CHRIS UHLMANN: Imagine living in a place with more radiation contamination than Fukushima, by some measures, more than Chernobyl.

Now imagine living there for decades, as the Government did everything it could to hide the truth, and deny the devastating impact on health.

That's what has happened to hundreds of thousands of people near the Russian city of Chelyabinsk.

The region's home to one of the Soviet Union's first atomic weapons complexes, and also the site of one the world's worst nuclear disasters.

But don't be surprised if you've never heard of it.

Moscow correspondent Norman Hermant reports.

NORMAN HERMANT: To illustrate the ravages of Soviet industrial policy it's hard to go past the scarred landscape of Chelyabinsk, on the eastern side of the Ural Mountains. So many defence and heavy industries were crammed here until the late 1980s the whole region was off limits to foreigners.

About 80 kilometres north there was a model city not found on any maps. Known variously as city 40, Chelyabinsk 65 and now Azursk, it is still closed to outsiders. It was built to house the workers at Mayak, one of the USSR's most secret nuclear facilities, one that is still leading a devastating legacy.

NORMAN HERMANT: All over this region a third generation of severely handicapped children is being born. Demosa Kodochnikov (phonetic) suffers from infantile cerebral paralysis. His family has no doubt that it's linked to radiation contamination but they don't have the money for tests to prove it.

They've given up hope the Government will acknowledge any connection.

TATYANA KODOCHNIKOVA, MOTHER (translated): This is just unrealistic. I do not want to even think about that. That will never happen in my life.

NORMAN HERMANT: Milana Rodina is mentally challenged and was born with hyperkinetic disorder. Her muscles tense from day to night and she's in constant motion for nearly every waking minute.

VALENTINA RODINA, GRANDMOTHER (translated): They're are many people with cancers. I think all the nervous diseases that a lot of local people have are linked with radiation.

NORMAN HERMANT: In 1948 the USSR was racing to build its atomic arsenal and the Mayak reactor began producing the plutonium for the first Soviet nuclear bombs.

For the next two decades huge quantities of radioactive waste were dumped directly into a river and lakes.

Today they remain officially off limits.

ANDREY TALEVLIN, 'FOR NATURE' ADVOCACY GROUP (translated): As soon as the factory was set up they just started dropping radioactive waste straight into the river and they dropped in much more than Chernobyl.

NORMAN HERMANT: People still live on the banks of the river despite massive contamination after a nuclear waste tank exploded in 1957. At least 400,000 people were directly affected but almost no one was told the river had become deadly.

GILANY DAMBAYEV, 'FOR NATURE' ADVOCACY GROUP (translated): People were walking up here to cross over to go to school, to work. The children were fishing and swimming over there.

NORMAN HERMANT: Despite potentially lethal radiation levels in the Techa river, villages weren't evacuated for decades. There were no wells for drinking water, people had to rely on the poisoned river. Genetic mutations soared. Environmentalists say this many people living in such a contaminated region for so long amounts to nothing less than a medical experiment.

DR GULFARIDA GALIMOVA, MUSLUMOVO CLINIC (translated): It turned out that the Chernobyl disaster triggered us to examine the people after which we started figuring out what kind of things had happened here. At first we thought it was a mere accident. Later it turned out it was a radioactive dump.

NORMAN HERMANT: As the evidence stacked up, the Government finally started moving people in Muslomovo away from the river into a new village two kilometres down the road. But that has done little to make life easier for families here. 15-year-old Kamile is another child with a severe mental handicap.

He is one of more than 22,000 cases that the Government has reluctantly confirmed is connected to contamination.

His mother reads from the official documents that prove it.

MOTHER OF HANDICAPPED SON (translated): The disease is linked with the contaminated area. So contaminated and all of that sort of thing, it's linked with that.

NORMAN HERMANT: Despite proof of a link, there's no money to treat her son and their pensions barely cover the rent on the new house they were moved into.

In some towns residents are convinced the Government's strategy is to wait until there's no one left alive to make any claims.

Gulshara has become an activist in Karabolka another village that straddles the contaminated Techa river. In 1957 there were almost 5,000 people living here, now there are fewer than 300 and many are sick.

GULSHARA IZMAGILOVA, ACTIVIST (translated): They gradually died. They are sick, they are just tired. You can't dig yourself a grave when you're still alive. Here it's a way they exist here and die.

It's impossible to talk.

NORMAN HERMANT: A simple walk down the road tells the story. First a neighbour whose two year old daughter's cancerous tumour has come back for the third time. Her father is desperately searching for money for the latest operation.

There are numerous houses here where people are bed ridden, unable to walk for decades. It's a common condition for those who used to swim regularly in the river.

And then there are the people living here with mental disabilities. Gulshara says most of the children born here, if they survive, have some sort of handicap.

GULSHARA IZMAGILOVA (translated): For 54 years we are like experimental rabbits living on the land because scientists come and wonder how a human can possibly live on such a contaminated land where you can't even take a single step.

NORMAN HERMANT: The cemetery may hold the answer about life here. It's filled with the graves of those who have died too young. Most of the deaths will never be officially linked to radiation from one of the world's worst nuclear disasters that remains mostly hidden from Russia and the world.

CHRIS UHLAMNN: Norman Hermant with that report.