Valery Legasov was the deputy director of the Kurchatov Institute of Atomic Energy, and was part of the team responsible for investigating the accident at Chernobyl. While those above him tried to cover up the cause and extent of the disaster, Legasov tried to remain open and honest about what really happened. This took a toll on him professionally and emotionally, and the day before the results of the investigation were to be announced, Legasov took his own life.
Eight years after his death, Legasov was awarded the title of Hero of the Russian Federation by Russian President Boris Yeltsin, in recognition of his courageous efforts to tell the truth about Chernobyl.

Lyudmila, wife of the firefighter Vasily Ignatenko, faced a heartbreaking two weeks watching her husband die in agony. She was pregnant at the time and ignored the hospital's orders to stay away from her beloved, so when she gave birth some months later the baby died soon after birth, being diagnosed with cirrhosis of the liver and congenital heart disease.
It is believed that Lyudmila still lives in Ukraine.

In 1976, Shcherbina became a member of the Central Committee of the Communist Party of the Soviet Union and kept the position until his death.
In 1984, he became vice-chairman of the Council of Ministers and as such was in charge of dealing with the Chernobyl disaster outcome in 1986, acting as crisis management supervisor.
In 1990, he opposed election of Boris Yeltsin into chairmanship of the Supreme Soviet of the RSFSR, describing him as "a man of low moral qualities", whose election would "pave the way for the darkest period in our country's history." (Was he wrong?) However, Yeltsin was elected and later became the first President of independent Russia.
Shcherbina died in Moscow in 1990, aged 70
Source: Wikipedia

Vasily Ignatenko, husband of Lyudmila, was one of the many firefighters that were first on the scene of the roof fire, unaware of the true extent of the situation. Coming face to face with the exposed reactor, Vasily and many of his colleagues would soon succumb to the symptoms of extreme radiation sickness, and he died in hospital 2 weeks later.
Lyudmila spoke to Belarusian journalist Svetlana Alexievich about the tragic circumstances of Vasily's death.
"He started to change; every day I met a brand-new person," she said. "The burns started to come to the surface. In his mouth, on his tongue, his cheeks - at first there were little lesions, and then they grew. It came off in layers - as white film ... the colour of his face ... his body ... blue, red , grey-brown. And it's all so very mine!"
"The only thing that saved me was it happened so fast; there wasn't any time to think, there wasn't any time to cry. It was a hospital for people with serious radiation poisoning. Fourteen days. In 14 days a person dies."
"He was producing stools 25 to 30 times a day, with blood and mucous. His skin started cracking on his arms and legs. He became covered with boils. When he turned his head, there'd be a clump of hair left on the pillow. I tried joking: "It's convenient, you don't need a comb." Soon they cut all their hair."
"I tell the nurse: "He's dying." And she says to me: "What did you expect? He got 1,600 roentgen. Four hundred is a lethal dose. You're sitting next to a nuclear reactor."

Akimov was the shift supervisor on the night of the disaster. When he first received news that something was wrong, Akimov didn’t believe it. He even relayed false information to his superiors for several hours — a terrible mistake that he made up for later that night.
When he finally realized the gravity of the situation, he stayed behind to do everything he could to mitigate it. Akimov was the one who declared an emergency as soon as the reactor was shut down, though by then the damage had already been done. The reactor had exploded and was exposed, leaking extremely high levels of radiation.
Rather than evacuate, Akimov stayed behind. He had his crew turn on the emergency feedwater pumps to flood the reactor, but the power source was no longer active. Along with several of his fellow engineers, Akimov stayed in the poisonous air in the reactor building, manually pumping emergency feedwater into the reactor without any protective gear.
Akimov died two weeks later due to ARS.
Source: All That's Interesting

The Chernobyl liquidators were the civil and military personnel who were called upon to deal with consequences of the disaster on site. The liquidators are widely credited with limiting both the immediate and long-term damage from the disaster.
Surviving liquidators are qualified for significant social benefits due to their veteran status. Many liquidators were praised as heroes by the Soviet government and the press, while some struggled for years to have their participation officially recognized.
Source: Wikipedia

Bryukhanov, the plant manager, arrived at 2:30 a.m. Akimov reported a serious radiation accident but an intact reactor, fires in the process of being extinguished, and a second emergency water pump being readied to cool the reactor. Due to limitations of available instruments, they seriously underestimated the radiation level. At 3 a.m., Bryukhanov called Maryin, the deputy secretary for the nuclear power industry, reporting Akimov's version of the situation.
Maryin sent the message further up the chain of command, to Frolyshev, who then called Vladimir Dolgikh, who called Gorbachev and other members of the Politburo. At 4 a.m., Moscow ordered feeding of water to the reactor. As Director of the Chernobyl site, Bryukhanov was imprisoned for ten years but only served five years of the sentence due to illness.
Source: Wikipedia

Anatoly Dyatlov was the deputy chief engineer who supervised the test that lead to the explosion. At the moment the reactor power slipped to 30 MW, he insisted the operators continue the test. He overrode Akimov's and Toptunov's objections, threatening to hand the shift to Tregub (the previous shift operator who had remained on-site), intimidating them into attempting to increase the reactor power.
After the explosion, despite seeing the fuel and graphite scattered around, he still believed the reactor was intact. At 5 a.m., he got sick and together with Gorbachenko went to the medical unit.
After the disaster, Dyatlov was sentenced to 10 years in prison for his role in the explosion but he was released after serving 5. In 1995, he passed away from heart failure.
Source: Wikipedia

Mikhail Gorbachev, who is played by David Dencik in the series, was the eighth and final leader of the Soviet Union.
Gorbachev faced worldwide condemnation for failing to issue an immediate statement about the disaster, it wasn't until 18 days later that he finally told the rest of the world exactly what had occurred at Chernobyl.
Widely considered one of the most significant figures of the second half of the 20th century, Gorbachev remains the subject of controversy. The recipient of a wide range of awards—including the Nobel Peace Prize—he was widely praised for his pivotal role in ending the Cold War, curtailing human rights abuses in the Soviet Union, and tolerating both the fall of Marxist–Leninist administrations in eastern and central Europe and the reunification of Germany. Conversely, in Russia he is often derided for not stopping the Soviet collapse, an event which brought a decline in Russia's global influence and precipitated an economic crisis.
Today, 88-year-old Gorbachev still operates in Russia's political circles.
Source: Wikipedia

The commander of the Chernobyl liquidators, Tarakanov gave inspirational and motivational speeches to more than 3,000 liquidators who had risk it all to clear the roof.

Chief engineer Fomin arrived in the block 4 control room at 4:30 a.m. Akimov reported an intact reactor and explosion of the emergency water feed tank. Fomin kept pressing the staff to feed water to the reactor and transferred more people to unit 4 to replace those being disabled by radiation.
After Dyatlov left, Fomin ordered Sitnikov, his replacement, to climb to the roof of unit C and survey the reactor; Sitnikov obeyed and received a fatal radiation dose there; at 10 a.m., he returned and reported to Fomin and Bryukhanov that the reactor was destroyed. The managers refused to believe him and ordered continued feeding of water into the reactor; the water, however, flowed through the severed pipes into the lower levels of the plant, carrying radioactive debris and causing short circuits in the cableways common to all four blocks.
Later, before trial he had a mental breakdown and tried to kill himself. Fomin had broken his glasses and slit his wrists with the shards. The trial was delayed because of Fomin's mental breakdown, but he, along with Viktor Bryukhanov and Anatoly Dyatlov were sentenced to 10 years in a labour camp. Like the others, he didn't serve a full sentence due to health reasons and it is unclear what happened to him after his release.
Source: Wikipedia