Shrouded by forest in the southern Ural mountains, the Russian city of Ozersk offers its residents a peculiar mix of nuclear dystopia and domestic bliss. The birthplace of the Soviet nuclear-weapons programme remains a closed city, but in City 40, the Iranian-born US filmmaker Samira Goetschel and her film crew take you behind the barbed-wire fences for an unauthorized glimpse of what it was – and still is – like to live there.

Using archive footage, the 73-minute documentary (now available on Netflix in many countries) first shows how the city was created in 1945 around the Mayak nuclear plant. Then codenamed “City 40”, Ozersk was patterned on the US city of Richland, Washington, which housed the workers who produced plutonium for the “Fat Man” bomb detonated over Nagasaki, Japan. In both cities, citizens were lavished with higher-than-average salaries, along with good-quality housing, healthcare and education systems. Indeed, the most remarkable aspect of City 40 is the window it offers on the everyday lives of Ozersk residents, who were known to outsiders as the “chocolate people” during the Soviet era on account of the abundance of luxury foods available there. In one scene we see agile youths back-flipping in a park; in another we see citizens attending a theatre performance.

Meanwhile, we learn from local journalists and nuclear scientists that residents of the city suffer from high rates of cancer, with many lives cut short or damaged due to radiation-related health issues. The contrast is both uneasy and surreal. The film’s central character is a local human rights lawyer, Nadezhda Kutepova, who has long campaigned to open up the city to the outside world. At the documentary’s conclusion, we learn that since her final interview, Kutepova was accused of industrial espionage and plotting against the Russian nuclear industry, and that she and her four children have been granted political asylum in France. This, of course, raises some troubling questions about the ethics of documentary film-making, but as viewers it is hard to second-guess the relationship that developed between the film-maker and her contributors. We are, however, left with one glaring reality: City 40 may no longer be a state secret, but Russia will not be inviting the outside world for an authorized tour any time soon.

• 2016 DIG Films