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Exams > 2018 Q18 — AFW Backleakage Testing and Consequences

2018 Q18 — AFW Backleakage Testing and Consequences

⚠️ DRAFT
Q18 — AFW Backleakage Testing and Consequences 061 AFW-A2.06 (2.7)
Given:
- Unit 2 is 100% Reactor Power and stable
- S2.OP-PT.AF-0002 (Auxiliary Feedwater Backleakage) Section 5.1 (Backleakage Monitoring and Determination) has just been completed
- Indications show there is backleakage on the 23 Auxiliary Feedwater line

In accordance with S2.OP-PT.AF-0002, which ONE of the following completes the statements below?

S2.OP-PT.AF-0002 was REQUIRED to be performed _(1)_ after an AFW Pump was initially shutdown in MODES 1-3.

Backleakage of feedwater into the AFW System can DISABLE the motor-driven AFW Pumps by causing _(2)_.
A. (1) IMMEDIATELY    (2) the pumps to rotate backward
B. (1) IMMEDIATELY    (2) vapor binding in the pumps
C. (1) between 30 to 60 minutes    (2) the pumps to rotate backward
D. (1) between 30 to 60 minutes    (2) vapor binding in the pumps
▶ Show Answer & Explanation
✓ D. Correct. For Part 1, IAW S2.OP-PT.AF-0002 P&L 3.1, "This procedure shall be performed 30 to 60 minutes after an Auxiliary Feedwater Pump is shutdown in Modes 1-3". For Part 2, IAW SOER 84-3 (and the AFW Lesson Plan), "backleakage of hot feedwater has disabled auxiliary feedwater (AFW) pumps due to steam binding."
✗ A. For Part 1, the candidate could incorrectly conclude that S2.OP-PT.AF-0002 is required to be performed immediately after an AFW Pump is shutdown in Modes 1-3. For Part 2, when a pump rotates backward and the pump is started, the duration of the starting current is extended because it takes longer to get up to speed. In some cases, this extended starting current can cause the breaker for the motor to open. RCPs are specifically designed with Anti-Reverse-Rotation Devices. The candidate could incorrectly conclude that backleakage of feedwater into the AFW System can DISABLE the motor-driven AFW Pumps by causing them to rotate backwards.
✗ B. For Part 1, the candidate could incorrectly conclude that S2.OP-PT.AF-0002 is required to be performed immediately after an AFW Pump is shutdown in Modes 1-3. Part 2 is correct.
✗ C. Part 1 is correct. For Part 2, when a pump rotates backward and the pump is started, the duration of the starting current is extended. RCPs are specifically designed with Anti-Reverse-Rotation Devices. The candidate could incorrectly conclude that backleakage causes the AFW pumps to rotate backwards.
Ref: NOS05AFW000-15 (Auxiliary Feedwater System) | LO: NOS05AFW000-15 — Discuss the procedural requirements associated with the AFW System, including major precaution and limitations; Given industry OE, review and outline a course of action to prevent recurrence | Source: New | Cognitive: Higher (Analysis)

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