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Exams > 2023 Q41 — AFW TD Pump Response to Lowering SG Pressure

2023 Q41 — AFW TD Pump Response to Lowering SG Pressure

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Q41 — AFW TD Pump Response to Lowering SG Pressure T2G1 039 K3.03 (3.3)
Given:
• Salem Unit 2 reactor tripped and actuation of Main Steam Line Isolation occurred due to a steamline break
• ONLY the 23 AFW Turbine-Driven feedpump is running supplying all SGs
• ALL SG pressures are 900 psig and lowering rapidly

Which of the following completes the statement concerning the effect on the AFW system (assuming no operator action)?

When SG pressures lowers to 700 psig, 23 AFW turbine speed will (1) and feedflow will (2).
A. (1) lower (2) lower
B. (1) remain constant (2) rise
C. (1) remain constant (2) remain constant
D. (1) lower (2) rise
▶ Show Answer & Explanation
✓ B. Correct. 23 AFW Turbine Driven Pump is designed to operate with SG pressures at 100 psig. As SG pressures lower, the 23 AFW governor will throttle to maintain relative speed of the turbine constant. However, as SG pressure lowers, the D/P across the feedpump discharge and the SG will increase resulting in more AFW flow to the SGs.
✗ A. Incorrect. Plausible because the operator may believe that as SG pressure lowers so will the turbine speed and feedflow.
✗ C. Incorrect. Plausible because turbine speed will be maintain relatively constant and the operator may believe that feedflow will also remain constant. Incorrect in that feedflow will rise due to the lowering SG pressure.
✗ D. Incorrect. Plausible because feedflow will rise as SG pressure lowers.
Ref: NOS05AFW000-18 | Source: New | Cognitive: Comprehension/Analysis
K/A: 039 K3.03 — Knowledge of the effect that a loss or malfunction of the Main and Reheat Steam System will have on the following systems or system parameters: AFW system

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