I don’t understand a #####ing word you said.
how embarrassing.
This was how it was explained to us in school:
Radioactivity is the quality of giving off neutrons. A nuclear chain reaction starts when radioactive material is sufficiently concentrated to create a storm of neutrons which split atoms which in turn give off neutrons to split other atoms.
An uncontrolled chain reaction can result in an atomic explosion. A controlled chain reaction gives off usable heat; the controlling element is carbon which is in the form of bundled rods inside the nuclear reactor. Carbon absorbs neutrons like a sponge; the control rods are inserted or withdrawn within the reactor chamber to regulate the amount of heat given off.
Nuclear heat operates boilers which drive steam turbines. There is also a cooling system which if I recall is a backup or fail-safe to the reactor control rods. If that should fail, the emergency response is to ram the control rods all the way into the reaction chamber (scramming) which shuts down the chain reaction process. Meltdown averted.
Scramming a reactor always makes news because of the Three Mile Island incident of 1979.
I’m no nuclear scientist. Does this help?