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FR-Z.1 — Response to High Containment Pressure

CSF containment — RED path. Entered when containment pressure
exceeds the containment-spray actuation setpoint (~Phase B containment
isolation signal setpoint, typically 17–28 psig depending on plant; for
Vogtle ~17 psig per Tech Spec 3.3.2) without spray having auto-actuated,
OR when pressure continues rising despite spray operation. Continued
high pressure threatens containment design pressure (~52 psig at Vogtle
per UFSAR §3.8.1) and pushes toward post-Fukushima hydrogen
considerations if hydrogen is being generated by zircaloy oxidation in
the core. Recovery via containment spray + Phase B isolation; if
hydrogen is suspected, the response interfaces with SAMG.

CSF: containment

Step 1 verify-high-pressure

Check: containment pressure «CTMT-PR» above containment-spray actuation setpoint AND rising; Phase B isolation signal «PHASE-B-SIG» status; containment radiation «CTMT-RAD» as a co-indicator
Caution: containment-pressure rise after a LOCA inside containment is expected; FR-Z.1 entry is the rate or magnitude exceeding spray-actuation-setpoint, not normal post-LOCA pressurization
- High pressure confirmed (above spray setpoint, rising or sustained) → #verify-isolation
Because: RED-path response; verify upstream isolation before relying on spray alone
- False alarm, pressure recovered or in normal post-trip band → E-0
Because: return to diagnostic flow

Step 2 verify-isolation

Within: 2 minutes — every minute of unisolated containment with rising pressure adds to release potential
Check: Phase A isolation complete (containment ventilation isolated, sample lines closed, non-essential penetrations closed); Phase B isolation actuated «PHASE-B-SIG»
Action: if Phase A or B not verified complete, manually initiate; verify all containment-isolation-valve indications closed
- Phase A AND Phase B verified or manually initiated → #verify-spray
Because: isolation is prerequisite to effective spray response
- Cannot verify isolation → #verify-spray
Because: parallel-path action — spray initiated alongside continued isolation troubleshooting

Step 3 verify-spray

Within: 5 minutes of high-pressure confirmation
Action: verify containment spray pumps «CSPRAY-A» / «CSPRAY-B» running AND spray flow «SPRAY-FLOW» established
Action: if pumps not auto-running, manually start; verify spray-additive (sodium hydroxide / spray-additive tank «NAOH-LVL») injecting if iodine-removal additive system is in service
Caution: containment spray injects RWST inventory into containment as a fine spray — this is irreversible from containment-cleanup perspective and consumes RWST inventory at ~3000 gpm per train
Caution: spray actuation drives a rapid containment-pressure decrease followed by potential vacuum if heat-removal exceeds source — monitor «CTMT-PR» continuously; sub-atmospheric containment is its own (lesser) hazard
- Spray established AND containment pressure responding → #monitor
Because: spray is performing the containment-pressure-removal function
- Cannot start spray (both pumps unavailable, no flow path) → FR-Z.2
Because: containment-flooding response engages when spray fails — ORANGE-path containment management

Step 4 monitor

Check: containment pressure «CTMT-PR» trend; containment temperature; containment radiation «CTMT-RAD»; spray flow rate sustained
Within: re-evaluate every 5 minutes
- Pressure decreasing toward post-accident no-load (LOCA: ~5-10 psig sustained) → E-0
Because: containment CSF restored to GREEN; return to diagnostic flow
- Pressure continues to rise despite spray → FR-Z.2
Because: spray inadequate; containment-flooding response handles the regime where sump fills before pressure controls

Tags

  • id: CTMT-PR
    description: containment building pressure
    sim-path: containment.pressure
    units: psig
    equipment: containment
    source: Vogtle UFSAR §6.2

  • id: CTMT-RAD
    description: containment area radiation monitor
    sim-path: rad.containment.high_range
    units: rem_per_hr
    equipment: containment
    source: Vogtle UFSAR §6.2

  • id: PHASE-B-SIG
    description: containment Phase B isolation signal (latched)
    sim-path: ess.phase_b.actuation_signal
    units: bool
    equipment: containment
    source: Vogtle UFSAR §6.2

  • id: CSPRAY-A
    description: containment spray pump A status
    sim-path: ess.cspray_pump.a.status
    units: enum[STOPPED,RUNNING,FAULT]
    equipment: containment-spray
    source: Vogtle UFSAR §6.2.2

  • id: CSPRAY-B
    description: containment spray pump B status
    sim-path: ess.cspray_pump.b.status
    units: enum[STOPPED,RUNNING,FAULT]
    equipment: containment-spray
    source: Vogtle UFSAR §6.2.2

  • id: SPRAY-FLOW
    description: containment spray total flow (header)
    sim-path: ess.cspray.header_flow
    units: gpm
    equipment: containment-spray
    source: Vogtle UFSAR §6.2.2

  • id: NAOH-LVL
    description: containment-spray sodium hydroxide additive tank level
    sim-path: ess.cspray.additive_tank.level
    units: percent
    equipment: containment-spray
    source: Vogtle UFSAR §6.2.2