Q46 — AFW Pressure Override / SG Levels
061000A3.03 (3.9)
Given:
• Unit 2 is at 100% Reactor Power.
• The Unit experiences a Reactor Trip coincident with a Loss of Off-Site Power.
• 21 AFW Pump PRESSURE OVERRIDE console bezel is illuminated and the associated AF21's remain closed.
With NO operator action, which ONE of the following indications will exist regarding SG level control?
• Unit 2 is at 100% Reactor Power.
• The Unit experiences a Reactor Trip coincident with a Loss of Off-Site Power.
• 21 AFW Pump PRESSURE OVERRIDE console bezel is illuminated and the associated AF21's remain closed.
With NO operator action, which ONE of the following indications will exist regarding SG level control?
A. AFW flow indication reading 0 gpm for 21 and 22 SGs.
B. AFW flow indication reading 0 gpm for 23 and 24 SGs.
C. 21 and 22 SG levels rising SLOWER than 23 and 24 SG levels.
D. 23 and 24 SG levels rising SLOWER than 21 and 22 SG levels.
▶ Show Answer & Explanation
✓ D. Correct. 21 AFW Pump's runout protection is preventing the pumps AF21 valves from opening (they remain closed due to < 1085 psig discharge pressure) and the 21AFW Pump feeds the 23 and 24 SGs combined with the fact that the 23 AFW Pump will also be running and feeding all 4 SGs. Therefore 23 and 24 SG levels will be rising slower due to less AFW flow.
✗ A. Incorrect. Plausible because 21 AFW Pump's runout protection is preventing the pumps AF21 valves from opening (they remain closed due to < 1085 psig discharge pressure) and the candidate may believe that 21AFW Pump feeds the 21 and 22 SGs. Incorrect because 21 AFW Pump feeds the 23 and 24 SGs and the 23 AFW Pump will also be running and feeding all 4 SGs. A 23 AFW Pump start will typically be demanded on a trip from 100% power, but will certainly be running due to the loss of off-site power (4KV Group Bus Undervoltage).
✗ B. Incorrect. Plausible because 21 AFW Pump's runout protection is preventing the pumps AF21 valves from opening (they remain closed due to < 1085 psig discharge pressure) and the 21 AFW Pump feeds 23 and 24 SGs. Incorrect because the 23 AFW Pump will also be running and feeding all 4 SGs. A 23 AFW Pump start will typically be demanded on a trip from 100% power, but will certainly be running due to the loss of off-site power (4KV Group Bus Undervoltage).
✗ C. Incorrect. Plausible because 21 AFW Pump's runout protection is preventing the pumps AF21 valves from opening (they remain closed due to < 1085 psig discharge pressure) and the candidate may believe that 21AFW Pump feeds the 21 and 22 SGs. Also plausible because the 23 AFW Pump will also be running and feeding all 4 SGs. Incorrect because 21 AFW Pump feeds the 23 and 24 SGs.
Ref: NOS05AFW000-15, Auxiliary Feedwater System | LO: ELOs 6 & 9 | Source: Modified, Salem 2014 NRC Exam, Q56 | Cognitive: Comprehension
Connections
- Related systems: AFW
- Related exam: 2020 NRC Written Exam