Q54 — CVCS Letdown Orifice Phase A Isolation
103 A3.01 (3.9)
Given:
• A reactor trip and Safety Injection are actuated
• PZR level is 25% and stable.
• 1CV2 and 1CV277, Letdown Isolation Valves, are open.
• 1CV3 and 1CV5, Letdown Orifice Isolation Valves, were closed prior to the reactor trip.
• 1CV4, Letdown Orifice Isolation Valve, is open.
• 1CV7, Letdown Containment Isolation Valve, is open.
Which ONE of the following completes the statement?
The 1CV4...
• A reactor trip and Safety Injection are actuated
• PZR level is 25% and stable.
• 1CV2 and 1CV277, Letdown Isolation Valves, are open.
• 1CV3 and 1CV5, Letdown Orifice Isolation Valves, were closed prior to the reactor trip.
• 1CV4, Letdown Orifice Isolation Valve, is open.
• 1CV7, Letdown Containment Isolation Valve, is open.
Which ONE of the following completes the statement?
The 1CV4...
A. is responding as designed since it is interlocked with the closure of the 1CV2 or 1CV277.
B. is responding as designed since it is interlocked with the closure of the 1CV7.
C. has failed open since it receives a signal directly from Safety Injection.
D. has failed open since it receives a signal directly from Phase A.
▶ Show Answer & Explanation
✓ D. Correct. The 1CV4 closes on the following signals/interlocks; Phase A, 1CV2 or 1CV277 closing, PZR level <17%, the trip all charging pumps, or manual actuation (Phase A) from the safeguards bezel in the control room. The stem states that a SI has actuated which results in the actuation of Phase A signal to isolate containment penetrations and valves. The 1CV4 closes directly from a Phase A signal, which is actuated from the SI signal. Since the 1CV4 is open, this means that the 1CV4 failed to close.
✗ A. Incorrect. Plausible because the 1CV2 or 1CV277 closing will close the orifice isolation valves. The 1CV2 and 1CV277 close only on PZR low level <17%. The applicant may confuse this interlock and believe that since the 1CV2 and 1CV277 are still open in the stem that this is the reason for the 1CV4 not closing as designed by the interlock.
✗ B. Incorrect. Plausible because the 1CV7 does close on Phase A signal and is interlocked with the 1CC71 valve to close isolating CCW to the letdown HX. The applicant may confuse 1CV7 is interlocked with the closure of the letdown orifice valves 1CV3, 4, and 5. Since the 1CV7 didn't close, then its plausible to believe that's the reason for the 1CV4 not closing as designed.
✗ C. Incorrect. Per logic drawing 221057, plausible because the applicant may confuse that a SI signal directly actuates the letdown isolation valves (i.e., 1CV4). The SI signal does directly actuate some valves, for example the 1CV68 and 1CV69 valves receive a closure signal directly from SI only and not Phase A. The Phase A is actuated from either an Auto or Manual SI signal or manual actuation from the safeguards bezel in the control room.
Ref: Simplified dwg CV-2, 221057 (R23) | LO: NOS05CVCS00-18, Obj 4 — Describe the function and how their normal and abnormal operations affects the Chemical and Volume Control System: containment orifice isolation valves CV3, CV4, CV5 | Source: Modified Bank - Byron 2017 NRC RO30 | Cognitive: Comprehension/Analysis
Connections
- Related systems: CVCS, Containment
- Related exam: 2022 NRC Written Exam