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Exams > 2023 Q3 — CVCS / CV71 Seal Backpressure Control

2023 Q3 — CVCS / CV71 Seal Backpressure Control

⚠️ DRAFT
Q3 — CVCS / CV71 Seal Backpressure Control APE 22 AA1.05 (3.3)
Given:
• Salem Unit 1 is experiencing a RCS leak inside containment.
• The crew is performing S1.OP-AB.RC-0001, Reactor Coolant System Leak.
• 11 charging pump is in service.
• The RO is attempting to stabilize PZR level by adjusting charging flow using the 1CV55, CHARGING FLOW CONTROL VALVE, and 1CV71, CHG HDR PCV.

Which of the following completes the below statement? When 1CV71 is throttled ...
A. open, seal injection rises and charging flow rises.
B. open, seal injection flow lowers and charging flow lowers.
C. closed, seal injection flow rises and charging flow lowers.
D. closed, seal injection lowers and charging flow rises.
▶ Show Answer & Explanation
✗ A. Incorrect. Throttling CV71 open would lower backpressure to the seal injection lines, resulting in lower seal injection flow and higher charging flow — the opposite of what this choice states.
✗ B. Incorrect. Throttling CV71 open would lower backpressure, but seal injection flow would lower and charging flow would rise, not both lower.
✓ C. Correct. When the 1CV71 is closed, then backpressure to the seal injection lines will rise resulting in rising RCP seal injection flows and allowing less charging flow to the non-regen HX, thereby lowering charging flow to the RCS. 1CV71 acts as a backpressure control valve that affects both charging and seal injection flows.
✗ D. Incorrect. Throttling CV71 closed raises backpressure, which raises seal injection flow — it does not lower it. Additionally, charging flow would lower, not rise.
Ref: S1.OP-AB.RC-0001 (R18), CVCS one-line dwg | LO: NOS05CVCS00-18, Obj 4 | Source: Bank - Byron 2017 NRC RO4 | Cognitive: Comprehension/Analysis

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