Q39 — ESFAS SI Block / Containment High Pressure
013000K4.12 (3.7)
Given:
• Unit 2 is in MODE 3.
• The crew is implementing S2.OP-IO.ZZ-0006, Hot Standby to Cold Shutdown.
• The crew has commenced a cooldown and depressurization to Cold Shutdown to comply with a Technical Specification action requirement.
• RCS Temperature is 535°F
• RCS Pressure is 1890 psig
• All actions for current plant conditions have been completed in accordance with S2.OP-IO.ZZ-0006.
Multiple failures have just occurred resulting in rapid depressurization of ALL Steam Generators (SGs) INSIDE containment causing a Safety Injection actuation.
Which of the following ESFAS initiation signals and logic caused the Safety Injection actuation to occur?
• Unit 2 is in MODE 3.
• The crew is implementing S2.OP-IO.ZZ-0006, Hot Standby to Cold Shutdown.
• The crew has commenced a cooldown and depressurization to Cold Shutdown to comply with a Technical Specification action requirement.
• RCS Temperature is 535°F
• RCS Pressure is 1890 psig
• All actions for current plant conditions have been completed in accordance with S2.OP-IO.ZZ-0006.
Multiple failures have just occurred resulting in rapid depressurization of ALL Steam Generators (SGs) INSIDE containment causing a Safety Injection actuation.
Which of the following ESFAS initiation signals and logic caused the Safety Injection actuation to occur?
A. Containment High Pressure - 2/3 Containment Pressure Channels
B. Pressurizer Pressure Low - 2/3 Pressurizer Pressure Channels
C. Pressurizer Pressure Low – 2/4 Pressurizer Pressure Channels
D. Containment High Pressure – 2/4 Containment Pressure Channels
▶ Show Answer & Explanation
✓ A. Correct. Although the High Steam Flow SI and the Low PZR Pressure SI have been blocked IAW IOP-6, the Containment High Pressure SI at 4 psig is not blocked and an Automatic Safety Injection will occur (4 S/Gs blowing down inside containment).
✗ B. Plausible because the Low Pressurizer Pressure SI signal / logic is 2/3 channels less than 1765 psig and PZR pressure will lower to less than 1765 psig from the SGs blowing down in containment. Incorrect because both the High Steam Flow SI and the Low PZR Pressure SI have been blocked IAW IOP-6. Low Pressurizer PZR Pressure SI is blocked at < 1915 psig (P-11).
✗ C. Plausible because the Low Pressurizer Pressure Reactor Trip is 2/4 channel logic and the candidate may confuse that logic for the SI signal/logic. Incorrect because both the High Steam Flow SI and the Low PZR Pressure SI have been blocked IAW IOP-6. Low Pressurizer PZR Pressure SI is blocked at < 1915 psig (P-11).
✗ D. Plausible because the High-High Containment Pressure (Phase B / Containment Spray) signal logic is 2/4 channels. Incorrect as the Containment High Pressure SI signal /logic is 2/3 channels.
Ref: S2.OP-IO.ZZ-0006, Hot Standby to Cold Shutdown | LO: NOS05ESF000-02, Introduction to Engineering Safety Features and Design Criteria, ELO 21 | Source: New | Cognitive: Comprehension
Connections
- Related systems: RPS/SSPS, Containment
- Related procedures: S2.OP-IO.ZZ-0006 — Hot Standby to Cold Shutdown
- Related exam: 2020 NRC Written Exam