Q91 — Loss of All Charging Pumps
011A2.04 (3.7)
Given:
• Unit 2 is in MODE 1 at approximately 8 % Power. Power ascension in progress.
• 23 Charging Pump is cleared and tagged for maintenance.
• 22 Charging Pump is in service.
Subsequently;
• 2C 4KV Bus de-energizes due to a differential fault on the bus.
• The crew starts 21 Charging Pump, but it trips on overcurrent.
Complete the following statement concerning the procedural action required to be taken. The CRS will initiate ___________.
Note: S2.OP-AB.4KV-0003, Loss of 2C 4KV Vital Bus
S2.OP-AB.CVC-0001, Loss of Charging
2-EOP-TRIP-1, Reactor Trip or Safety Injection
• Unit 2 is in MODE 1 at approximately 8 % Power. Power ascension in progress.
• 23 Charging Pump is cleared and tagged for maintenance.
• 22 Charging Pump is in service.
Subsequently;
• 2C 4KV Bus de-energizes due to a differential fault on the bus.
• The crew starts 21 Charging Pump, but it trips on overcurrent.
Complete the following statement concerning the procedural action required to be taken. The CRS will initiate ___________.
Note: S2.OP-AB.4KV-0003, Loss of 2C 4KV Vital Bus
S2.OP-AB.CVC-0001, Loss of Charging
2-EOP-TRIP-1, Reactor Trip or Safety Injection
A. S2.OP-AB.4KV-0003 to re-energize the 2C bus from the 2C Emergency Diesel Generator, then start 22 Charging Pump.
B. S2.OP-AB.CVC-0001, to trip the Rx, confirm the Rx trip, initiate SI, and then enter 2-EOP-TRIP-1.
C. S2.OP-AB.4KV-0003, to trip the reactor and then enter 2-EOP-TRIP-1
D. S2.OP-AB.CVC-0001, and direct Unit 1 to start 13 Charging Pump using Unit 1 RWST.
▶ Show Answer & Explanation
✓ D. Correct. With no Unit 2 Charging Pumps available, step 3.50 of S2.OP-AB.CVC-0001(Q), Loss of Charging states; "COORDINATE with Unit 1 to place 13 Charging Pump in service using U/1 RWST."
✗ A. Plausible because the S2.OP-AB.4KV-0003(Q) does verify that the 2C Bus is energized from the 2C EDG and then starts and stops 2C Vital Bus Loads as necessary. Incorrect as the bus is not energized from the EDG due to the bus differential fault.
✗ B. Plausible because Tripping the Reactor and initiating Safety Injection is a possible action in S2.OP-AB.CVC-0001(Q) due to PZR Level not being able to be maintained. The candidate may believe that letdown is still in service and that PZR level is lowering in an uncontrolled manner.
✗ C. Plausible because Tripping the Reactor is a possible CAS action in S2.OP-AB.4KV-0003(Q). The candidate may believe that it is a conservative action due to the 2C bus being deenergized and no pressurizer level control.
Ref: S2.OP-AB.CVC-0001(Q), Loss of Charging and Bases. S2.OP-AB.4KV-0003(Q), Loss of 2C 4KV Vital Bus and Bases. | LO: N/A | Source: Modified Bank – ILOT 16-01 Audit Exam, Q53 | Cognitive: Comprehension
Connections
- Related systems: CVCS, 4KV
- Related procedures: AB.CVC-0001 — Loss of Charging, AB.4KV-0003 — Loss of 2C 4KV Bus
- Related EOPs: EOP-TRIP-1 — Reactor Trip or Safety Injection
- Related exam: 2020 NRC Written Exam