"I remember looking back at the plant after the explosion," recalls Valentina Prokopivna, then the chief librarian in the nearby town of Pripyat. "It was like looking into a furnace."
In the hours and days that followed the explosion on April 26, 1986, the burning reactor sent clouds of radioactive dust into the atmosphere, which then scattered across the world.
Along this path of radioactivity, many have since developed cancers and other diseases - although the number of casualties is still the subject of contention.
Official estimates from the three former Soviet countries affected - Ukraine, Belarus and Russia - say around 25,000 had died by 2005.
But 20 years after the accident, many of the survivor's descendants are still suffering the effects of the nuclear fallout.
Irradiated parents have also passed on problems to their offspring.
Out of the 3 million people officially recognised as victims of Chernobyl by the Ukrainian government, 642,000 are children.
Of the 3 million victims officially
recognised, 642,000 are children
"It's a problem now," continues Prokopivna, who now runs the Chernobyl Union's Children's Fund, a charity for child victims of the disaster.
"Ukraine has never fully stressed that this is not a problem of the past, but of the present," she says.
"That night, you could also see this shining light going up into the sky from the burning reactor," Prokopivna told Aljazeera.net.
"It was this strange colour. Later, my 5-year-old son developed spots on his neck that were the same colour as that light."
Nevertheless, many families have continued to live in the Chernobyl zone, despite the fact that the soil and water for 30km around the plant is still heavily irradiated.
They face the likelihood of throat cancer and serious damage to their neurological systems.
Some families in the zone have taken to selling their apartments to pay for treatment for their children, but they often succumb to their ailments.
Many families continue to live in
the Chernobyl zone
"We try to help the children who live in the zone," says Prokopivna.
"A partial solution is that we have a programme to send 350-500 of them abroad, to Italy or Germany, for two months of the year.
"There they can live somewhere healthy and the change in them is dramatic. We are always thanking God or Allah for this help - as there is only one god for this. But we need more help. What we can do is such a small drop."
On the night of April 26, Soviet-era plant managers were conducting an experiment to boost electricity output by heating up Chernobyl's Reactor No.4 beyond its normal limits.
Yuri, who was working in the plant control room that night, says he is haunted with questions of what he personally should - or could - have done.
"We were ordered to do certain things - the plant boss wanted to win a medal, as these were very popular in those days.
"So he ordered us to do things to the reactor which we knew were dangerous and which we should have stopped," he says, unwilling to disclose his surname.
Reactor No.4 was heated beyond
its limits before exploding
"But how can you disobey orders, how can you do the right thing, when the consequence of doing the right thing is that nothing happens - there is no disaster, and there is no reason apparent then for having ignored the orders?"
Yuri was lucky to have escaped. Ordered to go upstairs from the main control room to check water levels, he took the elevator to the 18th floor, took four steps forward when the doors opened and then "the reactor exploded. I turned round to see the elevator crushed, smoke everywhere".
After desperately trying to switch the plant's computers - shut down by the explosion - back on, Yuri finally realised the extent of the disaster when he looked out the window.
"There was something hypnotic about it. There was a light, a neon light glowing around the reactor in the darkness - this was in the middle of the night.
"I remember looking at this light and then deep down inside me something told me to get out of there, to go - that this light was going to kill me."
By the time he reached his home in Pripyat, 1km away, he was already suffering severe radiation sickness and fell into a coma. Two days later, the entire town of 40,000 people was evacuated.
Prokopivna, the former librarian, says: "I first got a glimpse of the scale of the disaster when I was standing outside the police station in Pripyat, at about 11pm the night after the explosion.
"I saw a whole lot of young conscript soldiers in these plastic suits come out of the police station to go up to the reactor and they were so young, all of them, and looking so scared. A man next to me said 'they're not coming back'."
Worker sweeping up radioactive
dust in April
By this stage, the town had become covered in radioactive dust, yet the authorities made no official announcement of an explosion.
Meanwhile, hundreds of soldiers, police and firemen had been drafted in to try and contain the reactor fire by pouring sand and cement over the core, which was pulsing out massive doses of radiation.
Vladimir Mashenko, at the time an army helicopter pilot, told Aljazeera.net: "We must have flown hundreds of sorties over the reactor.
"In my helicopter, we had a squad of conscripts who were pouring stuff out the back onto what was left of the reactor roof. Then there was my crew. I was the only one still alive five years later."
The radiation claims its victims with an eerie randomness. Like cancers from smoking, exceptions may live to be a 100, while others die very much younger.
It has also claimed the life of a town - Pripyat, which is still deserted today and contains pockets of high radiation.
"You are walking across your native city and it is dead and it is playing with you and you're wondering if it will take you with it"
Yuri, who was working in the plant's control room on April 26
Chernobyl plant worker Yuri, who has been in and out of hospital ever since, recalled how Pripyat residents were allowed back in September 1986 to collect their belongings.
"It was a terrible situation - to walk through my town and the only things I could hear were my own footsteps and the wind. It was a feeling I would not wish on anyone.
"You are walking across your native city and it is dead and it is playing with you and you're wondering if it will take you with it."