Skip to content

ECA-3.2 — SGTR with Loss of Reactor Coolant — Saturated Recovery

Entered from E-3 or ECA-3.1 when SGTR with inventory loss has
progressed to saturated RCS — subcooling lost, pressurizer level low or
empty. Cooldown trajectory is constrained by saturation; pressurizer
recovery is not viable until cooldown allows RCS pressure to drop.
RCS pressure tracks ruptured-SG pressure during saturated cooldown
(thermodynamic equilibrium).

CSF: core-cooling

CSF: rcs-inventory

CSF: containment

Step 1 confirm-saturated

Check: subcooling margin «SUB-MARGIN» at or near zero; pressurizer level «PZR-LVL» off-scale low or empty; core-exit thermocouples «CET-AVG» at T_sat; RVLS «RVLS-DYN» showing voiding above core
Caution: saturated SGTR is the FR-C.1 precursor — if vessel level drops or CETs go superheated, escalate immediately
- Saturated confirmed → #stabilize-inventory
Because: saturated-recovery procedure engages
- Subcooling restored (transient saturation only) → ECA-3.1
Because: subcooled-recovery resumes

Step 2 stabilize-inventory

Action: maintain SI «SI-PUMP-A» / «SI-PUMP-B» flow at maximum available; allow RCS pressure «PT-455» to track ruptured-SG pressure «SG-A-PR» / «SG-B-PR» / «SG-C-PR» / «SG-D-PR» (the equilibrium condition under saturated SGTR)
Action: verify core cooling adequate via CET «CET-AVG» and RVLS «RVLS-DYN» — must remain at T_sat with core covered, NOT superheating
Caution: monitor for inadequate core cooling continuously; any CET superheating or RVLS dropping toward core elevation escalates to FR-C.1
- Inventory stable (CETs at T_sat, RVLS stable above core) → #cooldown-saturated
Because: ready to cool down via intact-SG path
- Inventory loss continuing → FR-C.1
Because: inadequate-core-cooling response

Step 3 cooldown-saturated

Action: cool down using intact SGs at maximum Tech Spec allowable rate (100 °F/hr) via condenser dump or ARVs «ARV-A» / «ARV-B» / «ARV-C» / «ARV-D» on intact SGs
Within: speed matters — every minute of saturated SGTR drives continuing radiological release through the ruptured SG
Note: as cooldown progresses, ruptured-SG pressure drops in parallel with RCS pressure; subcooling will return as cooldown succeeds, allowing transition back to ECA-3.1 trajectory
- Cooldown achieved AND subcooling restored → ES-3.2
Because: post-SGTR blowdown cooldown procedure
- Cooldown not progressing → ECA-3.3
Because: alternative pressure-control procedure when steam-dump path is impaired

Tags

  • id: SUB-MARGIN
    description: RCS subcooling margin (T_sat at PT-455 minus hot-leg temperature)
    sim-path: rcs.subcooling_margin
    units: degF
    equipment: rcs
    source: Vogtle UFSAR §15.6

  • id: PT-455
    description: pressurizer pressure (wide range)
    sim-path: rcs.pressurizer.pressure_wr
    units: psig
    equipment: pressurizer
    source: Vogtle UFSAR §5.4

  • id: PZR-LVL
    description: pressurizer level
    sim-path: rcs.pressurizer.level
    units: percent
    equipment: pressurizer
    source: Vogtle UFSAR §5.4

  • id: CET-AVG
    description: core-exit thermocouple average (5+ representative locations across the core)
    sim-path: rcs.core_exit.thermocouple.avg
    units: degF
    equipment: rcs
    source: Vogtle UFSAR §7.5

  • id: RVLS-DYN
    description: reactor vessel level indication system, dynamic-pressure-compensated channel
    sim-path: rcs.rvls.dynamic.level
    units: percent_collapsed_liquid
    equipment: rcs
    source: Vogtle UFSAR §7.5

  • 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: SG-A-PR
    description: SG-A steam pressure
    sim-path: secondary.sg.a.steam_pressure
    units: psig
    equipment: sg-a
    source: Vogtle UFSAR §10.3

  • id: SG-B-PR
    description: SG-B steam pressure
    sim-path: secondary.sg.b.steam_pressure
    units: psig
    equipment: sg-b
    source: Vogtle UFSAR §10.3

  • id: SG-C-PR
    description: SG-C steam pressure
    sim-path: secondary.sg.c.steam_pressure
    units: psig
    equipment: sg-c
    source: Vogtle UFSAR §10.3

  • id: SG-D-PR
    description: SG-D steam pressure
    sim-path: secondary.sg.d.steam_pressure
    units: psig
    equipment: sg-d
    source: Vogtle UFSAR §10.3

  • id: ARV-A
    description: SG-A atmospheric relief valve position
    sim-path: secondary.arv.a.position
    units: enum[OPEN,CLOSED,INTERMEDIATE]
    equipment: sg-a-msl
    source: Vogtle UFSAR §10.3.2

  • id: ARV-B
    description: SG-B atmospheric relief valve position
    sim-path: secondary.arv.b.position
    units: enum[OPEN,CLOSED,INTERMEDIATE]
    equipment: sg-b-msl
    source: Vogtle UFSAR §10.3.2

  • id: ARV-C
    description: SG-C atmospheric relief valve position
    sim-path: secondary.arv.c.position
    units: enum[OPEN,CLOSED,INTERMEDIATE]
    equipment: sg-c-msl
    source: Vogtle UFSAR §10.3.2

  • id: ARV-D
    description: SG-D atmospheric relief valve position
    sim-path: secondary.arv.d.position
    units: enum[OPEN,CLOSED,INTERMEDIATE]
    equipment: sg-d-msl
    source: Vogtle UFSAR §10.3.2