Q31 — CVCS Auto Makeup / CV179 Failure
015 NIS-A3.05 (2.6)
Given:
• Unit 2 is in MODE 3 preparing to do a plant startup
At Time 07:00
• An AUTOMATIC RCS Makeup starts
At Time 07:01
• 125 VDC power to 2CV179 (PRIMARY WATER FLOW) has been lost
• The Primary Water Flow Deviation Alarm actuates
At Time 07:02
• 2CV185 (MAKEUP FLOWPATH) fails to AUTOMATICALLY close
Which ONE of the following completes the statements below?
The Primary Water Flow Deviation Alarm actuates when primary water flow is greater than a MINIMUM of ±_(1)_ gpm above the setpoint.
The Source Range NI Audible Count Rate indication is expected to _(2)_ as the makeup continues with 2CV179 in its failed position.
• Unit 2 is in MODE 3 preparing to do a plant startup
At Time 07:00
• An AUTOMATIC RCS Makeup starts
At Time 07:01
• 125 VDC power to 2CV179 (PRIMARY WATER FLOW) has been lost
• The Primary Water Flow Deviation Alarm actuates
At Time 07:02
• 2CV185 (MAKEUP FLOWPATH) fails to AUTOMATICALLY close
Which ONE of the following completes the statements below?
The Primary Water Flow Deviation Alarm actuates when primary water flow is greater than a MINIMUM of ±_(1)_ gpm above the setpoint.
The Source Range NI Audible Count Rate indication is expected to _(2)_ as the makeup continues with 2CV179 in its failed position.
A. _(1)_ 5.0 _(2)_ rise
B. _(1)_ 5.0 _(2)_ lower
C. _(1)_ 0.8 _(2)_ rise
D. _(1)_ 0.8 _(2)_ lower
▶ Show Answer & Explanation
✓ B. Correct. For Part 1 and IAW S2.OP-AR.ZZ-0012, the Primary Water Flow Deviation Alarm actuates when primary water flow is greater than a MINIMUM of ±5.0 gpm above the setpoint. For Part 2, 2CV179 fails closed. Consequently, actual boron flow into the boric acid blender will be higher than the predetermined setpoint for the auto makeup (based on current RCS Boron concentration). This will cause actual RCS boron concentration to rise since the boron concentration of auto makeup flow is higher than the setpoint for the existing RCS Boron concentration. An increase in actual RCS Boron concentration will insert negative reactivity which will cause the Source Range NI Audible Count Rate indication to lower.
✗ A. Part 1 is correct. For Part 2, the candidate could incorrectly conclude that 2CV179 fails open. With 2CV179 open during an automatic RCS makeup, actual RCS Boron Concentration will lower. Lowering actual RCS Concentration will add positive reactivity which will cause the Source Range NI Audible Count Rate indication to rise.
✗ C. For Part 1, the Boric Acid Flow Deviation actuates when boric acid flow is greater than a MINIMUM of ±0.8 gpm above the setpoint. Consequently, the candidate could incorrectly conclude that the Primary Water Flow Deviation Alarm actuates when primary water flow is greater than a MINIMUM of ±0.8 gpm above the setpoint. For Part 2, the candidate could incorrectly conclude that 2CV179 fails open.
✗ D. For Part 1, the Boric Acid Flow Deviation actuates when boric acid flow is greater than a MINIMUM of ±0.8 gpm above the setpoint. Part 2 is correct.
Ref: NOS05CVCS00-17 (Chemical and Volume Control System) | LO: NOS05CVCS00-17 Obj 11 — Given a CVCS failure, predict the effect on the RCS | Source: New | Cognitive: Higher
Connections
- Related systems: CVCS, Excore NIs
- Related procedures: S2.OP-AR.ZZ-0012 — Console Alarm Response
- Related exam: 2018 NRC Written Exam