Reactor 3 at the Tomari nuclear power plant in Hokkaido has the dubious distinction of being the last of the nation's 54 commercial reactors still in operation. But come May 5, it, too, will be taken offline, Hokkaido Electric Power Co. said Monday.

Reactor 3 was slated to be halted in late April, but Hokkaido Electric decided to postpone the shutdown for about a week because of trouble at its thermal power plant, which serves as an alternative power source, officials said.

The announcement follows Tokyo Electric Power Co.'s closure of its last running reactor early Monday as safety concerns linger from the disastrous meltdowns last March at Tepco's Fukushima No. 1 nuclear plant.