There's the Kyshtym disaster: https://en.wikipedia.org/wiki/Kyshtym_disaster https://en.wikipedia.org/wiki/Kyshtym_disaster The Soviets were also even less ca

There's the Kyshtym disaster: https://en.wikipedia.org/wiki/Kyshtym_disaster https://en.wikipedia.org/wiki/Kyshtym_disaster The Soviets were also even less careful than the US about tests of high nuclear yield weapons.