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Exams > 2023 Q26 — EOP-TRIP-4 Natural Circulation / RCP Restart Priority

2023 Q26 — EOP-TRIP-4 Natural Circulation / RCP Restart Priority

⚠️ DRAFT
Q26 — EOP-TRIP-4 Natural Circulation / RCP Restart Priority W E09 EK3.06 (3.4)
Given:
• Unit 2 experienced a LOOP
• Crew is performing EOP-TRIP-4, Natural Circulation
• Power has been restored to 4KV Group Buses

How many RCPs are started and why?
A. One RCP; prevents two phase flow in the RCS.
B. Two RCPs; prevents two phase flow in the RCS.
C. Two RCPs; permits faster cooldown with less potential for upper head voiding.
D. One RCP; permits faster cooldown with less potential for upper head voiding.
▶ Show Answer & Explanation
✓ D. Correct. Per EOP-TRIP-4 bases Note N1-3: RCPs are started whenever possible. Forced convection permits faster cooldown with less potential for upper head voiding. RCP priority order: 23, 21+22 or 21+24, 21 (to provide normal PZR spray). Single pump operation is preferred in the loop providing best spray.
✗ A. Incorrect. "Prevents two phase flow" is the reason for stopping an RCP during a SBLOCA, not the reason for starting one during natural circulation cooldown. The correct reason is faster cooldown with less potential for upper head voiding.
✗ B. Incorrect. Two RCPs would only be started if 23 RCP is unavailable (to provide spray using 21+22 or 21+24). The "prevents two phase flow" reasoning is the basis for stopping RCPs during a SBLOCA, not for starting them during natural circulation.
✗ C. Incorrect. While the reason (faster cooldown, less head voiding) is correct, only one RCP is preferred. Two RCPs are only started if 23 is unavailable for spray. Note N1-1 allows two RCPs for better spray if 23 unavailable.
Ref: 2-EOP-TRIP-4 (R41) | Source: New | Cognitive: Fundamental/Memory

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