"Innocent Saturday," in competition at the Berlin film festival, follows young party official Valery Kabysh as he learns of the extent of the disaster from Communist bosses who initially try and cover up what has happened.
He runs to the nearby town of Pripyat and tries to catch a train to safety with his girlfriend, but when that escape route closes he is quickly sucked back into everyday life of weddings, shopping, music and drink.
His former bandmates need a drummer and have a series of Saturday gigs booked, so Valery rejoins them as they set out to live life to the full, however short it may prove to be.
Only occasionally, as when a bridegroom remembers that he and his wife are expecting a child, does the invisible threat of radiation intrude on an outwardly idyllic day.
"What really fascinated me was the question as to why people who knew about the catastrophe did not escape the city," said Russian director Alexander Mindadze. "Perhaps because the danger was invisible?"
He added that although it happened 25 years ago, the Chernobyl disaster was still part of the psyche of people living in the former Soviet Union.
"It's true it's a sensitive topic, no doubt about it," he told reporters in Berlin on Monday after a press screening. "Chernobyl is with us in Russia and in all of us mentally, and will go hand in hand with our life and history."
Actor Anton Shagin, who played Valery, was just two at the time of the accident, but remembered how some classmates who had been close to the epicenter of the disaster would stand in a separate queue for food because of special dietary requirements.
Svetlana Smirnova-Marcinkevich, in the role of girlfriend Vera, was not born in 1986, but has met many people affected by the worst nuclear accident in history.
"My friend Marina was there at the time, as was the costume designer on the film, and they said people had no idea of what was happening and were celebrating, and only a day later were they told about the disaster and left home never to return."
Despite portraying the failure of officials to warn people of the dangers -- producer Alexander Rodniansky called it the "drama of silence, the drama of the big lie" -- Mindadze said his was not a political film.
And while the presence of danger heightened everyone's sense of life, he added that his movie was about something particular to people from the Soviet bloc -- fatalism.
"I think it's a purely Russian story," he said. "I think generally our genetic code is such that we always live very close to danger and death. In modern European countries, when something like that happened, people would run away."
Reporting by Mike Collett-White, editing by Paul Casciato