Thirteen years after the 2011 Fukushima disaster, Tokyo also reaffirmed that it sees a major rule for nuclear power in helping Japan meet growing energy demand from artificial intelligence and microchip factories.

The world's fourth-largest economy has the dirtiest energy mix in the G7, campaigners say, with fossil fuels accounting for nearly 70 percent of its power generation last year.

The government has already set a target of becoming carbon-neutral by 2050 and to cut emissions by 46 percent by 2030 from 2013 levels.

Under the new plans, renewables such as solar and wind were expected to account for 40 to 50 percent of electricity generation by 2040.

That marks a jump from last year's level of 23 percent and a previous target for 2030 of 38 percent.

Resource-poor Japan "will aim to maximise the use of renewable energy as our main source of power", according to the draft Strategic Energy Plan.

Government experts were reviewing the proposals released by the Agency for Natural Resources and Energy and it was due to be presented to the cabinet for approval.

Japan is aiming to avoid relying heavily on one energy source to ensure "both a stable supply of energy and decarbonisation", the draft said.

Geopolitical concerns affecting energy lines, from the Ukraine war to Middle East unrest, were also behind the shift to renewables and nuclear, it said.

- Imports -

Nearly 70 percent of Japan's power needs in 2023 were met by power plants burning coal, gas and oil.

Almost all must be imported, last year costing Japan about $500 million per day.

The government wants that figure to fall to 30 to 40 percent by 2040.

The previously announced 2030 target was 41 percent, or 42 percent when hydrogen and ammonia were included.

The new plans forecast a 10 to 20 percent jump in overall electricity generation by 2040, from 985 billion kilowatt hours (kWh) in 2023.

"Securing decarbonised sources of electricity is an issue directly related to our country's economic growth," Yoshifumi Murase, the head of the national energy agency, told the government's expert panel on Tuesday.

- Nuclear -

Unlike the previous plan three years ago, the new draft dropped language on reducing Japan's reliance on nuclear "as much as possible" -- a goal set after the 2011 Fukushima disaster.

Japan pulled the plug on nuclear power plants nationwide after the tsunami-triggered Fukushima meltdown, this century's worst atomic disaster.

However, it has gradually been bringing them back online, despite a public backlash in some places, mirroring nuclear power returning to favour in other countries too.

Nuclear accounts for about 20 percent of Japan's energy needs under the 2040 targets, around the same as the current 2030 target.

But that is more than double the share of 8.5 percent of overall power generation that nuclear provided in 2023.

- Too little, too late -

Hirotaka Koike from Greenpeace welcomed the new plan but said it was "too little, too late", calling for "much larger ambition" on renewables.

Japan "has committed to 'fully or predominantly decarbonised power systems by 2035' and, evidently, their current plan doesn't cut it," Koike said.

Hanna Hakko from climate think-tank E3G also called Japan's ambitions "quite disappointing".

"The power mix suggested by the government is not consistent with Japan's international commitments to tackle climate change and accelerate clean energy transition," Hakko told AFP.

"Various scenarios by energy experts show that if the government were to enact supportive policies, renewables could expand to cover between 60 to 80 percent of Japan's electricity generation mix in the latter half of 2030s," she said.