Yoshio Ichida is recalling the worst day of his 53 years: 11 March, when the sea swallowed up his home and killed his friends. The Fukushima fisherman was in the bath when the huge quake hit and barely made it to the open sea in his boat in the 40 minutes before the 15-metre tsunami that followed. When he got back to port, his neighbourhood and nearly everything else was gone. "Nobody can remember anything like this," he says.

Now living in a refugee centre in the ruined coastal city of Soma, Mr Ichida has mourned the 100 local fishermen killed in the disaster and is trying to rebuild his life with his colleagues. Every morning, they arrive at the ruined fisheries co-operative building in Soma port and prepare for work. Then they stare out at the irradiated sea, and wait. "Some day we know we'll be allowed to fish again. We all want to believe that."

This nation has recovered from worse natural – and manmade – catastrophes. But it is the triple meltdown and its aftermath at the Fukushima nuclear power plant 40km down the coast from Soma that has elevated Japan into unknown, and unknowable, terrain. Across the northeast, millions of people are living with its consequences and searching for a consensus on a safe radiation level that does not exist. Experts give bewilderingly different assessments of its dangers.

Some scientists say Fukushima is worse than the 1986 Chernobyl accident, with which it shares a maximum level-7 rating on the sliding scale of nuclear disasters. One of the most prominent of them is Dr Helen Caldicott, an Australian physician and long time anti-nuclear activist who warns of "horrors to come" in Fukushima.

Chris Busby, a professor at the University of Ulster known for his alarmist views, generated controversy during a Japan visit last month when he said the disaster would result in more than 1 million deaths. "Fukushima is still boiling its radionuclides all over Japan," he said. "Chernobyl went up in one go. So Fukushima is worse."

On the other side of the nuclear fence are the industry friendly scientists who insist that the crisis is under control and radiation levels are mostly safe. "I believe the government and Tokyo Electric Power [Tepco, the plant's operator] are doing their best," said Naoto Sekimura, vice-dean of the Graduate School of Engineering at the University of Tokyo. Mr Sekimura initially advised residents near the plant that a radioactive disaster was "unlikely" and that they should stay "calm", an assessment he has since had to reverse.

Slowly, steadily, and often well behind the curve, the government has worsened its prognosis of the disaster. Last Friday, scientists affiliated with the Nuclear and Industrial Safety Agency said the plant had released 15,000 terabecquerels of cancer-causing Cesium, equivalent to about 168 times the 1945 atomic bombing of Hiroshima, the event that ushered in the nuclear age. (Professor Busby says the release is at least 72,000 times worse than Hiroshima).

Caught in a blizzard of often conflicting information, many Japanese instinctively grope for the beacons they know. Mr Ichida and his colleagues say they no longer trust the nuclear industry or the officials who assured them the Fukushima plant was safe. But they have faith in government radiation testing and believe they will soon be allowed back to sea.

That's a mistake, say sceptics, who note a consistent pattern of official lying, foot-dragging and concealment. Last week, officials finally admitted something long argued by its critics: that thousands of people with homes near the crippled nuclear plant may not be able to return for a generation or more. "We can't rule out the possibility that there will be some areas where it will be hard for residents to return to their homes for a long time," said Yukio Edano, the government's top government spokesman. "We are very sorry."

Last Friday, hundreds of former residents from Futaba and Okuma, the towns nearest the plant, were allowed to visit their homes – perhaps for the last time – to pick up belongings. Wearing masks and radiation suits, they drove through the 20km contaminated zone around the plant, where hundreds of animals have died and rotted in the sun, to find kitchens and living rooms partly reclaimed by nature. "It's hard to believe we ever lived here," one former resident told NHK.

Several other areas northwest of the plant have become atomic ghost towns after being ordered to evacuate – too late, say many residents, who believe they absorbed dangerous quantities of radiation in the weeks after the accident. "We've no idea when we can come back," says Katsuzo Shoji, who farmed rice and cabbages and kept a small herd of cattle near Iitate, a picturesque village about 40km from the plant.

Although it is outside the exclusion zone, the village's mountainous topography meant radiation, carried by wind and rain, lingered, poisoning crops, water and school playgrounds.

The young, the wealthy, mothers and pregnant women left for Tokyo or elsewhere. Most of the remaining 6000 people have since evacuated, after the government accepted that safe radiation limits had been exceeded.

Mr Shoji, 75, went from shock to rage, then despair when the government told him he would have to destroy his vegetables, kill his six cows and move with his wife Fumi, 73, to an apartment in Koriyama, about 20km away. "We've heard five, maybe 10 years but some say that's far too optimistic," he says, crying. "Maybe I'll be able to come home to die." He was given initial compensation of one million yen (£7,900) by Tepco, topped up with 350,000 yen from the government.

It is the fate of people outside the evacuation zones, however, that causes the most bitter controversy. Parents in Fukushima City, 63km from the plant, have banded together to demand that the government do more to protect about 100,000 children. Schools have banned soccer and other outdoor sports. Windows are kept closed. "We've just been left to fend for ourselves," says Machiko Sato, a grandmother who lives in the city. "It makes me so angry."

Many parents have already sent their children to live with relatives or friends hundreds of kilometres away. Some want the government to evacuate the entire two million population of Fukushima Prefecture. "They're demanding the right to be able to evacuate," says anti-nuclear activist Aileen Mioko Smith, who works with the parents. "In other words, if they evacuate they want the government to support them."

So far, at least, the authorities say that is not necessary. The official line is that the accident at the plant is winding down and radiation levels outside of the exclusion zone and designated "hot spots" are safe.

But many experts warn that the crisis is just beginning. Professor Tim Mousseau, a biological scientist who has spent more than a decade researching the genetic impact of radiation around Chernobyl, says he worries that many people in Fukushima are "burying their heads in the sand." His Chernobyl research concluded that biodiversity and the numbers of insects and spiders had shrunk inside the irradiated zone, and the bird population showed evidence of genetic defects, including smaller brain sizes.

"The truth is that we don't have sufficient data to provide accurate information on the long-term impact," he says. "What we can say, though, is that there are very likely to be very significant long-term health impact from prolonged exposure."

In Soma, Mr Ichida says all the talk about radiation is confusing. "All we want to do is get back to work. There are many different ways to die, and having nothing to do is one of them."

Economic cost

Fukushima: Japan has estimated it will cost as much as £188bn to rebuild following the earthquake, tsunami and nuclear crisis.

Chernobyl There are a number of estimates of the economic impact, but thetotal cost is thought to be about £144bn.

Safety

Fukushima: workers are allowed to operate in the crippled plant up to a dose of 250mSv (millisieverts).

Chernobyl: People exposed to 350mSv were relocated. In most countries the maximum annual dosage for a worker is 20mSv. The allowed dose for someone living close to a nuclear plant is 1mSv a year.

Death toll

Fukushima: Two workers died inside the plant. Some scientists predict that one million lives will be lost to cancer.

Chernobyl: It is difficult to say how many people died on the day of the disaster because of state security, but Greenpeace estimates that 200,000 have died from radiation-linked cancers in the 25 years since the accident.

Exclusion zone

Fukushima: Tokyo initially ordered a 20km radius exclusion zone around the plant

Chernobyl: The initial radius of the Chernobyl zone was set at 30km – 25 years later it is still largely in place.

Compensation

Fukushima: Tepco's share price has collapsed since the disaster largely because of the amount it will need to pay out, about £10,000 a person

Chernobyl: Not a lot. It has been reported that Armenian victims of the disaster were offered about £6 each in 1986