Q30 — CVCS Charging/Letdown
004 K4.11 (3.1)
Given:
• Salem Unit 2 is at 100% Power.
• The 2CV4, Letdown Orifice Isolation Valve, is in service.
• The crew is transferring CVCS Letdown to the 2CV3, Letdown Orifice Isolation Valve, in accordance with S2.OP-SO.CVC-0001, Charging, Letdown, and Seal Injection.
• 2CV18, Letdown Pressure Control Valve, is in MANUAL.
• 2CC71, Letdown HX Temperature Control Valve, is in AUTO.
• The RO opens 2CV3.
Which ONE of the following describes how the 2CV18 will be adjusted and how the 2CC71 will respond to maintain letdown pressure and temperature within limits?
The 2CV18 will be...
• Salem Unit 2 is at 100% Power.
• The 2CV4, Letdown Orifice Isolation Valve, is in service.
• The crew is transferring CVCS Letdown to the 2CV3, Letdown Orifice Isolation Valve, in accordance with S2.OP-SO.CVC-0001, Charging, Letdown, and Seal Injection.
• 2CV18, Letdown Pressure Control Valve, is in MANUAL.
• 2CC71, Letdown HX Temperature Control Valve, is in AUTO.
• The RO opens 2CV3.
Which ONE of the following describes how the 2CV18 will be adjusted and how the 2CC71 will respond to maintain letdown pressure and temperature within limits?
The 2CV18 will be...
A. throttled CLOSE as pressure rises and the 2CC71 will modulate OPEN in response to higher temperature.
B. throttled OPEN as pressure rises and the 2CC71 will modulate OPEN in response to higher temperature.
C. throttled CLOSE as pressure lowers and the 2CC71 will modulate CLOSE in response to lower temperature.
D. throttled OPEN as pressure lowers and the 2CC71 will modulate CLOSE in response to lower temperature.
▶ Show Answer & Explanation
✓ B. Correct. When the 2CV3 (45 gpm orifice) is opened, along with 2CV4 already being open, letdown pressure and flow will rise. With the 2CV18 in Manual, the operator will be required to throttle open the 2CV18 to maintain letdown pressure around 300 psig. The 2CV6 letdown relief valve lifts at 600 psig. As letdown flow rises through the Letdown HX (Non-Regen HX), letdown temperature will rise resulting in the 2CC71 controller demand to rise and open the 2CC71 more to raise CCW flow through the Letdown HX. If letdown temperature reaches 136 °F, then the 2CV21 will automatically divert flow to the VCT to prevent damage to the Mixed Bed Resin.
✗ A. Incorrect. First part is incorrect. The 2CV18 will be throttled open as pressure rises. Second part is correct. Plausible because the operator may incorrectly determine how letdown pressure will respond when two orifice valves are open.
✗ C. Incorrect. First part is incorrect. The 2CV18 will be throttled open as pressure rises. Second part is incorrect. The 2CC71 will throttle open to lower letdown temperature. Plausible because the operator may incorrectly determine how letdown pressure will respond when two orifice valves are open.
✗ D. Incorrect. First part is incorrect. The 2CV18 will be throttled open as pressure rises. Second part is incorrect. The 2CC71 will throttle open to lower letdown temperature. Plausible because the operator may incorrectly determine how the 2CV18 should respond when letdown pressure rises.
Ref: NOS05CVCS00-18 | LO: NOS05CVCS00-18, Objective 4 | Source: Bank – Salem 2006 NRC RO31 | Cognitive: Comprehension/Analysis
Connections
- Related systems: CVCS, CCW
- Related procedures: S2.OP-SO.CVC-0001 — Charging Letdown and Seal Injection
- Related exam: 2022 NRC Written Exam