Q28 — RCP #2 Seal Design
003 K4.07 (3.2)
Which ONE of the following is a design feature of the Reactor Coolant Pump #2 seal?
A. Film riding seal with a design leak-off of 3 gph to the RCP standpipe; allows the RCP to operate indefinitely without restrictions upon a loss of the #1 seal.
B. Film riding seal with a design leak-off of 100 cc/hr to the RCP standpipe; serves as only an emergency backup upon a total loss of the #1 seal.
C. Face rubbing seal with a design leak-off of 3 gph to the RCP standpipe; serves as only an emergency backup upon a total loss of the #1 seal.
D. Face rubbing seal with a design leak-off of 100 cc/hr to the RCP standpipe; allows the RCP to operate indefinitely without restrictions upon a loss of the #1 seal.
▶ Show Answer & Explanation
✓ C. Correct. The #2 RCP seal is designed as a face rubbing seal. Normal leakage past the #2 seal is 3 gph and is directed to the #3 seal and the RCP standpipe. Upon a failure of the #1 seal, the #2 seal converts from face rubbing to film riding seal. In this condition, the #2 seal is NOT a controlled leakage seal. Not designed for high flow and high temperatures conditions when #1 seal fails. Acts as only an emergency backup to the loss of #1 seal. The RCP must be shutdown. RCP standpipe provides backpressure to limit #2 seal leakage and to maintain a certain pressure against #3 seal.
✗ A. Incorrect. First part is incorrect. #2 seal is not a film riding seal. Second part is incorrect. Plausible because the #1 seal is a film riding seal design.
✗ B. Incorrect. First part is incorrect. #2 seal is not a film riding seal. Second part is correct. Plausible because the #1 seal is a film riding seal design and the 100 cc/hr is for a #3 seal leakage.
✗ D. Incorrect. First part is incorrect. #2 seal leakage is 3 gph, 100 cc/hr is the design leakage for #3 seal. Second part is incorrect. RCP cannot operate indefinitely following loss of #1 seal, the RCP must be shutdown.
Ref: NOS05RCPUMP-16, RCP-1 simplified | LO: NOS05RCPUMP-16, Objective 4 | Source: Bank – Salem | Cognitive: Fundamental/Memory
Connections
- Related systems: RCPs, CVCS
- Related exam: 2022 NRC Written Exam