The unit began generating electricity on 9 May and should be reconnected to the grid early next month. Tepco’s 16 other reactors remain offline and have yet to be given authorisation to resume operations.

The restart marks the first operation of a Tepco unit since 15 April, when Fukushima I-6 was shut down for inspection. Tepco said it was necessary to have at least 10 units back on line soon, if it is to meet the expected demand this summer.