Control rods in nuclear reactor
Rods of neutron-absorbing material (typically cadmium or boron) inserted into a reactor core to control the multiplication factor k. By absorbing neutrons, control rods reduce k toward 1, maintaining steady-state power output.
Real World
During the Three Mile Island incident in 1979, control rods were successfully inserted within seconds, shutting down the fission chain reaction — though decay heat from radioactive products still caused partial core meltdown.
Exam Focus
Distinguish control rods (adjust k) from moderator (slow neutrons) — confusing these two functions loses marks on 'describe reactor operation' questions.
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