Engineers were Sunday readying to refire a nuclear reactor, despite growing public protests in the aftermath of meltdowns at Fukushima, ending nearly two months in which Japan was nuclear-free.
Control rods that have prevented an atomic reaction inside Unit No. 3 at the Oi plant in western Japan were set to be removed from around 9:00 pm (1200 GMT). The reactor was expected to reach criticality nine hours later.
Hundreds of protesters blocked the road to the front gate of the power station, according to media reports, the latest in a line of increasingly vocal anti-nuclear demonstrations.
The country has been operating without nuclear power since early May when the last of its 50 working reactors was shut down for a scheduled safety check.
Restarts had put been on hold as the government mulled its options following a 9.0-magnitude earthquake and tsunami that crippled reactor cooling systems at Fukushima while more giant quakes were forecast to strike Japan.