Describe logic fault tolerance in RPS/NANTeL.

• A. The system stops if any fault is detected.
• B. The system remains capable of performing its safety function in the presence of faults due to redundancy, diversity, and fault-detection mechanisms.
• C. Redundancy is avoided to simplify design.
• D. Fault-detection is disabled during operation.

Answer: (B)

Fault tolerance in RPS/NANTeL means the safety function remains available even when faults occur, thanks to redundancy, diversity, and fault-detection mechanisms. Redundancy provides multiple independent channels so one failure doesn’t disable the function. Diversity helps prevent common-cause failures by using different implementations for critical paths. Fault detection and self-checks continuously monitor health, detect anomalies, and trigger corrective actions or safe shutdowns before a dangerous condition develops. Together, these features ensure the system can still perform its safety role in the presence of faults. The other ideas describe stopping on any fault, removing redundancy, or turning off fault detection, which would undermine safety.