EPRI Core Protection NANTeL Practice Test

The scenario being tested is the most demanding LOCA case used for a PWR design basis. In licensing analyses, the design-basis LOCA for a pressurized-water reactor is a double-ended rupture of the reactor coolant piping with simultaneous loss of off-site power. This combination creates the largest loss of coolant inventory plus no external electrical power, so the plant must rely on on-site diesels, batteries, and the Emergency Core Cooling System to keep the core cooled and decay heat removed while containment handles the pressures and heat loads. It sets the bounding conditions for safety systems, ensuring they can perform even under the worst credible combination of a large break and power loss. The other options do not represent that limiting scenario: they either lack the full double-ended break or the simultaneous loss of off-site power, or they describe a different kind of event altogether.