During natural circulation in a PWR, the RCS hot leg temperatures tend to be

During natural circulation in a PWR, the RCS hot leg temperatures tend to be

• A. Increasing
• B. Stable or decreasing
• C. Unchanging
• D. Oscillating

Answer: (B)

Buoyancy-driven flow in natural circulation moves heat through the loop without pumps: the hot water leaving the core is less dense and rises through the hot leg to the steam generators, then cooler water returns via the cold leg. The system seeks a balance where the heat produced in the core is removed by the steam generators. Once that balance is reached, the hot-leg temperature settles. If the plant is cooling, the hot-leg temperature drops; if power is steady, it stays roughly constant. So, during natural circulation the hot-leg temperatures tend to be stable or decreasing. They don’t keep rising, and persistent oscillations aren’t the normal outcome in steady natural circulation. Brief transients can occur, but the overall trend is toward equilibrium rather than growth.

Buoyancy-driven flow in natural circulation moves heat through the loop without pumps: the hot water leaving the core is less dense and rises through the hot leg to the steam generators, then cooler water returns via the cold leg. The system seeks a balance where the heat produced in the core is removed by the steam generators. Once that balance is reached, the hot-leg temperature settles. If the plant is cooling, the hot-leg temperature drops; if power is steady, it stays roughly constant. So, during natural circulation the hot-leg temperatures tend to be stable or decreasing. They don’t keep rising, and persistent oscillations aren’t the normal outcome in steady natural circulation. Brief transients can occur, but the overall trend is toward equilibrium rather than growth.