Original subtitles

A Soviet dream that became a nightmare.

A disaster officials tried to cover up...

...as a brave few battled to stop radiation

spreading across the globe.

Using top secret Soviet documents

and hearing from those, who risked everything...

...this is the story of one of the world's worst nuclear accidents.

It's been eight days

since Chernobyl's fourth nuclear reactor exploded.

The core of the reactor is smouldering,

releasing large amounts of radioactive material

into the atmosphere.

Helicopters battled to stop this deadly radiation escaping

from the molten core.

The temperatures,

which we are led to believe were in excess of 2,000 Kelvin,

would annihilate anything that came into that vicinity.

So, the way to use that is to think about how we can use the heat

to melt a structure that would act as a neutron absorber.

A number of different things were tried.

It was decided to dump a lot of sand on top of the reactor core.

Temperature and radiation levels are rising.

There was a need to think about other types of element

to encase that fallout.

Lead and a rare element called boron are added to the sand.

Up to 200 drops are made every day.

They were tasked with going on what they call "bombing runs",

filling up sandbags and dropping them

through quite a narrow hole in the roof onto the reactor below.

It's incredibly dangerous work.

The entire time, the people in the helicopter were receiving

quite a high dose of radioactivity.

The reactor is leaking radiation

that's up to ten times above a lethal dose.

One of the pilots who flew over the disaster site

is Soviet Captain Alexander Maruhin.

In total, 5,000 tonnes of materials are dropped onto the reactor.

Nine days after the disaster, the temperature begins to fall

and the radiation leak suddenly drops by 99%.

But by then, the radiation leak outside the plant is huge.

Large areas of Ukraine are now highly radioactive.

The Soviet Government announced an ambitious clean-up operation.

Thousands of people are drafted in to Chernobyl

from across the Soviet Union.

Most of those were young men and they were given a job to do

without really being told the full consequences of...

...of what they were undertaking.

They become known as liquidators.

Liquidators was a Russian term to describe the people

who were engaged in the clean-up,

mostly soldiers and other military people, many of them conscripts,

brought in to do the dirty work.

Ultimately, around 600,000 people were involved

in this liquidation campaign.

This is a high-risk operation.

Working in and around the disaster site,

the liquidators risk being exposed to high levels of radiation.

2,000 roentgen is 10,000 times higher than background radiation

and many liquidators like Vladimir Kagan are sent into areas like this

with little or no safety equipment.

The liquidators were definitely inadequately equipped

for the dangers that they were facing.

The rule really was that the job had to be done,

and if there wasn't the safety equipment,

then people simply weren't given it.

Many liquidators travel miles from Chernobyl.

They move from village to village, searching for radiation hot spots.

The release of radiation from the Chernobyl disaster was so intense

that anything that came into that vicinity would've been irradiated.

Many towns and villages were affected by radiation.

Where a building was infected, it was sprayed with a decontaminant.

It was a viscous liquid that caused...

...any radiation to adhere to the side of the building.

So, the building itself became a kind of...

Almost flypaper, where irradiated material was stuck to it.

In other places, where the radiation levels were even higher,

bulldozers were sent in and entire villages were completely flattened.

Abandoned homes are searched.

Ca rs are collected.

Anything registering high levels of radiation is removed and buried.

Then, some liquidators are sent on a bleak search and destroy operation.

GUNSHOTS

You needed to remove all the livestock

and much of the wildlife as well because it was radioactive.

GUNSHOTS