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Exams > 2018 Q17 — SGFP Suction Pressure Trip

2018 Q17 — SGFP Suction Pressure Trip

⚠️ DRAFT
Q17 — SGFP Suction Pressure Trip 059 MFW-A1.03 (2.7)
Given:
- Unit 2 is at 100% Reactor Power and stable

At time 09:00:00
- The suction pressure transmitter for the 22 SGFP FAILS to 200 psig

Which ONE of the following completes the statements below?

The 22 SGFP will TRIP _(1)_.
After 22 SGFP has tripped, Reactor Power will stabilize at approximately _(2)_ %.
A. (1) IMMEDIATELY (at 09:00:00)    (2) 50
B. (1) IMMEDIATELY (at 09:00:00)    (2) 66
C. (1) at 09:00:10 (after a 10 second delay)    (2) 50
D. (1) at 09:00:10 (after a 10 second delay)    (2) 66
▶ Show Answer & Explanation
✓ D. Correct. For Part 1, the SGFP will trip when suction pressure is less than 215 psig for 10 seconds. Consequently, given the question stem, 09:00:10 is the LATEST time that the 22 SGFP TRIPS. For Part 2, once 22 SGFP trips, a turbine runback to 66% will be generated. Since Reactor Power follows steam demand, Reactor Power will stabilize at approximately 66%.
✗ A. For Part 1, there is an instantaneous SGFP trip on low suction pressure (< 190 psig). The candidate could incorrectly conclude that the SGFP will trip instantaneously at 09:00:00. For Part 2, there are only two SGFPs. The candidate could incorrectly conclude that each SGFP provides 50% total flow and that a turbine runback will occur to 50%.
✗ B. For Part 1, there is an instantaneous SGFP trip on low suction pressure (< 190 psig). The candidate could incorrectly conclude that the SGFP will trip instantaneously at 09:00:00. Part 2 is correct.
✗ C. Part 1 is correct. For Part 2, there are only two SGFPs. The candidate could incorrectly conclude that each SGFP provides 50% total flow and that a turbine runback will occur to 50%.
Ref: NOS05CN&FDW-15 (Condensate and Feedwater System) | LO: NOS05CN&FDW-15 — Identify and describe the Control Room controls, indications, and alarms associated with the Condensate and Feedwater System | Source: Modified Bank | Cognitive: Higher (Analysis)

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