In the early hours of April 26, 1986, reactor No. 4 at the Chernobyl nuclear power station exploded. The Soviet government said nothing publicly for two days. When the admission finally came, on the evening news on April 28, it ran to a handful of words — an accident, a damaged reactor, “measures undertaken.” International news services, picking up on radiation readings drifting over Scandinavia, were already speculating about a meltdown before Moscow said anything at all.