Published: Sep 07, 2011 4:11 PM EDT

TOKYO (AP) - Japan's former prime minister says he feared early in the March nuclear crisis that it might become many times worse than the Chernobyl disaster and threaten the nation's survival.
    
Naoto Kan says he imagined "deserted scenes of Tokyo without a single man" and the need to evacuate tens of millions of people.
    
"It was truly a spine-chilling thought," Kan said in an interview with the Tokyo Shimbun daily published Tuesday.
    
Kan said those images flashed in his mind during the first week of the crisis, when information coming from the radiation-leaking Fukushima Dai-ichi plant was sketchy and he was told that its operator, Tokyo Electric Power Co., was considering pulling out its staff. TEPCO has since said that it never planned to withdraw from the plant.
    
Kan, who resigned last week amid criticism over his administration's handling of the disaster, said when he heard that cooling systems had failed at the nuclear plant soon after it was damaged by a March 11 tsunami, he understood the gravity of the situation.
    
"The power was totally lost and there was no cooling capacity. I knew what that meant. So I thought, 'This is going to be a disaster.'"
    
Kan said crisis management at the plant failed because the emergency plans included no scenario for a total power failure.
    
Authorities have since said that the cores of three of the six reactors melted down - much worse than they said initially - spewing about one-sixth the radiation emitted by the accident at Chernobyl.
    
After a series of hydrogen explosions, Kan said he heard from then-Trade Minister Banri Kaieda that TEPCO was considering pulling out staff from the nuclear plant.
    
Without staff to cool the overheated reactors, Kan said he knew the reactors and spent nuclear fuel stored in pools would "rapidly melt down and release massive amounts of radiation."
    
He said he summoned then-TEPCO President Masataka Shimizu for an explanation, but he "never told me anything clearly."
    
"Withdrawing from the plant was out of the question. If that had happened, Tokyo would have been deserted by now. It was a critical moment for Japan's survival. It could have been a disaster leaking dozens of times more radiation than Chernobyl," he said.
    
"Japan was facing the possibility of a collapse" at that time, he said in a separate interview published Wednesday by the Mainichi newspaper. "I was under an enormous sense of crisis."
    
As Kan grew more skeptical of TEPCO's handling of the accident, he established a joint task force with the company at its headquarters four days after the crisis began.
    
At about that time, the U.S. government, which had been providing assistance from the start, was becoming frustrated, Kan said.
    
"We were not told straight out, but it was obvious that they questioned whether we were really taking this seriously," Kan said. Japan then sent a pair of helicopters to pour water over one of the reactors in a largely unsuccessful attempt to cool it down. He said the move had a "symbolic" effect that eased some concerns.
    
Because of the high radiation levels, he said officials feared there would be a shortage of workers at the plant even after their maximum radiation exposure limit was raised to 250 millisieverts from 100 millisieverts. Kan said officials considered raising the limit further, but the discussion abated as the initial critical situation eased.
    
The Fukushima complex is about 140 miles (225 kilometers) northeast of Tokyo. The greater Tokyo area has more than 30 million people.
    
Some 100,000 people from around the plant have been evacuated. While the amount of radiation leaking from the plant has dropped significantly, authorities say accumulated radiation in the soil and vegetation may make it difficult for residents to return to their homes for some time, perhaps years.

(Copyright 2011 The Associated Press. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.)