Q4 — RHR Solid Plant Pressure Response
005 RHRS-K5.05 (2.7)
Given:
- Unit 2 is in MODE 5 with solid plant pressure control
- BOTH Trains of RHR are in service providing RCS cooling
- 2CV8 (RHR Purification Flow Control Valve) is throttled open
- RCS pressure is being controlled at 300 psig with 2CV18 (Low Pressure Letdown Control Valve) in MANUAL
At time 19:00
- The NCO manually adjusts the following RHR valves:
- 22RH18 (RHR HX Outlet Valve) is throttled MORE CLOSED
- 2RH20 (RHR HX Bypass Valve) is throttled MORE OPEN
- 21/22SJ49 flow remains constant
Which ONE of the following completes the statements below?
As RCS temperature responds to the RHR system adjustments, RCS pressure will INITIALLY _(1)_.
The NCO will then manually throttle 2CV18 MORE _(2)_ to restore RCS pressure to 300 psig.
- Unit 2 is in MODE 5 with solid plant pressure control
- BOTH Trains of RHR are in service providing RCS cooling
- 2CV8 (RHR Purification Flow Control Valve) is throttled open
- RCS pressure is being controlled at 300 psig with 2CV18 (Low Pressure Letdown Control Valve) in MANUAL
At time 19:00
- The NCO manually adjusts the following RHR valves:
- 22RH18 (RHR HX Outlet Valve) is throttled MORE CLOSED
- 2RH20 (RHR HX Bypass Valve) is throttled MORE OPEN
- 21/22SJ49 flow remains constant
Which ONE of the following completes the statements below?
As RCS temperature responds to the RHR system adjustments, RCS pressure will INITIALLY _(1)_.
The NCO will then manually throttle 2CV18 MORE _(2)_ to restore RCS pressure to 300 psig.
A. (1) rise (2) CLOSED
B. (1) rise (2) OPEN
C. (1) lower (2) CLOSED
D. (1) lower (2) OPEN
▶ Show Answer & Explanation
✓ B. Correct. For Part 1 and since flow through 22 RHR HX is lowered (when 22RH18 is throttled more closed), RCS temperature will rise. With the plant water solid, this will cause RCS pressure to initially rise (since water is incompressible). For Part 2, solid plant pressure control is maintained by holding charging flow constant and adjusting letdown flow. To lower RCS pressure during solid plant operations, letdown flow must be raised (with a constant charging flow). Consequently, the operator must throttle 2CV18 more open to restore RCS pressure to 300 psig.
✗ A. Incorrect but plausible. Part 1 is correct. For Part 2, the candidate could have a misunderstanding how solid plant pressure control works and incorrectly conclude that throttle 2CV-18 more closed will restore RCS pressure to 300 psig.
✗ C. Incorrect but plausible. For Part 1, the candidate could incorrectly conclude that RCS temperature will initially lower (which will also cause RCS pressure to lower) based on the adjustment to the RHR System. Part 2 would be correct if RCS pressure had actually lowered.
✗ D. Incorrect but plausible. For Part 1, the candidate could incorrectly conclude that RCS temperature will initially lower (which will also cause RCS pressure to lower) based on the adjustment to the RHR System. For Part 2, the candidate could have a misunderstanding how solid plant pressure control works and incorrectly conclude that throttle 2CV-18 more open will restore RCS pressure to 300 psig (when RCS pressure was too low).
Ref: NOS05RHR000-16, NOS05CVCS00-17 | LO: NOS05CVCS00-17 | Source: New | Cognitive: Higher
Connections
- Related systems: RHR, CVCS
- Related exam: 2019 NRC Written Exam