Q42 — EOP-LOCA-5 Table C CS Pumps Required
026000G2.1.25 (3.9)
Given:
- Unit 2 has experienced a design bases Large Break LOCA.
- The 2A Vital Bus is de-energized due to a Differential Protection Fault on the bus.
- The 22 RHR Pump has tripped.
At T+0:
- The crew enters 2-EOP-LOCA-5, Loss of Emergency Recirculation
- RO reports RWST Level is 20 feet.
At T+6 minutes:
- The crew is performing Step 9 of EOP-LOCA-5 to determine the required number of Containment Spray Pumps using Table C.
- RO reports Containment pressure is 18 psig.
At T+6 minutes, determine the relative RWST Level and the number of Containment Spray Pumps required in accordance with EOP-LOCA-5, Table C?
[REFERENCES PROVIDED]
- Unit 2 has experienced a design bases Large Break LOCA.
- The 2A Vital Bus is de-energized due to a Differential Protection Fault on the bus.
- The 22 RHR Pump has tripped.
At T+0:
- The crew enters 2-EOP-LOCA-5, Loss of Emergency Recirculation
- RO reports RWST Level is 20 feet.
At T+6 minutes:
- The crew is performing Step 9 of EOP-LOCA-5 to determine the required number of Containment Spray Pumps using Table C.
- RO reports Containment pressure is 18 psig.
At T+6 minutes, determine the relative RWST Level and the number of Containment Spray Pumps required in accordance with EOP-LOCA-5, Table C?
[REFERENCES PROVIDED]
A. RWST Level is < 15.24 ft., 0 Containment Spray Pumps are required.
B. RWST Level is > 15.24 ft., 0 Containment Spray Pumps are required.
C. RWST Level is > 15.24 ft., 1 Containment Spray Pump is required.
D. RWST Level is < 15.24 ft., 1 Containment Spray Pump is required.
▶ Show Answer & Explanation
✓ B. Correct. RWST level only lowers to 163900 gallons (>16') after 6 minutes based on "A" Bus loads being lost. (Uses 1100 gpm for both charging pumps, 650 gpm or 1 SI pump, and 2600 gpm for 1 CS pump) 4350 gpm x 6 minutes = 26100 gallons. 20' in RWST = 190000 gallons, therefore 190000 - 26100 = 163900 gallons (>16'). Using Table C of LOCA-5, RWST Level > 15.24', 18 psig containment pressure, and 4 CFCUs operating, then zero (0) CS pumps are required.
✗ A. Incorrect. Plausible because the operator may incorrectly determine how many ECCS & CS Pumps are operating and believe that after 6 minutes, RWST Level has decreased to less than 15.24'. If the candidate assumed the equivalent of "B" Bus loads were lost, then level would drop to 147700 gallons in 6 minutes and therefore be below 15.24'. The second part is correct.
✗ C. Incorrect. The first part is correct. Plausible because the candidate may believe that "A" bus powers 2 CFCUs and therefore determine that 1 CS pump is required.
✗ D. Incorrect. Plausible because the operator may incorrectly determine how many ECCS & CS Pumps are operating and believe that after 6 minutes, RWST Level has decreased to less than 15.24'. If the candidate assumed the equivalent of "B" Bus loads were lost, then level would drop to 147700 gallons in 6 minutes and therefore be below 15.24'. The second part is plausible, if the candidate incorrectly interprets Table C and/or doesn't understand CFCU power supplies.
Ref: 2-EOP-LOCA-5, Loss of Emergency Recirculation | LO: N/A | Source: New | Cognitive: Comprehension
Connections
- Related systems: ECCS, Containment Spray, CFCUs
- Related EOPs: EOP-LOCA-5 — Loss of Emergency Coolant Recirculation
- Related exam: 2020 NRC Written Exam