After 57 days without nuclear power, energy-short Japan restarted its first reactor since the accidents at Fukushima Daiichi.Before last year's earthquake and tsunami blacked out the six-unit Tokyo Electric Power Co. plant, the country's 50 reactors provided nearly 30 percent of its electricity. Public opposition and local political resistance following the accidents, though, eventually kept all of the undamaged units offline after inspections and maintenance outages over the course of the year following the accident.Facing power shortages and predictions of economic damage, Japan's government has encouraged the restart of reactors, and unit 3 at Kansai Electric Power Co.'s Ohi plant is the first to come back into service. The Daily Yomiuri reported that it achieved criticality at 6 a.m., local time, Monday. Despite protests near the plant, it is expected to begin generating power today and to resume full operation Sunday.According to a KEPCO release, testing on Ohi unit 4 was schedule to resume once unit 3 comes back online. The utility hopes to start unit 4 in mid to late July.