How does a RBMK reactor explode?
In: Chemistry
In very simple terms – the reactor works because radioactive particles break apart and release radiation energy as they do so. This is used to heat water, to create steam, which then drives turbines (big fans) than generate electricity. The reaction also make lots of tiny particles called neutrons go bouncing around. These neutrons can bump into other radioactive particles making them break up.
Without anything to ‘put the breaks on’ this, it will lead get out of control, where more particles break up, sending more neutrons bouncing around, which makes even more particles break up.
In an RBMK reactor, one of the things that keeps the brakes on is the water that is being heated up by the reaction, as it absorbs the neutrons bouncing around. But if the water is boiling, the bubbles in the water make it less dense and so it absorbs fewer neutrons. That means the higher the rate of reaction, the more the water boils, the fewer neutrons get absorbed, so the reaction gets even stronger and so on. There are other ways to calm down the reaction, including rods made out of Boron that also absorb neutrons, these rods can be lowered into the reactor to slow it down, or raised up to increase reaction.
Essentially, an explosion happens if the various effects that are calming the reaction down are weaker than the effects that are ramping it up.
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