Tokyo (CNN) -- The worst may have passed in the most serious nuclear accident since Chernobyl, but cleaning up when it's finally over is likely to take decades and cost Japan an untold fortune.

A six- to nine-month horizon for winding down the crisis, laid out by plant owner Tokyo Electric Power this week, is just the beginning. Near the end of that timeline, Japan's government says it will decide when -- or whether -- the nearly 80,000 people who were told to flee their homes in the early days of the disaster can return.

Friday marks six weeks since the March 11 magnitude-9.0 earthquake and subsequent tsunami that triggered the crisis.

Some of those who have already spent six weeks in emergency housing, like Tomioka funeral director Kazuhiro Shirato, say they don't expect to return to what was home.

"I've been told by TEPCO since I was very small that the nuclear power plant was safe, so I never imagined this would happen," Shirato told CNN. "I hope now that the whole town will move to another place and rebuild."

Many of those displaced by the disaster have spent a month living in government shelters -- sometimes just gyms -- and are running low on money. Tokyo Electric has promised to make a down payment on compensation of 1 million yen (about $12,000) per household, with the intention of sending out checks by late April.

Another 66,000 have been told to prepare for evacuations in towns where radiation readings are at levels that could increase the long-term risk of cancer for anyone who stays. That will certainly add to what is likely to be a staggering tab for the Japanese government and Tokyo Electric, the country's largest utility.

"We are mobilizing our resources in order to tackle the situation, to relieve the burdens on those people who have evacuated from the area," Cabinet spokesman Noriyuki Shikata said. "We know that it's going to cost a quite significant amount. But at this juncture, I don't think we have come to a specific kind of budget size."

The shadow cast by Fukushima Daiichi has inflicted yet-unknown losses on farmers, fishermen and shopkeepers. And looming compensation costs have darkened the future of Tokyo Electric, a $157 billion company that may be driven into some form of government receivership.

For those displaced, Japanese authorities have promised to decontaminate "as much of an area as possible," as Goshi Hosono, an adviser to Prime Minister Naoto Kan, told reporters earlier this week. But they have no decontamination plans prepared, and no real model for trying to clean up whole municipalities.

"We may be talking about something very new," Shikata said. "We will have to be creative."

The few precedents that do exist are daunting.

In Hanford, Washington, a plutonium plant built during the Manhattan Project created 43 million cubic yards (33 million cubic meters) of radioactive waste over four decades of fueling the U.S. nuclear weapons program, according to the U.S. Environmental Protection Agency. The United States is projected to spend at least $77 billion and another 30-plus years to fully decontaminate the surrounding area, according to a 2009 report by congressional auditors.

After Chernobyl -- the worst nuclear disaster to date -- the former Soviet Union and now-independent Ukraine essentially abandoned a 30-kilometer radius around the plant. A quarter-century later, a forest is reclaiming the city of Pripyat, where nearly 50,000 people lived before the accident. About 116,000 were resettled, according to the International Atomic Energy Agency, and published estimates put the cost of cleanup at more than $350 billion.

Shikata said the situation at Fukushima Daiichi was "somewhat different" than at Chernobyl, were the amount of radioactivity released was 10 times higher that is believed to have escaped from Fukushima Daiichi.

The biggest city covered by the evacuation orders so far is Minami Soma, with a population of about 70,000. The twin disasters of March 11 have already driven away most of its population, most of those remaining have been told they will be evacuating soon and the rest have been told to stand by.

"We will rebuild," said Shinkoh Ishikawa, a Buddhist monk at the Senryu temple just outside the 20-kilometer exclusion zone. "I'm confident about that because we had done the same after the second World War."

For those displaced, there are social concerns as well. For decades, the survivors of the atomic bombings of Hiroshima and Nagasaki -- known as "Hibakusha" -- complained of discrimination due to fears of radiation. Reports that evacuees from Fukushima were getting similar treatment brought a high-level chiding from Japan's chief cabinet secretary, Yukio Edano, on Tuesday.

"I would like to ask the public to understand that the radiation would not transfer from person to person by touching the person or his or her clothes," said Edano, the government's point man for the crisis.

As for Fukushima Daiichi itself, fully closing up the crippled plant may take decades, said Jack DeVine, a U.S. nuclear engineer who helped lead the cleanup of the Three Mile Island plant in Pennsylvania. There, it took about three years for engineers to get a look inside the damaged core of the reactor that suffered a partial meltdown in 1979 -- and what they found was "absolutely shocking" at the time, he said.

"A substantial amount of core had melted and burned its way into the reactor vessel, which we previously didn't know about," said DeVine, now retired. About 25 percent of the fuel assembly had melted, leaving behind a depression in the center of the core "like a giant ice-cream scoop."

Cleaning up and shutting down the damaged Unit 2 took 10 years, Devine said -- and unlike Fukushima Daiichi, little radiation was released at Three Mile Island. In Japan, workers are dealing with "essentially four Three Mile Islands," plus levels of radioactivity "which will be an impediment for all the work on-site."

"What we're hearing about over there is very, very different in that respect," he said.

CNN's Steven Jiang, Jiyeon Lee, Hiroo Saso and Asuka Murao contributed to this report.