(...more on the fire, April 27, 07 hours)
The government committee discusses the necessity of evacuation of the
nearby town of Pripyat. Everyone supports evacuation except Professor A.L.Ilyin,
chairman of the Soviet Council for Radiation Protection. He thinks the
radiation situation will improve. By now, as it is understood that graphite
is burning and that radiation is being released, further steps are taken.
Firstly, extinguishing water is added. This is a dangerous mistake. Due
to the high temperature, the water separates into hydrogen and oxygen,
and this mixture of gas can explode; an explosion like this releases heat.
Thus, the fire is not extinguished, but fanned by the water. After three
fruitless attempts to extinguish the fire, the authorities decide to throw
sand, lead and boron carbide onto the reactor from helicopters. Boron carbide
can absorb neutrons and stop the uranium fissioning. Lead absorbs heat,
enabling the temperature to drop. Sand is to extinguish the fires. Between
27 April and 1 May, about 1800 helicopter flights deposit around 5000 tonnes
of extinguishing materials such as sand and lead onto the burning reactor.