An aerial view shows the Tokyo Electric Power Company's tsunami-crippled Fukushima Daiichi nuclear power plant in Fukushima Prefecture in this March 11, 2013, file photograph.

Tokyo - Technicians have restored power to all cooling systems at the reactors of Japan's tsunami-hit Fukushima nuclear plant, the operating company said on Wednesday after a blackout sparked a new crisis.

Equipment in pools used to cool used fuel became fully operational from 15h12 GMT on Tuesday - 30 hours after the blackout, Tokyo Electric Power Company (TEPCO) said.

Used nuclear fuel becomes dangerous if its temperature is allowed to rise uncontrollably to the point where a self-sustaining critical reaction begins, causing a meltdown.

The incident was a reminder of the vulnerable state of the Fukushima plant two years after the tsunami, despite the government's claim that the reactors are in “cold shutdown” and no longer releasing high levels of radiation.

The latest crisis began on Monday night with a brief power outage at a building on the plant's site that serves as the central command for work to contain the nuclear accident and to dismantle the reactors.

The initial glitch, a suspected problem with a power switchboard, cut electricity to the cooling pools at three of the four heavily damaged reactors as well as a common pool at 7pm (10h00 GMT) on Monday, according to TEPCO.

By Tuesday evening engineers had managed to restart cooling systems in the three affected reactor pools, TEPCO said. - Sapa-AFP