Single correct option
In a nuclear reactor, the control rods used to absorb the excess neutrons are made of
- A. boron or cadmium
- B. graphite or heavy water
- C. uranium-238
- D. lead or steel
Show answer and solution
Answer: (A) boron or cadmium
Boron and cadmium absorb neutrons strongly, so lowering the rods slows the chain reaction and raising them speeds it. Graphite and heavy water are moderators that slow down the neutrons without absorbing many of them. Uranium-238 is a fertile material, and lead is used for shielding.
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