Twenty years ago in April, while the Ukrainian capital of Kiev slumbered, the operators of a nearby nuclear power station began a test. They wanted to know how long the plant could cool itself without electricity. Engineers in the control room powered down the reactor, disconnected the emergency cooling system and removed rods that controlled heat in the uranium core. They expected water trapped inside the core to keep temperatures stable. Instead, it vaporized with the force of an exploding ton of TNT. The blast of steam ripped through the plant's steel-and-cement roof in a gyre of parts and fuel; the core chain-reacted into a 9,000-degree inferno. Graphite fuel casings burst into flames and filled the night sky with a mile-high plume of... More >>>