One of the reactors at the Ohi nuclear power plant in central Japan on Sunday will go back online.
It will be the first to do so since reactors went offline due to safety concerns after the Fukushima accident last year.
All nuclear reactors in Japan are now offline.
New safety regulations were called for after the accident in March at the Fukushima plant. The government says the regulations are now just being met.
Operator Kansai Electric Power Company has been making preparations for the restart since the government decided on June 16th to resume the No.3 and No.4 reactors at the plant in Fukui Prefecture.
The company plans to start lifting control rods in the No.3 reactor at 9:00 PM in the presence of senior vice industry minister Seishu Makino and Ohi Town Mayor Shinobu Tokioka.
The reactor is expected to reach criticality, starting a self-sustaining chain reaction, early on Monday.
The utility says the reactor will start generating power on Wednesday, and begin operating at full capacity 4 days later.
The facility was shut down about 15 months ago.
The operator says it plans to restart the No.4 reactor as early as July 17th for full-capacity operations by the 24th.
The Ohi plant has been under strict around-the-clock monitoring since June 16th. Nine minor problems have been reported since then, including an interruption in the power grid monitoring signal.