Q5 — CCW Thermal Barrier / RCP Impact
APE15 AK2.08 (2.6)
Given:
• Unit 1 is in MODE 3 at normal operating temperature and pressure.
• While performing troubleshooting activities, the 1CC190, CCW Thermal Barrier Isolation Valve, closes.
Which ONE of the following completes the statement concerning the impact this failure will have on the RCPs?
Thermal Barrier CCW return flow has been lost from ...
• Unit 1 is in MODE 3 at normal operating temperature and pressure.
• While performing troubleshooting activities, the 1CC190, CCW Thermal Barrier Isolation Valve, closes.
Which ONE of the following completes the statement concerning the impact this failure will have on the RCPs?
Thermal Barrier CCW return flow has been lost from ...
A. ALL RCPs. RCP operation may continue.
B. ONLY 1 RCP. RCP operation may continue.
C. ALL RCPs. All RCPs must be stopped within 2 minutes due to loss of cooling.
D. ONLY 1 RCP. The affected RCP must be stopped within 2 minutes due to loss of cooling
▶ Show Answer & Explanation
✓ A. Correct. The 1CC190 is on the common CCW return line and will isolate the CCW return from all RCP Thermal Barriers. So long as charging flow is supplied to the RCP seals, the RCPs can continue running. The stem did not indicate any issues with charging flow, therefore RCP operation may continue.
✗ B. Incorrect. Plausible because each RCP has individual isolation valves (CC130s) on the CCW return line. Second part is plausible because all reactor coolant loops (RCPs) are required to be in service only during Modes 1 and 2 per TS 3.4.1.1, so it's plausible to believe that you can operate with one RCP out of service in Mode 3.
✗ C. Incorrect. The 1CC190 is on the common CCW return line and will isolate the CCW return from all RCP Thermal Barriers. Second part is plausible because this is an action in S1.OP-AB.RCP-0001 when there is a loss of CCW to the Thermal Barrier and loss of charging for 2 minutes. The applicant may incorrectly interpret this action and believe that with a loss of all CCW to the Thermal Barriers that the RCP must be tripped in 2 minutes.
✗ D. Incorrect. Plausible because each RCP has individual isolation valves (CC130s) on the CCW return line. Second part is plausible because this is an action in S1.OP-AB.RCP-0001 when there is a loss of CCW to the Thermal Barrier and loss of charging for 2 minutes. The applicant may incorrectly interpret this action and believe that with a loss of all CCW to the Thermal Barriers that the RCP must be tripped in 2 minutes.
Ref: S1.OP-AB.RCP-0001 (R26), CCW-2 simplified | LO: NOS05ABRCP0, Obj 3 — Describe, in general terms, the actions taken in S2.OP-AB.RCP-0001 and the bases for the actions in accordance with the Technical Bases Document | Source: Bank — DC Cook 2018 NRC RO4 | Cognitive: Fundamental/Memory
Connections
- Related systems: CCW, RCPs
- Related procedures: AB.RCP-0001 — RCP Abnormality
- Related exam: 2022 NRC Written Exam