Japan's prime minister is set to defy fierce public sentiment this weekend and order nuclear reactors back online for the first time since Fukushima, as he seeks to head off a summer energy crunch.

Yoshihiko Noda is expected to tell Kansai Electric Power (KEPCO) to re-fire two idled reactors at its Oi plant serving the industrial heartland of western Japan.

The controversial move comes amid fears that electricity demand will outstrip supply as temperatures soar and air-conditioners get cranked up, further crimping Japan's wobbly economic recovery.

Noda is due Saturday to meet Issei Nishikawa, the pro-nuclear power governor of central Fukui prefecture, which hosts the plant. Nishikawa is widely expected to tell the prime minister he is ready to accept the restarts after he received safety assurances Friday from the operator.

The nod from Nishikawa is the final link in the chain for Noda, who has become a vocal advocate of nuclear power being brought back into the energy mix for resource-poor but electricity-hungry Japan.

The country's 50 working reactors -- which along with the four crippled units at Fukushima contributed around a third of Japan's electricity before the disaster -- have been offline since the last one was shuttered in early May.

Public opposition in the aftermath of the tsunami-sparked meltdowns at Fukushima in March 2011 left Japan's political classes tip-toeing around the issue of restarts.

Radiation was spread over homes and farmland in a large area of northern Japan when the massive tsunami swamped cooling systems at Fukushima Daiichi.

No one is officially recorded as having died as a direct result of the meltdowns, but tens of thousands of people were evacuated and many remain so, with warnings some areas will be uninhabitable for decades.

Anti-nuclear sentiment among the public has run into increasingly apocalyptic warnings of power shortfalls, the most dire of which predicted Kansai's manufacturing base could see a one-fifth gap.

KEPCO has cautioned this will mean blackouts, which are expected to wallop producers already struggling against a tide of economic uncertainty and export markets stumbling under the pressure of Europe's debt crisis.

However, Noda's conviction that Japan could not do without nuclear power was not enough, forcing him to seek cover from international bodies and local politicians.

The government's own rules say reactors must pass International Atomic Energy Agency-approved stress tests designed to demonstrate they could withstand a natural disaster, and then get assent from their host communities.

Last week Noda set out the case for restarts in a televised press conference, saying they "support people's lives," but added that "I want to seek the understanding of local governments."

"Nuclear generation is an important power source (and) energy security is one of the country's most important issues," he added.

Earlier this week the mayor of the town of Oi, Shinobu Tokioka, gave his approval, after being offered safety assurances by an expert panel.

He said he believed the town "should fulfil its duty of supplying energy".

Fukui's governor is expected to fall in line after meeting Friday with the president of Kansai Electric Power, who promised continued effort towards attaining "the world's top-safety standards", Jiji Press reported.

Noda said last week a nuclear re-start was not a short-term solution and atomic power had its place in the country's future energy mix.

"If electricity fees go up due to an increasing dependence on fossil fuel, it would affect people like retailers, small- and mid-size companies and general households which are barely making ends meet," he said.

"If that leads to a hollowing out of business, it would decrease employment opportunities. The temporary operation of the reactors in summer would not secure our way of life."