Con O'Neill as Viktor Bryukhanov, manager of Chernobyl:
O'Neill has acted in a number of British films and TV shows including Criminal Justice and the mini-series The Bible.
Bryukhanov also served a 10-year prison sentence for his involvement with the disaster. As of 2006, he was still alive and living in Kiev.
Sam Troughton as Aleksandr Akimov, night shift supervisor at Chernobyl:
Troughton is the grandson of Doctor Who star Patrick Troughton and has appeared on British shows such as Robin Hood and The Town.
Akimov was the shift supervisor of the night crew that worked the night of the disaster. He died two weeks after the accident due to high exposure to the radiation.
Adrian Rawlins as Nikolai Fomin, chief engineer at Chernobyl:
Rawlins is probably best known for playing James Potter in the Harry Potter films, but he's also appeared in a number of other films and TV series including Doctor Who.
Fomin was sentenced to a 10-year prison sentence as well. There's no clear confirmation about his status and whereabouts today.
Paul Ritter as Anatoly Dyatlov, deputy chief-engineer of Chernobyl:
Ritter is best known in the UK for his role as Martin Goodman in the show Friday Night Dinner, you may also know him as Eldred Worple in Harry Potter and the Half-Blood Prince and Guy Haines in Quantum of Solace.
Dyatlov was the engineer in charge of reactor No. 4 at the Chernobyl nuclear power plant when the disaster happened. He was eventually found guilty of criminal negligence and sentenced to 10 years in prison. He died of heart failure on Dec. 13, 1995, more than nine years after the disaster.
Stellan Skarsgård as Boris Shcherbina:
You might know Skarsgård for his roles as "Bootstrap" Bill Turner in the Pirates of the Caribbean films, Bill Anderson in Mamma Mia!, and Dr. Erik Selvig in Thor: The Dark World and Avengers: Age of Ultron...along with a lot more things!
Shcherbina was a Deputy Prime Minister in the Soviet Union and head of the special commission named to investigate the disaster. After a long illness, he died on Aug. 22, 1990, almost four years and four months after the disaster.
Jessie Buckley as Lyudmilla Ignatenko, wife of fireman Vasily Ignatenko:
Buckley has appeared on the West End and in the TV series War and Peace and Taboo.
Ignatenko is still alive today, living with her son in Kiev, but she doesn't speak about Chernobyl and her husband publicly because she "wants to get on with her life."
Jared Harris as Valery Legasov:
Harris has been in Mad Men and King George VI on The Crown, among many other things.
Legasov was a physical chemist who headed the commission that investigated the Chernobyl disaster. He died on April 27, 1988 one day after the second anniversary of the disaster.
Ralph Ineson as General Nikolai Tarakanov:
Ineson is best known for his roles in Game of Thrones, Harry Potter, The Witch, and the original BBC version of The Office.
Tarakanov, now 85, has reportedly been living with "radiation disease" for the last 33 years. He also described the casting of Ineson as a "perfect match."
And finally, David Dencik as Mikhail Gorbachev:
Dencik is a Swedish-Danish actor and has had roles in films like Tinker, Tailor, Soldier, Spy and The Girl with the Dragon Tattoo.
Gorbachev is the former first president of the Soviet Union, serving from 1990 to 1991. He won the Nobel Prize for Peace in helping end the Cold War. He's still active in politics today.
Emily Watson and her character Ulana Khomyuk were not included because Khomyuk is a fictional character.
Although, Khomyuk is meant to "represent the many scientists who worked fearlessly and put themselves in a lot of danger to help solve the situation."