Q87 — LOCA Sump Blockage / ECCS Flow
006G2.4.47 (4.2)
Given:
• Unit 2 was initially at 100% Power.
At T+0:
• A Large Break LOCA occurs.
• Automatic Rx Trip, Safety Injection, and Containment Spray have actuated.
• The CRS has transitioned to 2-EOP-LOCA-3, Transfer to Cold Leg Recirculation, from 2-EOP-TRIP-1, Reactor Trip or Safety Injection, based on RWST levels reaching 15.2 feet.
• RO reports following status of 2-EOP-LOCA-3 actions:
◦ Containment Sump Levels are > 62 %
◦ 21 and 22 SJ44 (Containment Sump Valves) are open.
◦ 21 and 22 RHR Pumps are running.
◦ 2SJ69 (Common Suction) is stroking closed.
At T+16 minutes:
• The 2SJ69 valve is closed and the following indications are reported by the Reactor Operator:
◦ 21 and 22 RHR Pump amps are oscillating.
◦ 21 and 22 RHR Pump flows are oscillating.
◦ 21 and 22 RHR Pump discharge pressures are oscillating.
Note: 2-EOP-APPX-7, Containment Sump Blockage Guideline
2-EOP-LOCA-5, Loss of Emergency Recirculation
Based on the above conditions, what procedure will the CRS enter NEXT to address this event and what is the MINIMUM ECCS Flow Rate required for decay heat removal at T+16 minutes?
[REFERENCES PROVIDED]
• Unit 2 was initially at 100% Power.
At T+0:
• A Large Break LOCA occurs.
• Automatic Rx Trip, Safety Injection, and Containment Spray have actuated.
• The CRS has transitioned to 2-EOP-LOCA-3, Transfer to Cold Leg Recirculation, from 2-EOP-TRIP-1, Reactor Trip or Safety Injection, based on RWST levels reaching 15.2 feet.
• RO reports following status of 2-EOP-LOCA-3 actions:
◦ Containment Sump Levels are > 62 %
◦ 21 and 22 SJ44 (Containment Sump Valves) are open.
◦ 21 and 22 RHR Pumps are running.
◦ 2SJ69 (Common Suction) is stroking closed.
At T+16 minutes:
• The 2SJ69 valve is closed and the following indications are reported by the Reactor Operator:
◦ 21 and 22 RHR Pump amps are oscillating.
◦ 21 and 22 RHR Pump flows are oscillating.
◦ 21 and 22 RHR Pump discharge pressures are oscillating.
Note: 2-EOP-APPX-7, Containment Sump Blockage Guideline
2-EOP-LOCA-5, Loss of Emergency Recirculation
Based on the above conditions, what procedure will the CRS enter NEXT to address this event and what is the MINIMUM ECCS Flow Rate required for decay heat removal at T+16 minutes?
[REFERENCES PROVIDED]
A. 2-EOP-APPX-7; 500 gpm.
B. 2-EOP-LOCA-5; 500 gpm.
C. 2-EOP-APPX-7; 550 gpm.
D. 2-EOP-LOCA-5; 550 gpm.
▶ Show Answer & Explanation
✓ C. Correct. The correct transition is to EOP-APPX-7, Containment Sump Blockage Guideline because of the cavitation indications which would result from sump blockage. When approximately 16 minutes time elapsed is read from Figure A, the minimum ECCS Flow would be approximately 550 gpm.
✗ A. Incorrect. The first part is correct. The second part is plausible because the candidate may incorrectly read the log scale for time on the provided Figure A.
✗ B. Incorrect. The first part is plausible because EOP-LOCA-5 would be the transition if the loss of recirculation was due to only mechanical or electrical component failures resulting in the inability to establish cold leg recirculation. The second part is plausible because the candidate may incorrectly read the log scale for time on the provided Figure A.
✗ D. Incorrect. The first part is plausible because EOP-LOCA-5 would be the transition if the loss of recirculation was due to only mechanical or electrical component failures resulting in the inability to establish cold leg recirculation. The second part is correct.
Ref: 2-EOP-LOCA-3 and Bases; 2-EOP-LOCA-5 and Bases; 2-EOP-APPX-7 and Bases | LO: N/A | Source: New | Cognitive: Comprehension
Connections
- Related systems: ECCS, RHR
- Related EOPs: EOP-LOCA-3 — Transfer to Cold Leg Recirculation, EOP-LOCA-5 — Loss of Emergency Coolant Recirculation, EOP-APPX-7 — Containment Sump Blockage
- Related exam: 2020 NRC Written Exam