Japan's prime minister ordered workers to remain at the tsunami-crippled Fukushima nuclear plant last March as fears mounted of a "devil's chain reaction" that would force tens of millions of people to flee Tokyo, a new investigative report shows.
Then-Premier Naoto Kan and his staff began referring to a worst-case scenario that could threaten Japan's existence as a nation around three days after the March 11 earthquake and tsunami, according to the report by a panel set up by a private think-tank.
View side-by-side the progress that Japan has made since the tsunami and earthquake in March 2011.
That was when fears mounted that thousands of spent fuel rods stored at a damaged reactor would melt and spew radiation after a hydrogen explosion at an adjacent reactor building, according to the panel report.
Yukio Edano, then Japan's top government spokesman, told the panel that at the height of tension he feared a "devil's chain reaction" in which the Fukushima Daiichi plant and the nearby Fukushima Daini facility, as well as the Tokai nuclear plant, spiraled out of control, putting the capital at risk.
Kan, who stepped down last September, came under fire for his handling of the crisis, including flying over the plant by helicopter the morning after the disasters hit -- a move some critics said contributed to a delay in the operator's response.
Kan, 65, has spoken of how he was haunted by the specter of a crisis spiraling out of control and forcing the evacuation of the Tokyo greater metropolitan area, 150 miles away and home to some 35 million people.
The private Rebuild Japan Initiative Foundation report also said Japan's government withheld information about the full danger of last year's nuclear disaster from its own people and from the United States, putting U.S.-Japan relations at risk in the first days after the accident.
The report, compiled from interviews with more than 300 people, delivers a scathing view of how leaders played down the risks of the meltdowns at the Fukushima Dai-ichi nuclear plant that followed a massive March 11, 2011 earthquake and tsunami.
It paints a picture of confusion during the days immediately after the accident and says the U.S. government was frustrated by the scattered information provided by Japan and was skeptical whether it was true.
The U.S. advised Americans to leave an area within 50 miles of the plant, far bigger than the 12-mile Japanese evacuation area, because of concerns that the accident was worse than Japan was reporting.
The misunderstandings were gradually cleared up after a bilateral committee was set up on March 22 and began regular meetings, according to the 400-page report.
The report, compiled by scholars, lawyers and other experts, credits then-Prime Minister Naoto Kan for ordering Tokyo Electric Power Co., the utility running the plant, not to withdraw its staff and to keep fighting to bring it under control.
TEPCO's president at the time, Masataka Shimizu, called Kan on March 15 and said he wanted to abandon the plant and have all 600 TEPCO staff flee, the report said. That would have allowed the situation to spiral out of control, resulting in a much larger release of radiation.
A group of about 50 workers was eventually able to bring the plant under control.
TEPCO, which declined to take part in the investigation, has denied it planned to abandon Fukushima Dai-ichi. The report notes the denial, but says Kan and other officials had the clear understanding that TEPCO had asked to leave.
But the report criticizes Kan for attempting to micromanage the disaster and for not releasing critical information on radiation leaks, thereby creating widespread distrust of the authorities among Japanese.
Kan's office did not immediately respond to requests for comment on the report.
Kan acknowledged in a recent interview with The Associated Press that the release of information was sometimes slow and at times wrong. He blamed a lack of reliable data at the time and denied the government hid such information from the public.
It will take decades to fully decommission Fukushima Dai-ichi. Although one of the damaged reactor buildings has been repaired, others remain in shambles. A group of journalists, including a reporter from The Associated Press, were given a tour of the plant on Tuesday.
Workers have used tape to mend cracks caused by freezing weather in plastic hoses on temporary equipment installed to cool the hobbled reactors.
"I have to acknowledge that they are still rather fragile," plant chief Takeshi Takahashi said of the safety measures.
The area is still contaminated with radiation, complicating the work. It already has involved hundreds of thousands of workers, who have to quit when they reach the maximum allowed radiation exposure of 100 millisieverts a year.
The report includes a document describing a worst-case scenario that Kan and the chief of the Japan Atomic Energy Commission secretly discussed two weeks after the disaster.
That scenario involved the possibility of more nuclear fuel rods burning, causing the release of more radiation and requiring the evacuation of a much wider region, including Tokyo.
The report also concludes that government oversight of nuclear plant safety had been inadequate, ignoring the risk of tsunami and the need for plant design renovations, and instead clinging to a "myth of safety."
"The idea of upgrading a plant was taboo," said Koichi Kitazawa, a scholar who heads the commission that prepared the report. "We were just lucky that Japan was able to avoid the worst-case scenario. But there is no guarantee this kind of luck will prevail next time."
After the quake and tsunami struck, three reactors melted down and radiation spewed widely through eastern Japan, forcing tens of thousands of residents to evacuate from the area around the plant.
TEPCO managed to avert the worst scenario by pumping water, much of it from the sea, into Dai-ichi's damaged reactors and spent fuel pools. The reactors were stabilized by December.
A year after the disaster, however, Fukushima Dai-ichi still resembles a vast wasteland. High radiation levels hamper a cleanup that is expected to take decades.
The damaged 125-foot-tall No. 2 reactor building stands like a bird's nest of twisted steel beams. A TEPCO official who accompanied foreign media to the plant on Tuesday said metal debris was being painstakingly removed by giant cranes and other equipment as radiation doses were too high for workers.
Another challenge is keeping a new cooling system, built from a myriad of technologies and prone to breaking down, running without major glitches.
"An earthquake or tsunami like the ones seen a year ago could be a source of trouble for these (cooling) systems. But we are currently reinforcing the spent fuel pool and making the sea walls higher against tsunamis," Takeshi Takahashi, the Dai-ichi plant's manager, told reporters. "A series of backup systems is also being put in place in case one fails."
Edano on Tuesday acknowledged he had feared the worst around March 14-15. "I was working with a strong sense of crisis that under various circumstances, such a thing may be possible," he told a news conference in Tokyo.
But he defended his silence as government spokesman.
"I shared all information. Back then, I was not in a position where I, as someone who is not an expert, could irresponsibly speak about my own personal impressions and my sense of crisis," he told a news conference.
"I conveyed assessments and decisions of the government, government agencies and experts," he added.
The panel report said some of Kan's seemingly inexplicable behavior stemmed from his belief that TEPCO was going to abandon the plant and the accident would spiral out of control.
An irate Kan blasted TEPCO on March 15, yelling: "What the hell is going on" in an outburst overheard by a Kyodo News reporter and quickly reported around the globe. "I want you all to be determined," he was quoted as telling utility executives.
The utility ultimately left a corps of workers who were dubbed the "Fukushima Fifty" by media and won admiration at home and abroad as they risked their lives to contain the crisis, although their names were never formally made public.
Reuters and the Associated Press contributed to this report.
More from msnbc.com and NBC News:
- Gunmen open fire on bus in Pakistan, 18 killed
- Police evict Occupy London protesters from camp
- Syria OKs new constitution as shelling continues
- Report: Plot to kill Putin foiled
- Photoblog: Greece kicks off Lent with 'flour war'
- Report documents Iran's efforts to quell opposition heading up to elections
Follow us on Twitter: @msnbc_world