What design feature reduces the risk of control rod release mechanism failures?

• A. Redundancy in the control rod release mechanisms
• B. Increased reactor power
• C. Additional shielding
• D. Higher coolant flow

Answer: (A)

Redundancy in the control rod release mechanisms is the design feature that reduces the risk of a failure to release. Having multiple independent paths to release the rods means that if one path jams, loses power, or experiences a fault, the others can still operate and perform the SCRAM as commanded. This greatly lowers the overall probability that all release paths fail simultaneously, which is the essence of increasing reliability through defense-in-depth. The other options don’t directly improve the mechanical reliability of the release system; higher power, extra shielding, or increased coolant flow don’t reduce the chance of a release mechanism failure.