Which of the following is a critical parameter monitored during accident conditions in a PWR?

• A. RCS Pressure
• B. Main Steam Line Temperature
• C. Turbine Bypass Flow
• D. PZR Water Level

Answer: (A)

During accident conditions in a PWR, the most critical parameter is the reactor coolant system pressure because it directly reflects the state of the primary coolant loop and governs how cooling can be provided. The core cooling strategy hinges on whether the system is maintaining high-pressure conditions that allow high-pressure injection or if depressurization is needed to enable low-pressure injection. Keeping the RCS pressure within appropriate bounds ensures the coolant remains in the right phase and circulation continues to remove heat from the core, preventing fuel damage.

Other parameters relate to steam side conditions or secondary aspects of the plant and do not drive the immediate cooling strategy as directly as system pressure does. For example, main steam line temperature tracks steam conditions, turbine bypass flow concerns the turbine loop, and while pressurizer water level is important, it changes as a result of injection and depressurization actions rather than signaling the core cooling mode on its own.