Q65 — LOCA-5 RCS Depressurization and Upper Head Voiding
W/E11 Loss of Emergency Coolant Recirculation-EK1.1 (3.7)
Given:
• The crew is preparing to perform the RCS Depressurization To Minimize Subcooling Steps of 1-EOP-LOCA-5 (Loss Of Emergency Recirculation)
• ALL RCPs are stopped
• PZR Level is 10%
• RCS Subcooling is 35 °F
At time 16:15:00
• The RCS depressurization has started
At time 16:15:30 (30 seconds later)
• PZR Level is 45% and rising
• RCS Subcooling is 25 °F
In accordance with 1-EOP-LOCA-5, which ONE of the following completes the statements below?
At 16:15:00, the crew used _(1)_ to depressurize the RCS.
At 16:15:30, there _(2)_ indications that voiding is occurring in the upper head region.
• The crew is preparing to perform the RCS Depressurization To Minimize Subcooling Steps of 1-EOP-LOCA-5 (Loss Of Emergency Recirculation)
• ALL RCPs are stopped
• PZR Level is 10%
• RCS Subcooling is 35 °F
At time 16:15:00
• The RCS depressurization has started
At time 16:15:30 (30 seconds later)
• PZR Level is 45% and rising
• RCS Subcooling is 25 °F
In accordance with 1-EOP-LOCA-5, which ONE of the following completes the statements below?
At 16:15:00, the crew used _(1)_ to depressurize the RCS.
At 16:15:30, there _(2)_ indications that voiding is occurring in the upper head region.
| (1) | (2) |
A. AUX SPRAY / are NOT
B. AUX SPRAY / are
C. a PZR PORV / are NOT
D. a PZR PORV / are
▶ Show Answer & Explanation
✓ D. Correct. For Part 1, IAW 1-EOP-LOCA-5 Step 24, with normal spray not available, the crew will depressurize the RCS using a PZR PORV. For Part 2, IAW 1-EOP-LOCA-5 Step 24, voiding in the upper head region will result in rapidly rising PZR Level. Since PZR Level has risen 35% in 30 seconds, there are indications that voiding is occurring in the upper head region.
✗ A. Incorrect but plausible. For Part 1, depressurizing the RCS using a PZR PORV will result in a loss of RCS inventory. The candidate may conclude that losing RCS inventory is not desirable and incorrectly conclude that the RCS will be depressurized using AUX SPRAY. For Part 2, the candidate may not understand the expected indications associated with voiding in the upper head region. Consequently, the candidate could incorrectly conclude that there are not indications that voiding is occurring in the upper head region.
✗ B. Incorrect but plausible. For Part 1, depressurizing the RCS using a PZR PORV will result in a loss of RCS inventory. The candidate may conclude that losing RCS inventory is not desirable and incorrectly conclude that the RCS will be depressurized using AUX SPRAY. Part 2 is correct.
✗ C. Incorrect but plausible. Part 1 is correct. For Part 2, the candidate may not understand the expected indications associated with voiding in the upper head region. Consequently, the candidate could incorrectly conclude that there are not indications that voiding is occurring in the upper head region.
Ref: 1-EOP-LOCA-5 (Loss Of Emergency Recirculation) | LO: NOS05LOCA05-04 — Determine the indications that are monitored to ensure proper system/component operation for each step in the EOP for LOSS OF EMERGENCY RECIRCULATION | Source: New | Cognitive: Higher
Connections
- Related systems: Pressurizer & PRT, RCS
- Related EOPs: EOP-LOCA-5 — Loss of Emergency Coolant Recirculation
- Related exam: 2018 NRC Written Exam