Okay, just finished HBO’s Chernobyl and have fallen down the deep deep rabbit hole of trying to understand how nuclear reactors work, why water is needed, what a meltdown is and what happened at Chernobyl.
I think I have a good handle on it, but one thing I’m still not sure on: what initially “turns on” a nuclear reactor?
I get that the uranium fuel is encased in the zirconium rods, and that when it’s up and running the splitting uranium releases neutrons that split even more uranium and so on.
And I get that uranium is unstable on its own and eventually decays.
What I don’t understand is what begins the initial fission process that produces the heat that steams the water that turns the turbine.
I mean, the whole point of submerging the rods in water (or encasing them in graphite) is to ensure that the reactor doesn’t overheat, but what starts the reaction that such submerging or encasement is necessary? When a the rods are being assembled, they aren’t already producing that kind of heat, are they? If they are, then how is construction of a reactor even possible?
Again, how does a nuclear reactor “turn on”, and, by extension, how is it “turned off”?
In: Chemistry
To start a fission reaction you need to get enough radioactive material, close enough together, so that it reaches critical mass. The radioactive materials shoot particles at each other which causes the other one to shoot particles back.
It could be as simple as having 2 buckets of radioactive material and moving the 2 buckets next to each other.
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