Craig Mazin conducted extensive research into the Chernobyl disaster and has created one of its most authentic depictions in the Chernobyl miniseries. Nevertheless, a number of licenses were taken, which he has addressed in the accompanying podcast.
- The real Legasov was married with children, and was being looked after by his wife and daughter when he committed suicide. Mazin chose not to include the Legasov family in the story, to avoid a When You Coming Home, Dad? theme that he felt would detract from the tragedy of the explosion and the various fallouts. Episode 4 acknowledges the existence of Legasov's family when Shcherbina warns Legasov they will be targeted by the KGB if he goes public about the true cause of the disaster.
- In real life Legasov himself didn't record any tapes where he revealed the truth behind Chernobyl; instead his writings were disseminated throughout the Soviet scientific community, and presumably were committed to tape at some point. He also expressed approval for how Dyatlov was punished after the incident, rather than complaining that Dyatlov should've been executed. Legasov taping his own words, and hiding them for someone else to retrieve, made for a better opening visual and setup.
- Legasov is shown hanging himself in his apartment and timing his suicide down to the minute of the anniversary of the disaster. In reality there's debate over whether he hanged himself in his home or in his office, but wherever his death took place it happened on April 27, 1988, two years and one day after the disaster.
- Radiation effects are speeded or otherwise exaggerated for story-telling purposes:
- Misha starts feeling the effects of touching graphite within seconds and develops severe blisters in his hand either several minutes or a few hours after at best. In the real account that inspired this scene, the fireman only told a doctor that his hand felt numb and swollen - and that was the day after the disaster. A plant worker is also seen with a bloodied face, although this may have been the result of regular thermal burns.
- The latter is, according to the script, Victor Degtaryenko
, who was in real life badly burned by steam coming from broken pipes in the destroyed section of the plant where Yuvchenko found and rescued him.
- The latter is, according to the script, Victor Degtaryenko
- There wasn't as much visible smoke in reality... and it was white-ish, not black. Any dark smoke that actually was produced would have been a result of the fires in the immediate aftermath of the explosion, which were largely extinguished within four hours. The change helps visualize the danger, but at the cost of not understanding why the characters keep thinking it's not as severe as it really is when huge plumes of black smoke are belching from the building.
- It took weeks for the Red Forest to turn red. In the show, it happens overnight.
- "Nuclear Tans", radiation burns resulting from direct exposure to fission material, are used to indicate characters suffering, often unknowingly, from early radiation sickness, even when the exposure was to material that would not directly damage the skin. A nurse who directs the hospital staff to remove the firefighters' outfits burns her palm in the time it takes her to carry the uniform to the basement. In reality, the risk from the uniforms was in inhaling the dust particles that had lodged on them, and they were not radioactive enough to cause burns in a short exposure (although the firefighters, having worn the uniforms soaked in water and dust all night, did develop skin-level beta burns. This was likely the least of their worries once ARS set in, however.)
- The show depicts ash from the power plant falling on the civilians gathered to look at the fire from the railroad bridge, who develop "nuclear tans" by the following morning. Neither happened in reality, but it is used as a stand-in for people receiving radiation there and developing cancer later (although how many and how much is disputed). The only people outside the plant who displayed that level of radiation poisoning were two fishermen in a canal right next to the plant.
- The Episode 5 epilogue states that it was reported everybody that was present on the "Bridge of Death" watching the reactor fire died. However, due to incomplete records and the questionable reliability of witness anecdotes, it's difficult to determine whether everybody on the bridge actually died or if the claim was merely an urban myth.
- Perevozchenko was responsive and involved with containment efforts for some hours a least, rather than succumbing right after reporting to the control room.
- Radiation burns darken the skin but appear as normal burns, not what is shown as what happened to Vasily.
- Lyudmilla and her baby were never in any real danger by staying with Vasily. Those who suffer from Acute Radiation Syndrome are still injured, but they can't spread radiation to others. Once the person's clothes are removed and their bodies are washed, the main source of contamination is no more present. Some radioactive particles from the fire were inhaled by the first responders, but the amount of radioactivity these particles emitted from inside their bodies was still not enough to harm a nearby person or cause fetal malformations. But it is consistent with the knowledge and belief at the time period.
- In the series, people in the final stages of Acute Radiation Syndrome look nightmarish, as if their skin is half dissolved. Although ARS is in many ways a horrible way to die, it has nowhere near such a drastic effect on a person's outward appearance. Survivors testified that during the acute phase their skin fell off, and it is true that Akimov literally "lost his face" in the last days before his death, so much so that he had to communicate through morse code, but the zombie-like appearance with which Vasily and Toptunov are portrayed is heavily exaggerated.
- Misha starts feeling the effects of touching graphite within seconds and develops severe blisters in his hand either several minutes or a few hours after at best. In the real account that inspired this scene, the fireman only told a doctor that his hand felt numb and swollen - and that was the day after the disaster. A plant worker is also seen with a bloodied face, although this may have been the result of regular thermal burns.
- Zharkov is fictional and the early morning meeting where he has his most poignant scene never happened.
- Bryukhanov arrived at Chernobyl at 2:30am and Fomin arrived two hours later. However, Fomin is shown having arrived first and waiting for him.
- The corridor Dyatlov walked in right after the explosion had no windows so he really couldn't have seen broken glass, let alone graphite.
- The firemen in the show are displayed having confusion and general unawareness when it comes to the nature of the fire, and especially the nature of graphite. In reality, according to witness accounts, many of the firemen present at the explosion had been present when Reactor 4 was first constructed and would know the basics at the very least, yet they still worked anyways because they might be able to save people. The show adds to the tension and mystery by having them all be unaware (although the injuries displayed all did happen, to an extent)
- Three men saw the exposed core (Perevozchenko, Kudryavtsev and Proskuryakov), but only Kudryavtsev and Proskuryakov do in the show. It is hard to justify this as a Pragmatic Adaptation, because Perevozchenko is not Adapted Out and still appears in the control room (he's the guy Dyatlov calls delusional and orders taken to the infirmary).
- Yuvchenko, having suffered serious radiation burns, undergoes something of an Heroic BSoD, asking a comrade for One Last Smoke and seemingly resigned to his fate. He's never seen again, implying an offscreen death. Whilst the Real Life Aleksandr Yuvchenko suffered horrific radiation burns and had to undergo over a year of medical treatment at a specialist hospital in Moscow, he eventually recovered enough to be discharged and even went back to work in the nuclear industry for a time. He credited his muscular build as the main reason he was able to pull through the effects of ARS. He eventually died in 2008 at the age of 47. Though the cause of death is listed as unknown, Yuvchenko was known to suffer from leukemia at the time, likely an after-effect of being at the plant that fateful day.
- Most of the work done by the plant workers to contain the consequences of the explosion is omitted.
- A lot of containment tasks that were undertaken by volunteers (examining the core, turning the valves, the miners) are depicted as being coerced at gunpoint. Mazin explained this as a case of Cultural Translation. For example, the real Sitnikov didn't need a physical guard to drag him to the floor, because going there was as much of a non-choice for him, having been born and raised in a totalitarian state that didn't offer him a hope to turn down the order. A Western audience wouldn't understand this unless fed a script-derailing Info Dump, so he included the guard as a compromise. Of course, your mileage may vary.
- Similarly: Summary execution in the Soviet Union was rarely, if ever, practised after the 1930s and the Stalin era. Shcherbina would not have threatened to have anyone shot for disobedience. He might threaten that they would lose their job and good standing with the Party, but not even the GULAG system existed at that time. In general, Soviet workers just did what they were told because the Soviet propaganda system was powerful and the workers genuinely believed, largely uncoerced, that by following the instructions of their superiors they were helping to build communism.
- Even more, the Cultural Translation merges with Historical Villain Upgrade with Bryukhanov, Fomin and Dyatlov are depicted failing to refuse to perform the test in unsafe conditions mainly due to their greediness and desire to get promoted, while in real life, the reason they proceeded without objecting the request of delaying it was because that request was made by someone who had a higher position within the CPSU. Again, in that totalitarist country, if someone with a higher position demanded to someone with a lower position to do something, the latter would have done it, period. One of the things that kept URSS together until then was this idea that for everything to work as much as possible it was necessary that everyone did whatever those who represent the CPSU ordered to do without objection.
- The miners are shown drinking while on the clock, something they never did in real life. They also never took off their clothes, no matter how wet or uncomfortable they got.
- There are at least claims that some miners took off their clothes, but without clarifying how many miners and how many clothes. The same claims insist they did only at night after the watchmen and management crew went to sleep.
- Although the helicopter accident happened exactly as shown (it is a remake of video footage), it was in October instead of April. Furthermore, the series implies it was caused by radiation, but the actual crash was due to pilot error, not radiation: the pilot lost control in the air currents around the reactor and the rotor struck a crane.
- In general, there were dozens of scientists from different disciplines working under Shcherbina, and hundreds that contributed to the government's response in some way. In the show, their work is condensed on Legasov and the Composite Character Khomyuk, which turns them into something of an Omnidisciplinary Scientist.
- In the series, Shcherbina is rude and hostile towards Legasov while they both are on a flight to Pripyat, to the point of threatening to throw him out of the helicopter, and also totally ignorant about nuclear power. In his actual tapes recorded before his suicide, Legasov remembers briefing Shcherbina and other bureaucrats about the Three Mile Island accident while flying to Kyiv (from where they reached Chernobyl by land) and describes the conversation just as "anxious" (which is hardly surprising). In general, Shcherbina definitely had an impressive experience of collaborating with scientists, since in the 1960s he was one of the first champions of oil exploration in the Western Siberia (still providing Russia with petrodollars). And Legasov was right-hand man of Anatoly Alexandrov, the President of the Academy of Sciences and a member of the Central Committee of the Communist Party (both position implied direct access to the Secretary-General). Therefore, in real life Shcherbina most likely treated Legasov with respect.
- Legasov persuades Shcherbina to evacuate Pripyat as soon as possible after the two witness citizens going about their daily lives in spite of the disaster. In real-life, it was Armen Abagian, the director of one of the Moscow nuclear-power research institutes who had been dispatched to Prypiat as a member of the government commission, who approached Shcherbina and demanded the city be evacuated.
- The series omits General Nikolay Antoshkin, who was in charge of the helicopter drops and instead gives his role to General Pikalov.
- A title card identifies Tula as being in Russian SSR (Soviet Socialist Republic). The official name of Russia under Soviet rule was Russian SFSR (Soviet Federative Socialist Republic).
- Shcherbina receives a call indicating that a power plant in Sweden has detected the radiation and now the West is aware of the disaster. This is presented as his reason for ordering the evacuation of Pripyat. However, the scene takes place on Sunday, April 27, which was indeed the date that the city was evacuated. The Forsmark Nuclear Power Plant in Sweden did not detect the radiation until the morning of April 28, after the evacuation.
- In the same call, Shcherbina says that children are not being allowed to go outside in Frankfurt. The closure of playgrounds in West Germany did not occur until a week later.
- For the three “suicide divers,” their mission was an ordinary work assignment. And they did not dive under water. And 2 of them were still alive at the time of the series' release.
- The real Mikhail Shchadov, Minister of Coal Industries, was 58 (but looked older) and more imposing than his fictional counterpart. He was an ex-miner himself who started working at 15 and he introduced a new type of open-ground mining during his tenure just to make the miners working conditions better, a far cry from the clueless Upper-Class Twit in the show. But then the introduction of the miners wouldn't be as funny.
- He also never went to order the miners personally. It all came down the proper channels.
- The miners themselves weren't the disillusioned laborers as presented in the series. Firstly, coal mining was a serious industry in Russia and was one of the major backbones of the economy, so the miners enjoyed pretty high salaries. A majority of them were ex-soldiers with strict discipline, so they didn't need to be coerced into helping with the Chernobyl incident (not that they would've been anyway, as while the Soviet Union was still a grim place to live, it was not the terror state in 1986 like it was under Stalin). Lastly, there was no mine in Tula (there are some in the Tula region, but they all had their own names). However, they were changed to better represent the working class of the Soviet Union who had been thoroughly disenchanted by their government by the 80s.
- Different sources disagree with the "Animal Control" task force: some claim that they were made of professional hunters, while others - inexperienced draftees. It is possible that there was a contingent of both types.
- When it came to writing the scenes involving Vasily and Lyudmilla Ignatenko, Craig Mazin drew extensively on the Real Life Lyudmilla’s account of the disaster as told in Svetlana Alexievich's book Voices from Chernobyl. Several months after the miniseries went to air, Lyudmila gave an interview to the BBC in which she criticized the makers both for their inaccuracies and for not approaching her directly. note
- In reality, Lyudmila was about 5 months pregnant when the accident happened but she managed to conceal it because of her thin physique, and she gave birth two months after Vasily's death. In the show, she appears to be one month pregnant or less when the explosion happens, and doesn't give birth until eight months later.
- When visiting Vasily at the Moscow hospital, Lyudmila didn't initially have to lie about being pregnant as nobody thought to ask her at first. Lyudmila did have to tell a lie of a slightly different nature, as the doctors main concern was that the radiation could render her barren. She lied, by telling them they already had a boy and a girl (and therefore did not want/need any more children) in order to allay their fears.
- When the lead doctor, Angelina Guskova, found out Lyudmila was pregnant, she expressed disapproval but did not bar her from seeing Vasily altogether. Likewise several of the nursing staff warned her of the dangers but allowed her to stay on the ward with him for extended periods out sympathy for her.
- According to Lyudmila, they actually had a good view of Moscow from Vasily's window and they even watched the May 1 fireworks together. Vasily also bribed or convinced a nurse to bring flowers for Lyudmila.
- The doctors at the Moscow hospital did actually try to save Vasily’s life. An American oncologist, Dr. Robert Gale, had voluntarily flown to Moscow to offer his services and attempted a bone marrow transplant on Vasily and several others. Sadly, it was to little avail as the majority of the transplant recipients died anyway.
- The Real Life Lyudmila’s biggest specific objection to the series is the scene where Vasily is shown screaming and writhing in agony as the ARS starts to take hold, which she says never happened in reality. However, it is worth noting that some of the doctors who treated the radiation victims (including some who identified Vasily in particular) have disputed this, saying that the victims would often remain calm around family only to scream and writhe in pain once they were gone, leaving the claim ambiguous.
- Despite her determination to be at his side, Lyudmila did miss Vasily's final moments, which is how events play out on screen. However, the real life story is possibly even more of a tearjerker. Two firefighters who had been friends of Vasily had already succumbed to the effects of ARS, and one of their widows had asked Lyudmila to accompany her to her own husband's funeral for support. In a truly heartbreaking case of No Good Deed Goes Unpunished, Vasily died whilst Lyudmila was away.
- Vasily is implied to pass away on the same night as both Akimov and Toptunov. Akimov was actually the first of the three to die, followed by Vasily three days later, and then Toptunov the day after that.
- Episode Four opens with Lyudmilla moving into her apartment in Kiev whilst heavily pregnant and later shows her going into labour whilst sat in a park bench (presumably outside her apartment block). In reality, she went into labour whilst visiting Vasily's grave at Moscow's Mitinskoe Cemetery and ultimately gave birth to Natascha in the same Hospital No. 6 that treated Vasily. She didn't get her new apartment in Kiev until after she had given birth.
- The biggest license of the series, as admitted in the podcast, is the roles of Shcherbina and Legasov as expert witnesses in the trial of Dyatlov, Fomin, and Bryukhanov. In real life they weren't there (nor was Khomyuk, who is fictional), but it makes more narrative sense to have them there as culmination of their arcs and the story than to introduce other scientists out of the blue. The script plays with a bit of Secret History here, implying that they were really there but that the Soviet government managed to "delete" their interventions in punishment for Legasov's final speech (actually based on the notes he left after his suicide).
- The idea that the radioactive lava could cause an explosion as large as the "2 to 4 megatons" described in the show is based on very flimsy evidence by Vassili Nesterenko and not taken particularly seriously by the vast majority of nuclear physicists - a steam explosion that large could only occur if pretty much the entire remains of the reactor core fell into water at the same time. In reality what the Soviets were worried about was an explosion of any size that would cause the plant to release even more radioactive material than it already was, a very bad scenario but nowhere near as catastrophic as everything within a thirty kilometer radius of Chernobyl being leveled. The explosion would certainly have destroyed the plant and released more radiation to the point that it would make the initial incident look like someone turning on a microwave three miles away, but it would not have been akin to an actual nuclear device going off and destroying the city.
- The fact that the addition of sand to the reactor helped form corium lava also meant the core melting through the base of the power plant never happened; as a lava it was sufficiently mobile to spread itself out as it flowed through pipes and corridors, losing enough heat in the process to not be a meltdown risk any more. As such, the liquid nitrogen heat exchanger installed under the plant to freeze the ground was never needed. However, surviving miners said in an interview that the chance that it would be needed was enough to justify the risk of building the tunnel and they are still proud of having done so, even if they're glad that it ultimately didn't come to pass.
- The color and nature of the airglow (the column of light that can be seen above the core during the night) has been disputed, with some, including Aleksandr Yuvchenko mentioned above, describing it as blue and laser-like. Legasov's own notes, however, document the air glow as being crimson, not blue, and more diffuse in nature, more akin to a spotlight than a laser.
- Another thing in regards to the series was that during the moments where the plant was showing black smoke from the fire, those who witness the disaster say the smoke wasn't that heavily prevalent and died off a bit afterwards, with the smoke barely being noticeable. It can be debated that the series put in this element in order to add more fear than to something we couldn't see.
- An In-Universe example occurs at the trial when Legasov, during the description of the sequence of events, describes reactor #4 as having been turned into a "nuclear bomb" due to the pileup of safety risks and oversight. The dramatic term is for the benefit of his audience, a mix of scientists and bureaucrats. In truth, however, it's physically impossible for a nuclear reactor to be turned into an actual nuclear bomb, because the type of uranium used as fuel is completely different from weapons-grade uranium. The first, smaller explosion was likely a steam explosion, caused when the water channels in the core failed and allowed the water to directly interact with the fuel, causing it to instantly superheat and expand, rupturing the core. His description of the second explosion is plausible, though in reality it isn't exactly known what caused it, due to the lack of data. Some scientists have theorized that the reactor might have briefly gone prompt critical, but the exposure of the core to oxygen (thankfully) made it explode before it could become a full-fledged nuclear bomb.
- In Episode 4, the old woman refers to the Ukrainian famine of the early 30s as the Holodomor. However, that word was virtually unknown in the Soviet Union. In fact, the famine itself was a very taboo subject until Glasnost.
- Episode 5 shows the power already going up to 1000 before the A-Z 5 button is pressed. In reality, it never went that high then, and there wouldn't have been much of a risk had the button not been pressed.
- At his trial, Dyatlov is depicted as trying to brazenly shift the blame for the accident onto Akimov and Toptunov. This is at odds with the real-life Dyatlov's public statements following the disaster. Dyatlov was adamant that none of his subordinates made any mistakes during the safety test or caused the explosion. Instead, he blamed the Soviet government for covering up the RBMK reactor's design flaws and accused them of scapegoating Akimov and Toptunov, fighting to clear their names. He also sent a heartfelt letter of condolence to Toptunov's parents, saying that he was a great employee.
- Also, while the series makes it looks as though Dyatlov deserted the control room to meet with the higher ups, he did in fact stay to assist in rescue efforts. While searching for the (later confirmed to be dead) pump operator, Dyatlov and another plant employee were hit with radioactive water from a broken pipe. The water gave Dyatlov's coworker a fatal case of radiation poisoning. Dyatlov himself, only got a little bit of the water on his shoes. This contact was enough to make Dyatlov extremely ill for weeks, and it was the true reason he had vomited and had to be carried out of the plant. Given that Dyatlov had already received a lifetime dose of radiation in an earlier nuclear accident, the fact that he was able to survive this at all meant the man was probably Made of Iron (or Lead, as the case may be...)
- While sets generally do an amazing job of representing locations of Perestroika Era USSR, most windows appear to have uPVC frame (as opposed to wooden ones, which was an almost exclusive standard for territory).
- The hasty construction of the Containment Sarcophagus (the entire reason for the biorobots and clearing the roof of the radioactive graphite) is omitted, though they do mention plans to cover the reactor with concrete.
- The omission of the Sarcophagus was explained by Mazin in a Reddit AMA as feeling more of an epilogue to the main story he wanted to tell; at that point everyone has accepted what happened and recognized the danger, so the core conflict is over.
- Episode 4 ends in December 1986, with Legasov preparing to brief the IAEA in Vienna. The IAEA post-accident conference actually took place in August.
- Also during that same conversation Legasov reveals that the flaw in the RBMK's AZ-5 emergency shutdown were discovered at a reactor in Leningrad in 1975, while certain flaws like the positive void coefficient and instability at low power were known ever since the first RBMK reactor came online, the AZ-5's "positive scram effect" was discovered a Ignalina Nuclear Power Plant in 1983 three years before the disaster. There was an accident involving a ruptured fuel channel at Leningrad in 1975, as Legasov says, but the flaw with AZ-5 wasn't noticed there, at least so far as is known.
- Episode 5 omits a key factor in the delay of the safety test. Shortly before it was due to take place, another power station had unexpectedly gone offline and the grid controller requested a delay to satisfy evening demand.
- As his character page states, Bryukhanov is portrayed advising against evacuating Pripyat but he advocated the opposite in reality. However, this was only published in English after filming had already begun. Mazin admitted that had he read this beforehand, he would have written the scene differently.
- The series epilogue states that Fomin went back to work on another nuclear plant after completing his sentence. In real life this is not true at worst and inconclusive at best. According to the available sources, he had a mental breakdown immediately following the incident and attempted to commit suicide.note He then had yet another nervous breakdown following his sentencing and attempted suicide again. His unstable mental state resulted in him only serving one year in prison, after which he was instead transferred to a mental institution, where he was locked up for the next three years. Along with Dyatlov and Bryukhanov, the new Russian state granted him amnesty in 1991 after the fall of the Soviet Union, after which point he appears to have more or less disappeared from recorded history.
