It was believed that the three volunteer divers, Alexei Ananenko (mechanical engineer), Valeri Bespalov (senior engineer), and Boris Baranov (shift supervisor), who opened the gates in order to prevent a further catastrophic nuclear meltdown would almost certainly die from severe radiation exposure. It transpired that all three survived after a period of hospitalization, and two were still living at the release of this series. Baranov died of a heart attack in 2005.
"Open Wide, O Earth" is a common prayer at Eastern Orthodox funerals.
Craig Mazin had written the opening scene about Dyatlov remembering his son, who developed and died from leukemia at age 10 after Dyatlov himself was exposed to a dose of radiation while working on a nuclear submarine in Siberia. This scene was filmed but ultimately cut from the episode, after it was decided this backstory was not related to the story of Chernobyl.
Valery Legasov was born in Tula in 1936, when the city had fewer than 300,000 inhabitants. It is thus possible that he knew some of the Tulan miners sent to Chernobyl or their families.