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Exams > 2019 Q54 — VCT LT-112 Failure and Loss of RCS Makeup

2019 Q54 — VCT LT-112 Failure and Loss of RCS Makeup

⚠️ DRAFT
Q54 — VCT LT-112 Failure and Loss of RCS Makeup APE: 022 Loss of Reactor Coolant Makeup-AA1.08 (3.4)
Given:
• Unit 2 is at 100% Reactor Power and stable

At time 09:00
• 2LT-112 (VCT Level Transmitter) fails to 50%

At time 09:10
• An RCS leak of 15 gpm is observed

Which ONE of the following completes the statements below?

ACTUAL VCT level will lower ___
A. and CYCLE between 14% and 24% due to the operation of the AUTOMATIC RCS Make up controls
B. and CYCLE between 11% and 24% due to the operation of the AUTOMATIC RCS Make up controls
C. and STABILIZE at approximately 3.57% as the Charging Pump suction AUTOMATICALLY swaps to the RWST
D. to BELOW 3.57% with the running Charging Pump eventually losing suction
▶ Show Answer & Explanation
✓ D. Correct. With 2LT-112 failed at 50% and an observed 15 gpm RCS leak, the running charging pump will eventually lose suction as actual VCT lowers below 3.57%. There are two level transmitters on the VCT (LT-112 and LT-114). LT-112 controls the automatic make-up controls (starts at 14% and stops at 24%). With LT-112 failed at 50%, no automatic RCS Make-up is possible. Additionally, the Charging Pump suction AUTOMATICALLY swaps to the RWST only when BOTH LT-112 and LT-114 read 3.57%.
✗ A. Incorrect but plausible. This would be the correct answer if 2LT-114 had failed to 50% with an observed 15 gpm RCS leak.
✗ B. Incorrect but plausible. This would be the correct answer if 2LT-114 had failed to 50% with an observed 15 gpm RCS leak and the candidate had incorrectly concluded that the AUTOMATIC Make-up started at 11% VCT Level (the VCT low level alarm setpoint).
✗ C. Incorrect but plausible. This would be the correct answer if the candidate incorrectly concluded that the Charging Pump suction AUTOMATICALLY swaps to the RWST when 2LT-112 OR 2LT-114 read 3.57%.
Ref: NOS05CVCS00-17 (CHEMICAL AND VOLUME CONTROL SYSTEM) | LO: NOS05CVCS00-17 | Source: New | Cognitive: Higher

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