FR-P.2 — Response to Anticipated Pressurized Thermal Shock Condition¶
CSF RCS integrity — ORANGE path. Entered when RCS pressure-
temperature trajectory is heading toward the PTS limit curve but is not
yet imminently crossing. Slower-rate cooldown with continued SI;
operator action limits cooldown rate to keep trajectory inside the
Tech-Spec curve. Distinct from FR-P.1 (RED): here there is time to
adjust rate rather than emergency-stop SI; the curve is being
approached, not crossed.
CSF: rcs-integrity
Step 1 verify-trend¶
Check: (T_cold from lowest of «TE-411-COLD» / «TE-421-COLD» / «TE-431-COLD» / «TE-441-COLD», P_RCS «PT-455») trajectory inside PTS curve with negative margin trending toward zero; cooldown rate exceeding Tech Spec curve guidance (typically ≤100 °F/hr below 350 °F)
- Trajectory trending toward limit (margin shrinking, cooldown rate elevated) → #limit-rate
Because: ORANGE-path action limits rate before trajectory becomes imminent
- Trajectory stable, margin positive and not shrinking → E-0
Because: false alarm or stable; return to diagnostic flow
Step 2 limit-rate¶
Within: 10 minutes — PTS-rate margin recovery has slower time constants than RED-path response
Action: throttle SI flow «SI-PUMP-A» / «SI-PUMP-B» to the minimum subcooling demand
Action: throttle steam-dump or atmospheric-relief flow to reduce primary-cooldown rate; aim for ≤50 °F/hr below 350 °F (conservative ramp)
Action: energize pressurizer heaters «PZR-HTR» to maintain pressurizer level and offer additional heat input
Caution: ORANGE-to-RED transition can occur if SG depressurization or LOCA mass loss accelerates cooldown; if cold-leg temperature drops faster than 100 °F/hr immediately escalate to FR-P.1
- Cooldown rate within Tech Spec AND trajectory off PTS approach → #monitor
Because: ORANGE-path response succeeded; transition to monitoring
- Trajectory worsening despite rate-limit actions → FR-P.1
Because: RED-path PTS response is required
Step 3 monitor¶
Check: (T_cold, P_RCS) trajectory vs PTS curve; cooldown rate trend
Within: re-evaluate every 10 minutes; PTS criteria are evaluated continuously throughout cooldown
- Trajectory clear of PTS curve with positive margin AND rate within Tech Spec → E-0
Because: RCS integrity CSF returned to GREEN; return to diagnostic flow
- Trajectory becoming imminent (rate accelerating or curve being approached fast) → FR-P.1
Because: RED-path response engages
Tags¶
-
id: PT-455
description: pressurizer pressure (wide range)
sim-path: rcs.pressurizer.pressure_wr
units: psig
equipment: pressurizer
source: Vogtle UFSAR §5.4 -
id: TE-411-COLD
description: RCS loop 1 cold-leg temperature
sim-path: rcs.loop1.t_cold
units: degF
equipment: rcs-loop-1
source: Vogtle UFSAR §5.1.1 -
id: TE-421-COLD
description: RCS loop 2 cold-leg temperature
sim-path: rcs.loop2.t_cold
units: degF
equipment: rcs-loop-2
source: Vogtle UFSAR §5.1.1 -
id: TE-431-COLD
description: RCS loop 3 cold-leg temperature
sim-path: rcs.loop3.t_cold
units: degF
equipment: rcs-loop-3
source: Vogtle UFSAR §5.1.1 -
id: TE-441-COLD
description: RCS loop 4 cold-leg temperature
sim-path: rcs.loop4.t_cold
units: degF
equipment: rcs-loop-4
source: Vogtle UFSAR §5.1.1 -
id: SI-PUMP-A
description: high-head SI pump A status
sim-path: ess.si_pump.a.status
units: enum[STOPPED,RUNNING,FAULT]
equipment: si-system
source: Vogtle UFSAR §6.3 -
id: SI-PUMP-B
description: high-head SI pump B status
sim-path: ess.si_pump.b.status
units: enum[STOPPED,RUNNING,FAULT]
equipment: si-system
source: Vogtle UFSAR §6.3 -
id: PZR-HTR
description: pressurizer heater bank energization status
sim-path: rcs.pressurizer.heaters.status
units: enum[OFF,ON,FAULT]
equipment: pressurizer
source: Vogtle UFSAR §5.4