Radiation is an odourless, invisible killer, with the potential to surge through the body and tear it apart on a cellular level, irreversibly damaging DNA.

When reactor number four at the Chernobyl nuclear power plant exploded in April 1986, debris emanated radiation at a level of 10,000 roentgens per hour - enough to cause a fatal dose to anyone who stood nearby for a matter of minutes.

Firefighters made the ultimate sacrifice on April 26, absorbing unprecedented amounts of the poison as they battled to put out the enormous flames of history's most devastating nuclear accident.

As a gigantic radioactive cloud began spreading over the world - infecting 40 per cent of Europe and even stretching into northern Africa and north America - one woman found herself in the eye of the storm.

Maria Protsenko, garbed in just a blouse, skirt and sandals, was personally responsible for orchestrating the mass evacuation of Pripyat’s 45,000 civilians, emptying the devastated Soviet city of any sign of life.

She was previously the chief architect of the city, having lovingly designed neighbourhoods for young families, but in a split second she became a kind of grim reaper, sweeping away all the civilisation she had helped to create.

Recounting the fateful day to the makers of the TV series ‘Chernobyl: Inside the Meltdown’ on National Geographic, Protsenko transports herself back 40 years ago and tells of the wounds that haven’t left her.

'For the first time in my life, I was not building a city, I was burying it forever,' she said, reflecting on the scale of destruction. 'This is not only a man-made disaster, it is a catastrophe that broke the lives of thousands of people.'

By 11am the day after the explosion, a mass evacuation was announced and scheduled for 2pm, but by that point it was too late.

Some of those living closest to the power plant had already received internal radiation doses in their thyroid glands of up to 3.9Gy – roughly 37,000 times the dose of a chest x-ray – after breathing radioactive material and eating contaminated food 

Immediately after the accident, thyroid cancer was particularly rampant in Belarus, Ukraine and Russia, with 5,000 cases diagnosed among those who were children and adolescents at the time of exposure.

Today, Pripyat is an eerie ghost town of cavernous kindergartens, abandoned houses and sports halls left to decay, having been declared too radioactively dangerous for human habitation for at least 24,000 years. 

Protsenko wore no protective clothing as she led the vast evacuation operation, standing on a bridge overlooking the city while 1,500 buses picked up families district by district.

She stayed up all night designing intricate maps, allowing her to execute the mammoth task with tactical precision, not leaving anyone behind in the industrial wasteland.

'At 2pm the first bus arrived... I was standing there in my blouse and my skirt, and I had sandals on my bare feet. I had no protective gear,' she told the documentary.

Only thick sheets of lead or massive concrete blocks would have prevented her from being contaminated. 

'All that radioactive dust was rising and got on my bare feet and my legs. That's why they were so itchy. Can you imagine how much radioactive dust was flying from that place, at that time?'

But at that point, no one could understood the scale of the tragedy - not yet. 

Girls and boys played together in the street as they waited for their livesaving convoys, not yet grasping the fact that the evacuation wasn't temporary and they may never see each other again.

Many didn't have a chance to say goodbye before they vanished from each other's lives forever, turning from neighbours to refugees in one simple journey.

'We evacuated nearly 45,000 people. Without panicking and noise, we evacuated the entire city,' Protsenko said. 

She is still haunted by the memory of one woman, who watched her intensely from the bus window as she was torn away from her community.

'She didn't just look at me, she turned her head, following me with her stare.

'There was something in her face, like she was screaming inside: "What is this?! Where am I going?!"'

While she was helping the city's inhabitants escape, Protsenko had no idea she was exposing herself to so much lethal radiation.

'At that moment, I was not only not afraid, I did not even think about it,' she said.

It was only after the disaster that the architect remembered how she had spent hours absorbing the toxic fallout near the Red Forest, breathing in countless particles of contaminated dust as convoys rolled past. 

'The thing is, radiation does not make noise like exploding bombs. It does not burn like a fire. It has no smell. You do not feel it immediately, it kills quietly, slowly. And there is no awareness at all that you are in danger,' she said.

Following the evacuation, she developed a persistent cough, headaches, dryness in her mouth and intense itching in her legs - but still did not grasp that she had likely absorbed a significant dose of radiation.

Now aged 80, she's still living with the long-term impact of the disaster.

'I am no longer 40… my health is no longer what it used to be… all as a result of the radiation exposure I received long ago.'

She added: 'No one would envy it.'

While some degree of exposure was inevitable to everybody in the vicinity of the accident, the Soviet authorities didn't help matters by underplaying the tragedy in its immediate aftermath - ultimately slowing down the evacuation.

Despite the explosion in the early hours of April 26, life in the city initially continued as normal, with children outside playing and parents going about their errands, unaware that they were at the centre of a nuclear catastrophe.

'The night was clear, warm, and quiet. The residents of the city were peacefully asleep and knew nothing yet about the disaster that had occurred,' Protsenko said.

'Information about the radiation situation was kept in strict secrecy.'

When she was tasked with leading the evacuation, even she hadn't grasped the scale of the calamity, but she knew she had a job to do.

'By 6pm… we had practically evacuated the entire population of the city,' she said.

Within a few hours, it was done, and Pripyat would never be the same again.

By that time, she was one of the last people left in the uninhabitable wreckage of a town. 'The city became empty… no lights were on… it felt a little eerie.'

The Chernobyl disaster isn't contained to a single day, but went on to redefine the lives of hundreds of thousands of people all over the world.

Investigations ultimately concluded that faulty protocols in the plant's design and poorly trained personnel were responsible for the explosion, which blew the 1,000-ton steel lid off the reactor - the same weight as three 747 passenger planes. 

In the weeks and months that followed the accident, scores of firefighters, engineers, military troops, police, miners, cleaners and medical personnel - collectively known as 'liquidators' - were sent to the destroyed power plant in an effort to control the blaze and core meltdown.

In Belarus, 40,049 liquidators were registered to have cancers by 2008 along with a further 2,833 from Russia. In Ukraine, disability among the workers soared, with 68 per cent regarded healthy in 1988, compared to 26 years when only 5.5 per cent were still in good physical condition.

As well as coping with physical sickness, Protsenko is still grappling with the day to day consequences of Russian authoritarianism.

In 2022, she was forced to flee Ukraine in a wheelchair with her daughter and their kitten, following Vladimir Putin's full-scale invasion. 

And with Putin's callous disregard for safety, having launched a major offensive to capture the area around Chernobyl just days into his invasion - only to abandon it weeks later - only time will tell how far the long shadow the nuclear plant casts will stretch.

Chernobyl: Inside the Meltdown airs on National Geographic on Sunday 26th April from 4pm