When the film was first released on 16 March 1979, nuclear power executives soon lambasted the picture as being "sheer fiction" and a "character assassination of an entire industry". Then twelve days after its launch, the Three Mile Island nuclear accident occurred near Harrisburg, Pennsylvania.
The first script for the film was written in the mid-1970s. Michael Douglas initially wanted to produce this film immediately after One Flew Over the Cuckoo's Nest (1975). Jack Lemmon agreed to play his role as early as 1976. Douglas was enormously grateful to Lemmon, as he remained ready to start work at very short notice for over a year before production started, in the process passing up other work. To return the favor, Douglas amended the shooting schedule to allow Lemmon to attend rehearsals for the Broadway play Tribute (1980), the film version of which would later star Lemmon.
Producer Michael Douglas creatively demanded a harsh realism for the film by not having any music score on the soundtrack except for the Stephen Bishop's theme song "Somewhere in Between".
The event about the "bothersome whistleblower" having his car run off the road while transporting important evidence about a nuclear facility's lax/illegal/unethical/shoddy safety practices is a reference to Karen Silkwood, who was killed under similar circumstances.
The model for the control room of the plant was based upon the control room at the Trojan Nuclear Power Plant in Rainier, Oregon (along the Columbia River). At the time, it was the only nuclear plant in the US to offer tours that included a tour of the gallery that looked down into the control room.