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ES-3.3 — Post-SGTR Cooldown Using Steam Dump

Entered from E-3, ECA-3.3, or ES-3.2 when neither backfill
(ES-3.1) nor controllable blowdown (ES-3.2) is available, and steam
dump — to condenser when available, atmospheric otherwise — is the only
remaining cooldown heat-removal path. Atmospheric dump of ruptured-SG
steam involves continuous radiological release through the ARV; offsite
emergency response must be coordinated.

CSF: heat-sink

CSF: containment

Step 1 align-steam-dump

Decision: select steam-dump pathway based on equipment availability and radiological constraints
1. Condenser steam dump «STEAM-DUMP» available AND condenser-air-ejector activity «AEJ-RAD» within authorized limits — preferred (captures activity in main condenser, secondary release path)
2. Atmospheric relief via ARV «ARV-A» / «ARV-B» / «ARV-C» / «ARV-D» — fallback (direct radiological release, requires SS authorization and emergency-response coordination)
3. Combination — dump intact SGs to condenser while ARVs handle ruptured SG (mitigates total release magnitude)
Caution: do NOT steam-dump from the ruptured SG to the condenser — that contaminates the main condenser and contaminates the secondary side broadly; ruptured-SG release must go via dedicated ARV path
- Condenser available for intact SGs → #cooldown-via-condenser
Because: lowest-release path
- Only atmospheric available → #cooldown-via-atmosphere
Because: ARV is the only option

Step 2 cooldown-via-condenser

Action: cool down intact SGs via condenser steam dump; ruptured SG cooled via slow heat-loss to surroundings (since it cannot dump to condenser)
Caution: ruptured-SG pressure may rise slowly during cooldown (less heat removal than intact SGs); monitor «SG-A-PR» / «SG-B-PR» / «SG-C-PR» / «SG-D-PR» on ruptured SG — if exceeding safety setpoint, ARV release on that SG only
- Condenser cooldown progressing → #monitor
Because: proceed to monitoring
- Condenser lost during cooldown → #cooldown-via-atmosphere
Because: switch to atmospheric path

Step 3 cooldown-via-atmosphere

Within: atmospheric cooldown is throttled — typical rate ≤30 °F/hr below 350 °F to limit radiological release magnitude per unit cooldown
Action: align ARVs «ARV-A» / «ARV-B» / «ARV-C» / «ARV-D» for cooldown; throttle release rate to minimize integrated dose
Caution: atmospheric release of ruptured-SG steam carries radioactive material; coordinate with offsite emergency response; verify EAL classification per NEI 99-01
Caution: ARVs vent at the main-steam-tunnel deflector — release plume direction depends on wind; rad-engineering / ERO must track exposure pathways
- Atmospheric cooldown progressing → #monitor
Because: proceed
- Cannot maintain cooldown → FR-H.1
Because: heat-sink RED-path response

Step 4 monitor

Check: cooldown trajectory; ruptured-SG conditions; total integrated release
Within: re-evaluate every 30 min during continued cooldown
- Cooldown complete to RHR conditions → END
Because: post-SGTR cooldown via steam dump succeeded
- Cooldown stalled → FR-H.1
Because: heat-sink response

Tags

  • id: STEAM-DUMP
    description: condenser steam dump availability (auto-permissive flag)
    sim-path: secondary.steam_dump.available
    units: bool
    equipment: secondary
    source: Vogtle UFSAR §10.4.4

  • id: AEJ-RAD
    description: condenser air-ejector radiation monitor
    sim-path: rad.condenser.air_ejector
    units: cps
    equipment: condenser
    source: Vogtle UFSAR §11.5

  • 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

  • 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