EPRI - Core Protection| Engineering Systems Training| 76 QUESTIONS| WITH COMPLETE SOLUTIONS

Identify ways a core can fail correct answer: The primary cause of core failure is an inability to fully remove the heat created by the fuel due to the following: 1. A failure of the heat removal systems 2. An increase of heat created beyond the ability of the heat removal systems 3. The inability to transfer heat from the fuel What cooling capabilities could lead to core melt and a loss of core geometry correct answer: Loss of Cooling Capabilities • Loss of reactor coolant flow • Loss of coolant • Loss of feedwater flow • Loss of decay heat removal what excessive heat creation could lead to core melt and a loss of core geometry correct answer: • Failure of the reactor to trip when required (often referred to as anticipated transient without scram (ATWS)) [anticipated transient without scram (ATWS)- When the reactor protection system detects an unsafe condition and sends a signal to trip the reactor, but the reactor does not trip.] • Rod ejection (PWR) • Inadvertent deboration (PWR) [Deboration- Borated water is one method to control reactor reactivity. Deboration is the reduction of boron in the reactor coolant thus adding positive reactivity.] 'inability to transfer heat from the fuel' could lead to core melt and a loss of core geometry correct answer: • Loss of subcooling • Departure from nucleate boiling • Onset of transition boiling Identify grouped ways core can fail correct answer: loss of cooling capabilities excessive heat creation inability to transfer heat from the fuel what are the elements of the defense-in-depth philosophy correct answer: prevention of accidents