunami came back online.
The switch-on ended a nationwide shutdown that left the country without nuclear-generated electricity for the first time since 1970.
The reactor at a plant in Ohi, in western Japan, began generating power just ahead of the release of the final report by a parliamentary investigative commission examining the crisis that the tsunami touched off in Fukushima, which suffered meltdowns, explosions and massive radiation leaks.
After the tsunami, all of Japan's working reactors were gradually taken offline for maintenance or safety checks.
Officials say the situation at Fukushima has stabilised, although it will take decades to safely decommission and the area around it remains off limits because it is a health hazard.
Despite rising public opposition to restarts because of the Fukushima crisis, government officials and the utility that runs the Ohi plant say the reactor has passed stringent safety checks.
They say its output is needed to ward off blackouts as Japan enters its high-demand summer months.
"We have finally taken this first step," said Hideki Toyomatsu, vice president of Kansai Electric Power, which operates the plant. "But it is just a first step."
The company is hoping to restart another reactor in Ohi soon. That could pave the way for other plants around the country. In the meantime, officials have called on the nation to conserve energy.
The resumption of operations in Ohi has been hotly contested in Japan, and coming ahead of the parliamentary commission's final report has raised questions over how seriously the government is trying to learn from the Fukushima crisis. Large demonstrations against the restart have been held each week outside the prime minister's office, reflecting deep grassroots opposition. Before the crisis, Japan got a third of its electricity from nuclear plants.