Even then, the handful of men on the roof struggled to extinguish even the smallest blazes, caused by materials which seemed to burn more savagely when they poured water on them. These were almost certainly pellets of uranium dioxide, which, superheated to more than 4,000 degrees Celsius before the explosion, had ignited on contact with the air; when hosed with water, the resulting reaction released oxygen, explosive hydrogen, and radioactive steam.
