Q25 — LOCA Outside Containment from TRIP-3
WE02G2.4.45 (4.1)
Given
• Unit 2 has experienced a Small Break LOCA.
• The CRS has transitioned to 2-EOP-TRIP-3, SI Termination.
• 21 Charging Pump has been stopped and a normal charging alignment has been established.
• 21 and 22 Safety Injection Pumps have been stopped.
• 21 and 22 RHR Pumps have been stopped.
Prior to attempting to establish normal letdown, a number of overhead annunciators alarm and or reflash. The RO reports the following indications and OHA annunciators:
• A-6, RMS HI RAD OR TRBL, due to 2R41D, Plant Vent Effluent
• A-41, AUX ALM SYS PRINTER, due to 23 and 24 RHR Sump Pump starts.
• C-34 22 RHR SUMP OVRFLO
• D-40, SUBCLG CH A MARGIN LO, due to subcooling at 9 °F
• D-48, SUBCLG CH B MARGIN LO, due to subcooling at 9 °F
• E-36 PZR HTR OFF LVL LO, due to Pressurizer Level off scale low and unable to be recovered.
What procedure will be used to mitigate this event?
• Unit 2 has experienced a Small Break LOCA.
• The CRS has transitioned to 2-EOP-TRIP-3, SI Termination.
• 21 Charging Pump has been stopped and a normal charging alignment has been established.
• 21 and 22 Safety Injection Pumps have been stopped.
• 21 and 22 RHR Pumps have been stopped.
Prior to attempting to establish normal letdown, a number of overhead annunciators alarm and or reflash. The RO reports the following indications and OHA annunciators:
• A-6, RMS HI RAD OR TRBL, due to 2R41D, Plant Vent Effluent
• A-41, AUX ALM SYS PRINTER, due to 23 and 24 RHR Sump Pump starts.
• C-34 22 RHR SUMP OVRFLO
• D-40, SUBCLG CH A MARGIN LO, due to subcooling at 9 °F
• D-48, SUBCLG CH B MARGIN LO, due to subcooling at 9 °F
• E-36 PZR HTR OFF LVL LO, due to Pressurizer Level off scale low and unable to be recovered.
What procedure will be used to mitigate this event?
A. 2-EOP-LOCA-6, LOCA Outside Containment.
B. 2-EOP-LOCA-5, Loss of Emergency Recirculation.
C. 2-EOP-LOCA-2, Post LOCA Cooldown and Depressurization.
D. 2-EOP-TRIP-3, SI Termination.
▶ Show Answer & Explanation
✓ A. Correct. Based on the alarm indications given, the candidate will recognize that the CAS; “PZR Level cannot be maintained greater than 11%” is not met. They will “Start ECCS Pumps as necessary and GO TO EOP-LOCA-1.” However, other alarms indicate that there is a LOCA outside containment and EOP-LOCA-6 will be required to mitigate the event. A direct transition from TRIP-3 to LOCA-6 does not exist.
✗ B. Plausible because the candidate may believe that because alarms indicate a LOCA outside containment, that both RHR trains are now unavailable, therefore requiring a transition to EOP-LOCA-5, Loss of Emergency Recirculation to mitigate the event. Incorrect as a transition to EOP-LOCA-6 is required to mitigate the leak outside containment.
✗ C. Plausible because 2-EOP-TRIP-3, SI Termination, Steps 7 and 9 both direct transition to LOCA-2, Post LOCA Cooldown and Depressurization. Incorrect because the SI and RHR Pump steps are already completed, crew is to attempt letdown restoration next. The CAS is the applicable direction and subsequent transition from LOCA-1 to LOCA-6 for the indicated leak outside containment.
✗ D. Plausible because the candidate may believe that although there are indications of a leak outside containment, subcooling at 9°F is adequate and that TRIP-3, SI Termination should continue. They may also believe that since the RHR pumps are stopped, the leak in RHR is insignificant and that TRIP-3 will provide adequate mitigation and core protection.
Ref: 2-EOP-TRIP-3, SI Termination and Bases | LO: N/A | Source: New | Cognitive: Comprehension
Connections
- Related systems: ECCS, RHR, Radiation Monitoring
- Related EOPs: EOP-TRIP-3 — SI Termination, EOP-LOCA-1 — Loss of Reactor or Secondary Coolant, EOP-LOCA-6 — LOCA Outside Containment, EOP-LOCA-5 — Loss of Emergency Coolant Recirculation, EOP-LOCA-2 — Post LOCA Cooldown and Depressurization
- Related exam: 2020 NRC Written Exam