Fukushima operator TEPCO said Tuesday it would ask Japan's nuclear watchdog for permission to restart reactors at the world's largest atomic power station, its first such request since the disaster two years ago.

Tokyo Electric Power Co is readying an application for the re-firing of two of the seven units at Kashiwazaki-Kariwa in Niigata prefecture in the north of Japan.

The entire power station has been shuttered since around 12 months after the tsunami-sparked meltdowns at Fukushima in March 2011.

"We decided at a board meeting to apply for the safety assessment for Kashiwazaki-Kariwa plant's reactors No. 6 and No. 7 as early as possible," company president Naomi Hirose told reporters.

The two reactors have a power generation capacity of 1.36 million kilowatts each.

All but two of Japan's 50 nuclear reactors are offline, shut down for safety checks after the Fukushima disaster, the worst the world has seen since Chernobyl.

A vocal anti-atomic campaign whose leading lights say the nuclear industry had too cozy a relationship with its regulators in the decades leading up to Fukushima, nudged the government into establishing a new industry watchdog.

Eager to prove it has teeth, the watchdog has set strict new standards that operators must show they can meet before they will be granted permission to re-start mothballed reactors.

The new rules come into force next Monday. TEPCO said it would be making its application to the Nuclear Regulatory Authority "swiftly" after that.

Japan's power companies have been badly hit by the surging cost of making electricity from fossil fuel alternatives since their reactors were shut down.

Resource-poor Japan has to import the coal, gas and oil it is using to replace nuclear generating capacity and the falling value of the yen has pushed up the relative cost of those dollar-priced commodities.

TEPCO is also struggling with the vast expense of the clean-up at Fukushima and with the mounting compensation bills for people whose lives or livelihoods were wrecked by the disaster.

The clean-up has been complicated by a series of incidents at the crippled plant, including leaks of radioactive water.

The latest problem came Tuesday when a small fire was reported near an incinerator. There was no release of radiation.

Reports of TEPCO's planned move to ask for the green light at Kashiwazaki-Kariwa sent its shares soaring on the Tokyo Stock Exchange. The issue closed up 19.12 percent at 623 yen.

Although the natural disaster of March 2011 claimed around 18,000 lives, no one is officially recorded as having died as a direct result of the meltdowns at Fukushima.

However, large areas around the plant had to be evacuated, with tens of thousands of people still unable to return to their homes.