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The second form of fuel was dust. Or to sound more professional, hot fuel particles (hot meaning radioactive). These particles penetrated the surfaces of walls, floors, ceilings, and were in the air. Almost all the premises of Shelter were contaminated. Later, we’ll talk about this, an especially “pleasant” fuel modification for us And the last, lava. Excepting the famous Elephant Leg, lava was discovered in many other places in Shelter, even at the lowest points of Unit 4. It spread via steam relief valves and pipes (fig. 15).
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Alexander Borovoi (My Chernobyl: The Human Story of a Scientist and the nuclear power Plant Catastrophe)