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Exams > 2020 Q27 — LOCA Voiding Indication

2020 Q27 — LOCA Voiding Indication

⚠️ DRAFT
Q27 — LOCA Voiding Indication WE03EK1.3 (3.5)
Given:
• Unit 2 has experienced a Small Break LOCA.
• An automatic Reactor Trip and SI have occurred.
• All RCPs have been stopped.
• The crew has transitioned to 2-EOP-LOCA-2, Post LOCA Cooldown and Depressurization.

In accordance with 2-EOP-LOCA-2, which ONE of the following operational indications describes how voiding can be identified in the RCS?
A. Rapidly rising Pressurizer Level.
B. Lowering Safety Injection Flow.
C. Rising RCS Pressure.
D. Rapidly lowering RCS Subcooling.
▶ Show Answer & Explanation
✓ A. Correct. Without RCPs running, the upper head remains relatively hot compared with the active regions of the RCS. Therefore steam formation during depressurization in the upper head will displace water into the Pressurizer, causing rapidly increasing Pressurizer level. (step 14 NOTE)
✗ B. Plausible because the RCS pressure is lowering, and SI flow is expected to increase during depressurization of the RCS but lowering SI flow would indicate saturation conditions exist which would promote void growth.
✗ C. Plausible because the RCS pressure is expected to be reduced during depressurization of the RCS, but increasing pressure would indicate saturation conditions exist to promote void growth.
✗ D. Plausible because subcooling is expected to be reduced during depressurization of the RCS and would indicate saturation conditions exist to promote void growth.
Ref: 2-EOP-LOCA-2, Post LOCA Cooldown and Depressurization and Bases | LO: N/A | Source: Bank — 2012 Harris NRC Exam / 2019 BV2 NRC Exam | Cognitive: Fundamental

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