By now you've probably heard of HBO's haunting mini-series Chernobyl.

It's the show everyone seems to be talking about and a few weeks ago it even took top spot on IMDb's TV show list, bumping the BBC's wildly popular Planet Earth II down to second place.

While the popularity of the five-part series has put the 1986 nuclear disaster in the forefront of people's minds, it has also left those unfamiliar with the historical events wondering just how closely the series mirrors reality.

The series' creator and writer Craig Mazin (who also wrote The Hangover parts two and three) said because the cover-up of the disaster was so deep, there were several versions of the Chernobyl story.

Mazin said he was careful not to over-dramatise the series, so most of what you see is true to the real-life accounts of those touched by the disaster.

How the show differs from real life

1. The people didn't speak English

In the early days of the series' production, actors auditioned with vaguely Eastern European accents.

In a podcast explaining each episode in the series, Mazin said he did not want to do "the Boris and Natasha" and "the Russian accent can turn comic with very little effort".

So it was decided the characters would speak with their natural accent, so long as it was not American.

Mazin felt an American accent in a Soviet story would sound silly to a US audience, and would pull them out of the story.

2. Legasov wasn't the most qualified person to head the clean-up

Actor Jared Harris alongside the real Valery Legasov. ( Supplied: IMDB/Wikimedia commons )

In reality, Valery Legasov was very high up at the Kurchativ Institute — the premier nuclear physics institute in the Soviet Union — and he specialised in radio chemistry.

He was called in to help manage the disaster because he was a zealous member of the party and someone the central committee felt it could count on to toe its party line.

But he was not a nuclear reactor expert.

"He knew a lot about radiation, and the chemistry of radioactive materials, but he was not really an expert on the function of an RBMK nuclear reactor — and a lot of other people were," Mazin said.

Scientists who helped manage the Chernobyl nuclear disaster. ( Supplied: Igor Kostin )

Those people — a dozen or so experts — actually had to help explain matters to Legasov.

Mazin decided to consolidate the many people into one. And that is how the character of Ulana Khomyuk was born.

3. There was no Ulana Khomyuk

Actress Emily Watson plays the fictitious character of Ulana Khomyuk. ( Supplied: IMDB )

The character of comrade Khomyuk, introduced in episode two, represented a group of scientists who worked to help Legasov.

Mazin said she helped to simplify the story.

"One of the other functions of the character of Ulana Khomyuk is to frankly be a little bit smarter, a little bit more aware and a challenge to him to do better," he said.

4. The helicopter crash didn't quite happen like that

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In episode two, a helicopter trying to drop sand and boron on the open reactor core flies too close and crashes.

While there was a helicopter crash in the wake of the disaster, it did not occur until a few weeks later.

The helicopter actually flew into a crane cable being used to build the sarcophagus over the exposed reactor core.

What actually happened

1. Lyudmilla Ignatenko and her firefighter husband Vasily were real people

Lyudmilla Ignatenko on her wedding day (left) and actress Jessie Buckley, who played Lyudmilla. ( Supplied: ChernobylProject/HBO )

The couple's story from the night of the explosion was inspired by a story Ignatenko recounted in the book Voices of Chernobyl, which provided the basis for many of the events depicted in the series.

Mazin said he tried to tell Ignatenko's story as accurately as he could because it was so moving and beautiful.

"I didn't really do anything to it to embellish it or change facts. I really just took what was there that she reported," he said.

"I found her story to be the most heart-wrenching of all the stories that I read because it was so much about love."

Vasily Ignatenko was a real fireman in Pripyat. He's portrayed in the series by actor Adam Nagaitis. ( Supplied: ChernobylProject/HBO )

2. Citizens were recruited to clean up

In episode three, humans dubbed "biorobots" were called in to clean up the plant by removing the extremely radioactive chunks of graphite from the reactor building's roof.

In that same episode, miners from Tula were brought in to dig underneath the plant to install machinery that would prevent lava melting through the concrete pad and contaminating the groundwater.

Then, in episode four, men were drafted in to kill all of the remaining radioactive pets that Pripyat residents had been forced to leave behind.

This was all true to history. The World Health Organisation has estimated that more than half a million civilian and military personnel were enlisted from across the Soviet Union in the wake of the disaster to clean up and contain the fallout.

In fact, people were sent to continue the clean-up for many years after the disaster.

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According to official records, 31 plant workers and firemen died in the immediate aftermath of the accident, but thousands more have died from radiation-related illnesses in the decades since.

The total death toll and long-term health effects still remain a subject of intense debate.

3. Doctors did try to use milk to treat radiation burns

The scene in episode two in which doctors at Pripyat hospital pour milk on patients' radiation burns was inspired by true events.

Mazin said some of the older doctors had no idea how to treat radiation burns and instead treated them as though they were fire burns (not that milk actually helps to treat fire burns anyway).

But as Mazin said: "There was a frightening prevalence of folk medicine going on".

The doctors ended up stripping the firefighters and bringing all of their radioactive clothes down to the basement of the hospital where they remain today.

4. 'We did everything right'

Aleksandr Akimov and Leonid Toptunov from HBO's series Chernobyl. ( Supplied: HBO )

In episode one, we see control board technicians Aleksandr Akimov and Leonid Toptunov intimidated by their boss Anatoly Dyatlov into carrying out a test despite it going against protocol.

Akimov coaches Toptunov, who was relatively new to the job, to carry out Dyatlov's orders.

When the reactor core explodes, Akimov repeats over and over to Toptunov: "We did everything right".

It was something Akimov repeated later in the series in recounting the night of the explosion to Khomyuk from his death bed.

The phrase was something that Akimov was documented to have actually said, and became important for Mazin to include in the series.

"Little lines like that, they make me feel something when they happen in the show because we are essentially reproducing truth there," he said.

What the show didn't mention

1. Chernobyl continued to operate up until 2000

A technician monitoring nuclear reactor number three in a control room of Chernobyl in May, 1988, two years after reactor four exploded. ( Reuters )

The Chernobyl power plant contained four nuclear reactors and when reactor four exploded, the other three continued functioning in the days, weeks and months that followed.

The power plant was only shut down in 2000.

At the time of the disaster, the Chernobyl plant was the linchpin of Ukrainian power and powered most of Kiev.

"If they shut it all down without any other preparation, that's devastating to an entire city, an economy, an industry," Mazin said.

The aerial view of the decimated reactor four. ( Reuters: YK/AS )

2. The fate of the miners

Another real event element fact of history the show touches on, but does not make clear, is that the miners who dug underneath the reactor, exposing themselves to significant amounts of radiation, did so in vain.

Soon after the explosion, there were fears the uranium fuel from the reactor core would get so hot and reactive that it would melt the cladding around it, turning it into a lava which could then burn through the concrete padding below and contaminate the groundwater.

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In episode three, Soviet politician Boris Scherbina and Legasov go to a mine in Tula, south of Moscow, to enlist the help of the miners there.

In reality, about 400 miners from Tula and Donbass, in Ukraine, were brought in to dig underneath the pad to put in a cooling mechanism that would use liquid nitrogen (all of the liquid nitrogen in the Soviet Union) to cool the space above it and reduce the heat of the lava.

But the reactor never melted through the concrete pad, meaning the miners were unnecessarily exposed to deadly radiation levels.

As for whether they dug the tunnels naked, Mazin said there were varying accounts of how much clothing the men took off.

"But more than one state that took it all off… And the truth is that it really didn't expose them that much more because the danger at that point [wasn't really going to make much of a difference]."



3. Legasov's tapes… and family

Legasov's narration during the series was not just a device for the show — he actually did record his memoirs on tapes.

While their contents were not as flowery and thematic in real life, Legasov did spell out his concerns about the Soviet nuclear industry.

Another aspect of Legasov the show did not touch on was that he had a wife and children.

Mazin decided not to include the family because he wanted the story to be about Legasov's efforts in Chernobyl and his relationships with the people he was fighting along with.

"I just didn't want to have those scenes of [him coming home], because the family that's left behind in these sort of wartime movies inevitably descend into a kind of whininess," Mazin said.

"And I didn't want to do that to them."