Aleksandre said:
World is on the edge of the nuclear disaster in Ukraine. Zaporojie. If it heppens noone can stop and avoid catastrophic results. What are the prognosis? Will it heppen or not. ? Are gods helping us??
:?
As a nuclear engineer, allow me to allay your worries.
To start out with, let's look at the two major disasters that have occurred with nuclear power plants. The first one, of course, is Chernobyl. There was a major fault with its design: its "positive void coefficient". In almost all reactors, water acts as both coolant and neutron moderator (the moderator is what slows down the neutrons released from fission so they can be absorbed into the fuel and start more fissions). This means when the coolant begins to boil, the pockets of steam that form (the voids) reduce the rate of neutron moderation and slow down the reaction, meaning the reactor can self-correct to a degree. However, in Chernobyl, water acted as the coolant, but the moderator was constructed of graphite, so this self-correction factor was nonexistent. Combined with grave mistakes by the operators, the reactor temperature began to soar, and this "positive void coefficient" began to dominate, causing the reaction to run away. This was further compounded by the fact that Soviet officials decided that the reactor was "inherently safe" and "is incapable of experiencing an accident," so they neglected to build proper containment facilities around the reactor itself.
The other one is Fukushima. This one also had design faults, though they were less serious. The biggest one was that the backup generators meant to keep the cooling and safety systems running were located in the plant's basement. The seawall around the plant was also insufficient. So when the tsunami hit, it overcame the seawall, flooded the basement, and shorted out the backup generators, so cooling to the reactors abruptly stopped. The reactors had been running at full power just before this incident, meaning there was a significant amount of heat still built up, and when this heat was unable to be removed, the reactors began melting down.
Now let's consider Zaporizhzhia. The reactors are a completely different design than Chernobyl, meaning a meltdown of that level is impossible. Also at present, all but one of the reactors are in cold shutdown, meaning they're "turned off" and do not require cooling. The remaining reactor is in hot shutdown, which still requires cooling, but there is not a great amount of heat built up, as in Fukushima. If Khakhovka does indeed dry up, bad things will happen, yes, but it'll be a Three Mile Island level incident at worst. In Three Mile Island, coolant was lost through a stuck valve and the reactor overheated and partially melted down, but nobody died and health effects were minimal.
Hopefully this helps.
