Q74 — Condensate Depression Effects on Efficiency and Cavitation
T4 193004 K1.11 (2.5)
Given:
- Salem Unit 2 is operating at 80% power.
- All Circulators are in service.
Which of the following completes the statement?
If condensate depression decreases from 5 degrees F to 2 degrees F, the steam cycle thermal efficiency will (1) and the condensate pumps will operate (2) cavitation.
- Salem Unit 2 is operating at 80% power.
- All Circulators are in service.
Which of the following completes the statement?
If condensate depression decreases from 5 degrees F to 2 degrees F, the steam cycle thermal efficiency will (1) and the condensate pumps will operate (2) cavitation.
A. (1) lower (2) closer to
B. (1) lower (2) farther from
C. (1) rise (2) closer to
D. (1) rise (2) farther from
▶ Show Answer & Explanation
✓ C. Correct. Changing the condensate depression from 5 degrees F to 2 degrees F will decrease the condensate depression. If condensate depression decreases, then the condensate will be closer to saturation temperature. This produces less NPSH at the suction of the condensate pump, raising the probability of cavitation. However, because the condensate is now at a higher temperature, the steam generators must add less sensible heat to the feedwater to reach saturated conditions, increasing plant efficiency.
✗ A. First part is incorrect. Plausible because the operator may believe with a lower condensate depression, the feedwater temperature will lower causing a rise in reactor power, and therefore, increase in plant efficiency. Second part is correct.
✗ B. First part is incorrect. Plausible because the operator may believe with a lower condensate depression, the feedwater temperature will lower causing a rise in reactor power, and therefore, increase in plant efficiency. Second part is incorrect. Plausible because the operator may incorrectly recall how a lower condensate depression will affect suction pressure at the condensate pump and the likelihood of pump cavitation. Incorrect in that a lower condensate depression will increase the likelihood of pump cavitation.
✗ D. First Part is correct. Second Part is incorrect. Plausible because the operator may incorrectly recall how a lower condensate depression will affect suction pressure at the condensate pump and the likelihood of pump cavitation. Incorrect in that a lower condensate depression will increase the likelihood of pump cavitation.
Ref: INPO GFES Thermodynamic Process (R3) | LO: NOS05THRMPR-03, ELO 2.2 Condenser Design and Characteristics | Source: Bank - INPO GFES P2576 | Cognitive: Comprehension/Analysis
Connections
- Related systems: Feed & Condensate, Main Turbine
- Related exam: 2023 NRC Written Exam