Japan is set to go without nuclear energy for the first time since 1970 from today, when the last operating reactor shuts down for maintenance, heightening fears of a looming power crunch this summer.

Only one of Japan's 50 reactors — at the Tomari nuclear plant in northernmost Hokkaido — is operating at present, but it is scheduled to stop for maintenance work which will last more than 70 days.

Resource-hungry Japan relied on nuclear energy for about one-third of its electricity demand until a massive earthquake and tsunami in March last year caused reactor meltdowns at the Fukushima Daiichi plant.

Utility firms managed to make up much of the power shortfalls after the nuclear accident by imposing scheduled blackouts on offices, factories and households while cranking up the use of thermal plants and gas turbines.

Since the disaster there has been lingering public distrust over nuclear energy and all but the one reactor at the Tomari plant are suspended for extra safety checks.

Workers at theTomari plant will move the control rod into reactor No. 3 at about 5:00pm (0800 GMT) on Saturday, which will lower power generation to zero, a spokesman at Hokkaido Electric Power Co. (HEPCO) said.

The long-term future of the reactor — and Japan's nuclear energy policy—remains uncertain.