Q46 — AFW Pump Runout Protection Circuit Failure
061 K6.01 (2.5)
Given:
• Unit 2 was at 100% Power when a reactor trip occurred.
• BOTH Motor Driven AFW Pumps are running.
• 21 AFW Pump discharge pressure transmitter (2PA-3450) for the pump runout protection circuit fails to ZERO.
Based on the above condition, which ONE of the following completes both statements?
1. The 21 AFW Pump flow control valves (AF21s) will __(1)__.
2. To regain control of these valves from the control room, the operator will __(2)__ for 21 AFW Pump.
• Unit 2 was at 100% Power when a reactor trip occurred.
• BOTH Motor Driven AFW Pumps are running.
• 21 AFW Pump discharge pressure transmitter (2PA-3450) for the pump runout protection circuit fails to ZERO.
Based on the above condition, which ONE of the following completes both statements?
1. The 21 AFW Pump flow control valves (AF21s) will __(1)__.
2. To regain control of these valves from the control room, the operator will __(2)__ for 21 AFW Pump.
A. 1) open
2) select LOCAL MANUAL
2) select LOCAL MANUAL
B. 1) open
2) depress PRESS OVERRIDE DEFEAT
2) depress PRESS OVERRIDE DEFEAT
C. 1) close
2) depress PRESS OVERRIDE DEFEAT
2) depress PRESS OVERRIDE DEFEAT
D. 1) close
2) select LOCAL MANUAL
2) select LOCAL MANUAL
▶ Show Answer & Explanation
✓ C. Correct. The AFW discharge pressure transmitter inputs into the Pressure Override Protection circuit. The Pressure Override circuit will limit the position of the AF21s based on the discharge pressure of the AFW pump to prevent pump runout conditions. If discharge pressure is insufficient, then the circuit will throttle the AF21s closed. With the pressure transmitter failed to zero, the Pressure Override circuit associated with 21 AFW pump will close both the 23AF21 and 24AF21. In order for the operator to regain control of these valves, the operator is required to depress the PRESS OVERRIDE DEFEAT pushbutton which removes the runout protection circuit and allows the operator to control the AF21s.
✗ A. First part is incorrect. The 23AF21 and 24AF21 will fail closed when the pressure transmitter fails to zero. Second part is incorrect. The LOCAL MANUAL is indication only in the control room. When illuminated no auto start signals will start the AFW Pump. Plausible because the operator may believe that when the AFW pump is in LOCAL MANUAL that this will allow the operators in the control room to manually control the AF valves.
✗ B. First part is incorrect. The 23AF21 and 24AF21 will fail closed when the pressure transmitter fails to zero. Second part is correct. Plausible if the operator believes that the AF21s will go open when the pressure instrument fails to zero.
✗ D. First part is correct. Second part is incorrect. The LOCAL MANUAL is indication only in the control room. When illuminated no auto start signals will start the AFW Pump. Plausible because the operator may believe that when the AFW pump is in LOCAL MANUAL that this will allow the operators in the control room to manually control the AF valves.
Ref: NOS05AFW000-18 | LO: NOS05AFW000-18, Obj 17 — Given any of the following and appropriate control room reference material, evaluate and determine the effect on the Auxiliary Feedwater System: Failure of sensors and detectors | Source: Bank — Salem | Cognitive: Comprehension/Analysis
Connections
- Related systems: AFW
- Related exam: 2022 NRC Written Exam