Utility Kyushu Electric Force turned on a reactor at Sendai, around 1,000 kilometers (620 miles) southwest of Tokyo, at 10:30 am (0130 GMT).
The 31-year-old reactor - working under harder post-Fukushima security rules - was relied upon to achieve full limit around 11:00 pm Tuesday and would begin creating force by Friday.
Business operations are to start ahead of schedule one month from now, an organization representative said.
The restart comes over four years after a shake started wave activated emergencies at the Fukushima plant, provoking the shutdown of Japan's steady of reactors and setting off a pitched fight over the future utilization of nuclear force.
The mischance sent radiation over a wide territory and constrained countless individuals from their homes - a significant number of whom will probably stay away for the indefinite future.
Decommissioning of the injured Fukushima reactors is relied upon to bring decades with remuneration costs - barring the expense of the site's tidy up - now besting $57 billion.
Against atomic assumption still runs high in Japan and TV indicated nonconformists fighting with police before the Sendai plant, which is on the southernmost principle island of Kyushu.
Nearby media said in regards to 200 dissidents accumulated at the site, including previous head administrator Naoto Kan who has turned into a prominent hostile to atomic lobbyist.
The asset poor country, which once depended on atomic force for a quarter of its power, restarted two reactors briefly to encourage its needs after Fukushima. Be that as it may, they both went disconnected from the net by September 2013, making Japan totally atomic free for around two years. (AFP)