Q38 — CFCU Response to Inadvertent SI / SEC Mode 1
022 A2.07 (4.0)
Given:
• Salem Unit 2 is at 100% power
• 21, 22, 23 and 24 CFCUs are running in HIGH speed with 25 CFCU in standby
• An inadvertent SI actuation occurs
Which of the following completes both statements?
1. Following SI actuation, all CFCUs will start in LOW speed (1).
2. To restore CFCUs to HIGH speed operation, (2) must be RESET.
• Salem Unit 2 is at 100% power
• 21, 22, 23 and 24 CFCUs are running in HIGH speed with 25 CFCU in standby
• An inadvertent SI actuation occurs
Which of the following completes both statements?
1. Following SI actuation, all CFCUs will start in LOW speed (1).
2. To restore CFCUs to HIGH speed operation, (2) must be RESET.
A. After 20 seconds; reset SI only.
B. After 20 seconds; reset SI and SECs.
C. Immediately; reset SI and SECs.
D. Immediately; reset SI only.
▶ Show Answer & Explanation
✓ B. Correct. SEC Mode 1 (SI only): running CFCUs are tripped, then all five start 20 seconds later in low speed. The 20-second time delay allows for motor coastdown before restart. To regain manual control for high speed operation: must reset BOTH trains of SI AND reset all SECs. EOP-TRIP-3 step 1 accomplishes this.
✗ A. Incorrect. The 20-second delay is correct, but resetting SI alone is not sufficient. Both SI trains AND all SECs must be reset to regain manual control of the CFCUs for high speed operation.
✗ C. Incorrect. CFCUs do not restart immediately. The 20-second time delay is required to allow motor coastdown before restarting in low speed. The SI and SEC reset requirement is correct.
✗ D. Incorrect. CFCUs do not restart immediately (20-second delay required for coastdown), and resetting SI only is not sufficient — all SECs must also be reset to regain manual control.
Ref: NOS05SEC000-09, 2-EOP-TRIP-3 (R41) | Source: Modified - Braidwood 2016 NRC RO20 | Cognitive: Comprehension/Analysis
Connections
- Related systems: CFCUs, RPS/SSPS
- Related procedures: EOP-TRIP-3 — SI Termination
- Related exam: 2023 NRC Written Exam