Which of the following is a critical parameter monitored during accident conditions for a BWR?

• A. Reactor Vessel Water Level
• B. Reactor Vessel Pressure
• C. Dry Well Temperature
• D. Suppression Chamber Water Level

Answer: (A)

In a boiling water reactor, keeping the core continuously submerged in coolant is essential for removing the heat produced, especially after an upset. The vessel water level directly indicates whether the core remains covered and thus being cooled. If the water level drops and the top of the fuel becomes exposed, rapid overheating can occur, fuel cladding can be damaged, and the situation can escalate toward core damage. Operators rely on the vessel water level as the primary signal to take actions such as adding makeup water or adjusting cooling paths to restore a safe level and maintain cooling.

While reactor vessel pressure, dry well temperature, and suppression chamber water level are important for overall safety and containment status, they do not provide as immediate and direct a read on the core cooling condition as the vessel water level does.