Defense-in-depth policy states that a utility should:

Defense-in-depth policy states that a utility should:

• A. Design to prevent the occurrence of nuclear accidents; Assume that accidents will occur; Provide proven capability to meet the range of worst-case accidents.
• B. Design to maximize production; Assume accidents will occur; Provide surplus safety features.
• C. Design to prevent accidents; Assume accidents will not occur; Provide limited safety margins.
• D. Design to prevent accidents; Assume accidents will occur; Provide no plan for worst-case.

Answer: (A)

Defense-in-depth means building safety through multiple, independent layers so that a failure in one barrier doesn’t lead to an unsafe condition. The best approach for a utility is to design to prevent accidents, while also recognizing that accidents can occur and preparing to cope with them. That means providing proven capability to handle the range of worst-case accidents, so the plant can maintain safety even under severe events. This combination—preventing events, assuming failures can happen, and ensuring robust, tested responses to the most challenging scenarios—embodies the layered protection mindset. The other approaches miss this balance. Focusing solely on maximizing production ignores safety; assuming accidents won’t occur denies the reality that failures can happen; and offering no plan for worst-case fails to provide the necessary resilience backbone.

Defense-in-depth means building safety through multiple, independent layers so that a failure in one barrier doesn’t lead to an unsafe condition. The best approach for a utility is to design to prevent accidents, while also recognizing that accidents can occur and preparing to cope with them. That means providing proven capability to handle the range of worst-case accidents, so the plant can maintain safety even under severe events. This combination—preventing events, assuming failures can happen, and ensuring robust, tested responses to the most challenging scenarios—embodies the layered protection mindset.

The other approaches miss this balance. Focusing solely on maximizing production ignores safety; assuming accidents won’t occur denies the reality that failures can happen; and offering no plan for worst-case fails to provide the necessary resilience backbone.