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Exams > 2018 Q5 — SI Actuation Timing and PZR Heater De-energization

2018 Q5 — SI Actuation Timing and PZR Heater De-energization

⚠️ DRAFT
Q5 — SI Actuation Timing and PZR Heater De-energization 006 ECCS-K6.05 / EA4.09 (4.1)
Given:
• Unit 2 is at 80% Reactor Power and stable
• 21 Charging Pump is in service
• PZR Pressure and Level are lowering
• Containment Pressure is rising

At time 11:00
• PZR Pressure is 1864 psig and lowering
• Containment Pressure is 4.1 psig

At time 11:08
• PZR Pressure is 1764 psig and lowering
• Containment Pressure is 5.2 psig

Which ONE of the following completes the statements below?

_(1)_ is the earliest time that an AUTOMATIC Safety Injection occurred.
The PZR Heaters will de-energize _(2)_.
A. (1) 11:00 — (2) based PZR low level
B. (1) 11:00 — (2) when Safety Injection is actuated
C. (1) 11:08 — (2) based PZR low level
D. (1) 11:08 — (2) when Safety Injection is actuated
▶ Show Answer & Explanation
✓ A. Correct. For Part 1, an automatic Safety Injection occurs when PZR Pressure is < 1765 psig or Containment Pressure is > 4 psig. Consequently, 11:00 is the earliest time that an automatic Safety Injection occurred. For Part 2, the PZR heaters will de-energize based on PZR low level (at 17%).
✗ B. Incorrect but plausible. Part 1 is correct. For Part 2, since the SI signal causes several automatic actions, the candidate could incorrectly conclude that the PZR Heaters de-energize when SI is actuated.
✗ C. Incorrect but plausible. For Part 1, the candidate may recognize that at 11:08, the automatic Safety Injection setpoint for low RCS pressure has been reached and incorrectly determine that 11:08 is the earliest time that an automatic Safety Injection setpoint was reached. Part 2 is correct.
✗ D. Incorrect but plausible. For Part 1, the candidate may recognize that at 11:08, the automatic Safety Injection setpoint for low RCS pressure has been reached and incorrectly determine that 11:08 is the earliest time. For Part 2, since the SI signal causes several automatic actions, the candidate could incorrectly conclude that the PZR Heaters de-energize when SI is actuated.
Ref: NOS05FLUNCY-09 (Licensed Operator Fluency List), NOS05ECCS00-09 (Emergency Core Cooling System), NOS05PZRP&L-10 (Pressurizer Pressure and Level Control) | LO: NOS05PZRP&L-10 — Outline interlocks associated with PZR P&L components | Source: New | Cognitive: Higher

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