ECA-3.3 — SGTR Without Pressurizer Pressure Control¶
Entered from E-3, ECA-3.1, or ECA-3.2 when pressurizer
pressure control is lost — failed PORV (stuck or unresponsive), lost
pressurizer heaters, lost normal/auxiliary spray. Without pressurizer
control, RCS pressure is determined by the balance of SI inflow, SGTR
outflow, and SG-pressure equalization. SG steam dump becomes the
primary pressure-control mechanism. Final SGTR-recovery procedure;
last cooldown path before SAMG.
CSF: core-cooling
CSF: rcs-inventory
CSF: containment
Step 1 verify-pressure-control-loss¶
Check: pressurizer PORVs «PORV-456A» / «PORV-456B» status (stuck or unresponsive); pressurizer heaters «PZR-HTR» (failed or de-energized); normal/auxiliary spray valves (failed); RCS pressure «PT-455» drifting uncontrollably (rising despite no SI, OR dropping despite normal makeup)
Caution: differentiate pressure-control loss from inadequate-control — losing a single PORV is recoverable via block valves; ECA-3.3 entry is multi-channel pressure-control failure
- Pressure control loss confirmed → #use-steam-dump
Because: extreme-conditions response engages
- Pressure control restored (single PORV recoverable, spray restorable) → E-3
Because: standard SGTR procedure can continue
Step 2 use-steam-dump¶
Within: 5 minutes — uncontrolled RCS pressure with SGTR drives continuing release; corrective action immediate
Action: control RCS pressure indirectly via SG steam dump — opening intact-SG ARVs «ARV-A» / «ARV-B» / «ARV-C» / «ARV-D» reduces secondary pressure, which by primary-secondary thermodynamic coupling lowers RCS pressure
Action: modulate SI «SI-PUMP-A» / «SI-PUMP-B» flow to balance mass addition against leak rate; lower SI rate reduces RCS-pressurization driver but threatens core cooling
Caution: balance leak termination against RCS overcooling — aggressive cooldown drives PTS-trajectory; if «TE-411-COLD» rate of fall exceeds 100 °F/hr, branch to FR-P.1
- Pressure controllable via steam-dump path → #cooldown-via-steam-dump
Because: pressure-control alternative established; proceed to cooldown
- Cannot control pressure even with steam dump → FR-P.1
Because: PTS-trajectory response is the consequence of uncontrolled cooldown
Step 3 cooldown-via-steam-dump¶
Action: cool down using intact-SG steam dump while managing ruptured-SG inventory (let it bleed down as RCS pressure decreases)
Within: cooldown to RHR conditions typically takes 12-24 hr
Note: under this regime the ruptured SG will partially or fully drain as cooldown proceeds; that's an acceptable outcome since the leak is terminating by pressure equalization
- Recovery progressing → ES-3.3
Because: post-SGTR steam-dump cooldown procedure handles ongoing recovery
- Conditions degrading toward inadequate core cooling → FR-C.1
Because: RED-path response
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: PORV-456A
description: pressurizer PORV 456A position
sim-path: rcs.pressurizer.porv.456a.position
units: enum[OPEN,CLOSED,INTERMEDIATE]
equipment: pressurizer
source: Vogtle UFSAR §5.4 -
id: PORV-456B
description: pressurizer PORV 456B position
sim-path: rcs.pressurizer.porv.456b.position
units: enum[OPEN,CLOSED,INTERMEDIATE]
equipment: pressurizer
source: Vogtle UFSAR §5.4 -
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 -
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: 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: 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