Anyone in Western Europe who is over 40 will remember when Chernobyl blew up and melted down in 1986. It could have put a damper on my consumption of Dandelion Wine but I renamed it Chateau Dandelion et Strontium and chugged down all 30 bottles anyway. People of my mother's generation would have had similar memories of Kyshtym 29 years earlier, if they had known about it at the time. Russians would have called it Кыштымская авария (Kyshtym accident, crash, wreck, glitch) if they had known, but the vast majority of them were kept ignorant of the disaster until decades later.
This was because it happened at a secret location in the Urals where the Russians were developing their nuclear energy/missile program. So secret that the actual location of the accident, the Mayak plant next to the New City of Ozyorsk, didn't appear on any maps, so it was named after the nearest named village. It was years before people realised that the Earth was not an infinitely capacious toilet for our crap and the Russians had been carelessly running radio-active waste into local lakes and rivers. Then in 1953 the plants operatives started to store liquid waste in large steel tanks stored underground on a concrete plinth and capped with a 160 ton concrete lid. They knew that radioactive material gives off heat as it decays, so had installed a cooling system round each group of tanks. It must have been Boy-Chemist's Heaven in the Mayak plant because they were not only tricking about with a variety of fissile materials but also had access to such reg'lar explosives as Ammonium Nitrate which were all stored together.
On 29 September 1957, the cooling system failed and nobody noticed until there was a tremendous bang as some overheated Ammonium Nitrate exploded. The double-decker-bus-sized lid blew into the air on a plume of hot gas loaded with radioactive caesium-137 and strontium-90. They estimated afterwards that the explosion was modest enough was (about 100 tons of TNT equivalent) but, unlike the 5x larger Sailor Hat, it was a dirty bomb and the wind carried its radioactive load at least 300km to the North-East. The Russians were as casual about the welfare of their indigenous people as the Americans were about the Native North Americans and it took a while for them to get round to evacuating some 20 villages housing 10,000 people. We can with 100% hindsight chid them for this cavalier attitude but my reading of the radioactive dose (40-500 mSv, depending on how close they were to ground zero), is that it was tolerable. The notes for my Environmental Chemistry class (about a reliable as something you heard in the pub) suggest that 250 mSv in a single jolt will significantly reduce your white blood cell count, while 1000 mSv will up your chance of cancer by 5%. I probably took on-board 40 mSv from the hot wine. Anyway, such a mishap was definitely an own-goal in the Cold War Cup and the whole thing was hushed up. I daresay they would have wanted to do the same with Chernobyl a generation later, but the wind was in the opposite direction that weekend and the radio-active sophistication of everyone had increased considerably. So the Swedes noticed that the air was hot and had figured out where it was coming from long before there was any official acknowledgment from the Ukraine.
Apparently the CIA knew all about Kyshtym within the year, but kept quiet about it so that the great American public wouldn't go all wobbly on their own nuclear program. It required the ex-Soviet (they revoked his passport) dissident biologist Zoares Medvedev to lay out the nature and extent of the disaster in New Scientist in 1977. He was sufficiently near the inner circle, and a key player in samizdat circulation, to know the details and having left the country was free to spill the beans, albeit 20 years after the fact.
Kyshtym was a "level 6" incident. The third most serious that the planet has experienced:
Level 7 Fukushima Daiichi March 2011
Level 7 Chernobyl April 1986
Level 6 Kyshyma September 1957
Level 5 Three Mile Island March 1979
Level 5 Chalk River December 1952
And in case my Irish readers start flapping about the Windscale fire across the water in Oct 1957, I can tell you that it is in the ha'penny place. A trifling 20 kCi (Kilocuries) of radioactivity was released there, while the Kyshtym explosion popped off 100x more: 2MCi. And that was in the ha'penny place compared to the amount (120MCi) that the Soviet Nuclear program dribbled into Lake Karachay from the Mayak plant over the years. And if you use a microwave oven, a sandwich toaster, a hair-drier then it's all your fault.