During natural circulation, what is true about RCS core exit thermocouple temperatures?

• A. They are stable or decreasing
• B. They are increasing
• C. They are unrelated
• D. They fluctuate wildly

Answer: (A)

Natural circulation moves coolant by buoyancy rather than a pump, so the flow rate is self-regulating and tends toward a steady value that balances heat generation with heat removal. The core exit thermocouple measures the coolant temperature as it leaves the core, and in this self-regulated loop that steady state means the exit temperature remains constant. If cooling improves or power drops, that constant value will trend downward rather than upward. It won’t rise steadily, and it won’t oscillate wildly under normal natural-circulation operation.