On September 29th 1957 there was a major accident at a secret nuclear facility in the Soviet Union. Dozens of workers died and a huge cloud of radioactivity spread across the surrounding countryside. But news of the disaster was only made public decades later. Dina Newman has spoken to Zhores Medvedev, the first scientist to disclose what happened to the international community.

Photo: The Mayak nuclear reprocessing plant in 2010. Credit: European Pressphoto Agency.