ES-3.2 — Post-SGTR Cooldown Using Blowdown¶
Entered from E-3, ECA-3.2, or ES-3.1 when backfill is
unavailable and the ruptured SG must be blown down to control level
during cooldown. Blowdown to condensate-receiver-tank route is preferred
(captures the activity); atmospheric blowdown is the fallback but
involves direct radiological release through the ruptured SG steam line.
Required Operations approval / EAL coordination before atmospheric
release.
CSF: heat-sink
CSF: containment
Step 1 align-blowdown¶
Check: blowdown path availability — condensate-receiver-tank line «BLOWDOWN-A» path (or B/C/D as identified) AND atmospheric ARV «ARV-A» (or B/C/D) availability; radiation-release projections via plant emergency-dose-projection software
Caution: atmospheric blowdown is a controlled radiological release — must be authorized by SS / Emergency Coordinator before initiation
- Blowdown path available AND radiological release within authorized limits → #initiate-blowdown
Because: ready to blow down
- No safe blowdown path available → ES-3.3
Because: steam-dump alternative procedure
Step 2 initiate-blowdown¶
Within: blowdown is a controlled-rate operation — typical rate determined by ruptured-SG level trend and radiological constraints
Action: open «BLOWDOWN-A» (or B/C/D as identified) to condensate-receiver-tank pathway; verify flow established
Action: monitor radiological release via «MAB-RAD» (main auxiliary building rad) and ARV exhaust monitors if atmospheric path is in use
Action: throttle blowdown to maintain ruptured-SG level in controlled band — too low risks dryout, too high risks overfill
Caution: monitor radiation-release continuously; if release approaches federally-imposed limits, throttle further or stop blowdown and transition to ES-3.3
Note: condensate receiver tank has finite capacity; blowdown must be sequenced with tank-drain operations to keep capacity available
- Blowdown controlled, levels manageable, radiation within limits → #cooldown
Because: blowdown operating; proceed to cooldown loop
- Release approaching limits OR cannot control → FR-Z.3
Because: high-containment-radiation response engages (release path through ruptured SG is functionally equivalent)
Step 3 cooldown¶
Action: cool down using intact SGs at allowable rate (≤50 °F/hr); maintain ruptured-SG blowdown throughout cooldown
Within: cooldown 12-24 hr to RHR cut-in
- Cooldown complete to Mode 4 → END
Because: post-SGTR cooldown via blowdown successful
- Heat sink lost on intact SGs → FR-H.1
Because: heat-sink response
Tags¶
-
id: BLOWDOWN-A
description: SG-A blowdown isolation valve position
sim-path: secondary.blowdown.a.position
units: enum[OPEN,CLOSED]
equipment: sg-a
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: MAB-RAD
description: main auxiliary building area radiation monitor
sim-path: rad.mab.area
units: rem_per_hr
equipment: rad-monitoring
source: Vogtle UFSAR §11.5