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Exams > 2019 Q50 — PZR Safety Valve Leak and Charging Response

2019 Q50 — PZR Safety Valve Leak and Charging Response

⚠️ DRAFT
Q50 — PZR Safety Valve Leak and Charging Response APE: 008 AK2.03 (2.5)
Given:
• Unit 2 is at 100% Reactor Power
• 23 Charging Pump is in service
• Charging Flow is 88 GPM

At time 11:25:00
• Pressurizer pressure starts to lower due to 2PR3 (PZR SAFETY VLV) seat leakage

At time 11:27:00 (2 Minutes Later)
• Pressurizer pressure is 2100 psig and lowering

At time 11:29:00 (4 Minutes Later)
• Pressurizer pressure is 1910 psig and lowering
• An AUTOMATIC Reactor Trip occurs

Which ONE of the following completes the statement below?

At 11:27, Charging Flow is _(1)_ 88 GPM.
At 11:29, the FIRST-OUT alarm indicates that the Reactor tripped on _(2)_.
A. (1) greater than (2) OTΔT
B. (1) greater than (2) OPΔT
C. (1) less than (2) OTΔT
D. (1) less than (2) OPΔT
▶ Show Answer & Explanation
✓ A. Correct. For Part 1, with seat leakage of the PZR Safety Valve, actual PZR level will lower below program level. Consequently, the master flow controller will automatically raise charging flow in an effort to raise PZR level. Consequently, at 11:27, Charging Flow is greater than 88 GPM (the original charging flow prior to the malfunction). For Part 2, the OTΔT Reactor Trip setpoint is variable and will be automatically lowered as RCS pressure lowers. Consequently, at 11:29, the FIRST-OUT alarm indicates that the Reactor tripped on OTΔT.
✗ B. Part 1 is correct. For Part 2, OPΔT is also a variable Reactor Trip setpoint that changes as AFD changes. Consequently, the candidate could incorrectly conclude that the OPΔT Reactor Trip setpoint changes as RCS pressure changes. This would then cause the candidate to incorrectly conclude that at 11:29, the FIRST-OUT alarm indicates that the Reactor tripped on OPΔT.
✗ C. For Part 1, since the PZR Safety Valves are located on top of the PZR, the candidate could incorrectly conclude that PZR level actually rises due to the PZR Safety Valve seat leakage. When PZR level rises above program level, the master flow controller will actually lower charging flow below 88 GPM (the original charging flow prior to the malfunction). Part 2 is correct.
✗ D. For Part 1, since the PZR Safety Valves are located on top of the PZR, the candidate could incorrectly conclude that PZR level actually rises due to the PZR Safety Valve seat leakage. When PZR level rises above program level, the master flow controller will actually lower charging flow below 88 GPM (the original charging flow prior to the malfunction). For Part 2, OPΔT is also a variable Reactor Trip setpoint that changes as AFD changes. Consequently, the candidate could incorrectly conclude that the OPΔT Reactor Trip setpoint changes as RCS pressure changes. This would then cause the candidate to incorrectly conclude that at 11:29, the FIRST-OUT alarm indicates that the Reactor tripped on OPΔT.
Ref: NOS05FLUNCY-09 (LICENSED OPERATOR FLUENCY LIST), NOS05CVCS00-16 (CHEMICAL AND VOLUME CONTROL SYSTEM) | LO: NOS05CVCS00-16 | Source: New | Cognitive: Higher

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