SALEM
SALEM STUDY SYSTEM
EOPs > EOP-CFST-1 — Critical Safety Function Status Trees

EOP-CFST-1 — Critical Safety Function Status Trees

⚠️ DRAFT

EOP-CFST-1 — Critical Safety Function Status Trees

Purpose

Provides the decision logic for monitoring Critical Safety Functions (CSFs) during emergency operations. Continuously evaluated after a reactor trip to detect degraded or lost safety functions, with color-coded paths (Red, Purple, Yellow) directing entry into the appropriate Functional Restoration Procedure (FRP).

Key Actions / Information

Exam — 2020 Q24
Core Cooling Red Path validation criteria (with no RCPs running): five (5) hottest CETs > 700°F AND RVLIS Full Range ≤ 39%. RVLIS Upper Range is NOT applicable for core cooling status — it only provides indication from the hot leg piping connection to the top of the reactor vessel. Purple Path (degraded core cooling) uses RVLIS Dynamic Range ≤ 44%. For CET-based Red Path (inadequate core cooling), five (5) CETs must be > 1200°F (not three).
Exam — 2020 Q26
Subcooling Margin Monitor (SMM) adverse containment inputs: containment pressure > 4 psig OR containment radiation (R44A/B) > 1E05 R/HR — either condition alone triggers ADVERSE mode. When containment pressure lowers to < 3 psig, the SMM automatically resets from a pressure-driven adverse condition. The SMM does NOT automatically reset when radiation levels lower below the adverse threshold — manual action is required to reset from a radiation-driven adverse condition.
Exam — 2018 Q47
Confirms CSF/color hierarchy priority: with Heat Sink Red and Core Cooling Purple, address Heat Sink first because color (Red > Purple) takes precedence over CSF hierarchy position (Core Cooling > Heat Sink). Also confirms: with Red and Purple CFSTs, monitoring frequency is continuous (not every 10-20 minutes, which is for no condition more serious than Yellow).
Exam — 2019 Q46
CSF Hierarchy (high to low): SHUTDOWN MARGIN, CORE COOLING, HEAT SINK, THERMAL SHOCK, CONTAINMENT ENVIRONMENT, COOLANT INVENTORY. CFST Color Hierarchy (high to low): Red, Purple, Yellow, Green. Color takes precedence over CSF position — a Red path for Heat Sink takes priority over Purple path for Shutdown Margin or Core Cooling. Example: with Core Cooling Purple and Heat Sink Red → address Heat Sink FIRST. Trap: candidates may default to the CSF hierarchy (Shutdown Margin > Core Cooling > Heat Sink) and address Core Cooling first, but the color hierarchy overrides — Red always beats Purple regardless of CSF position.
Exam — 2019 Q75
Containment Environment CFST FRCE-2 (Yellow — Containment Flooding) entry: Containment Sump level ~78% (75% ADVERSE). Other containment environment CFSTs: FRCE-1 Red (containment pressure ~47 psig), FRCE-1 Purple (containment pressure ~15 psig with CS pump running), FRCE-3 Yellow (containment radiation ~2 R/HR). FRCE-2 is triggered by sump level, not pressure or radiation. Know which parameter drives each color path.
Exam — 2018 Q85
Containment environment CFST: FRCE-3 entry at R44A/B ≥ 2 R/HR. At 14:00, R44A/B = 2 R/HR → entry conditions met. At 15:00, R44A/B = 100 R/HR → warning setpoint (not the entry condition). 2 R/HR is the CFST threshold, NOT 100 R/HR. The 100 R/HR is the R44A/B WARNING setpoint which is unrelated to the CFST entry condition.
Exam — 2018 Q74
Containment Environment CFST — containment flooding (FRCE-2) entry thresholds: Normal containment: 78% sump level; Adverse containment: 75% sump level. With normal containment conditions, the crew enters EOP-FRCE-2 when sump level reaches 78%, not 75%.
Exam — 2018 Q75
Adverse containment radiation threshold: R44A/B > 1E05 R/HR. At 7E2 R/HR (700 R/HR), containment is NORMAL. R44A/B alarm actuation does NOT mean adverse containment. The alarm threshold is much lower than the 1E05 R/HR adverse threshold.
Exam — 2018 Q80
Heat Sink CFST entry criteria for FRHS-1 (Red path): ALL SG NR Levels < 15% AND Total Feedwater Flow < 22E04 LB/HR. Both conditions must be met — low NR levels alone is not sufficient.

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