The danger scenarios at Zaporizhizhia
Writing in Down To Earth, Dr. M.V. Ramana explains the various meltdown risks at the besieged Zaporizhizhia six-reactor nuclear power plant in Ukraine, currently caught up in war fighting:
“Broadly speaking, there are three scenarios that might result in the expulsion of radioactive materials from some facility at the Zaporizhzhia complex.
“The first is the damage to one of the reactors from a direct hit by a rocket or missile.
“The second is damage to one of the pools of water where spent fuel — the radioactive nuclear fuel that has been removed after it has generated electricity — is stored for cooling.
“The third possibility could result even without any direct attack on Zaporizhzhia: If the electricity supplied to the plant is interrupted and the plant loses all backup means to generate electricity.
“The last might seem the most unusual but the underlying reason for that possibility is the same as the other two scenarios. Any irradiated fuel contains large quantities of radioactive fission products. These elements are produced when each nucleus of uranium or plutonium breaks apart to produce energy.
“Besides being a source of harmful radiation, radioactive decay of these fission products also produces heat. Unless this heat is removed promptly, the (spent) fuel will melt down and release radioactive materials.
“That was what happened in Japan at the Fukushima nuclear plant. The initial earthquake cut off external power supplies. Even though the reactors were quickly shut down after that earthquake, the tsunami came soon after and knocked out the cooling system.
“There was then no way to cool their radioactive cores. That eventually led to the meltdowns and hydrogen explosions seen around the world on television sets as well as the release of radioactive materials.”
Headline photo of Zaporizhizhia nuclear power plant by Energoatom Facebook page.
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