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Containment Building + Containment Spray

The containment is the steel-lined concrete structure that contains the RCS, ECCS, RHR, pressurizer relief tank, and other systems processing primary fluid. Its design-basis function is to retain fission-product release inside the building during all design-basis accidents. Containment spray reduces post-LOCA pressure by condensing steam and scrubs iodine from the airborne phase via sodium-hydroxide additive.

Function

Provides the final fission-product barrier per defense-in-depth. Withstands the design-basis containment pressure (~52 psig at Vogtle per UFSAR §3.8.1) without leakage above the licensed value (≤ 0.20% of containment air mass per day). Phase-A isolation closes non-essential penetrations on accident signal; Phase B closes additional penetrations + actuates spray on high-high containment pressure.

Components

flowchart LR
    SHELL["Containment Building<br/>(steel-lined concrete,<br/>~52 psig design)"]
    PEN["Penetrations<br/>(piping, electrical, personnel)"]
    PA["Phase A Isolation<br/>(ventilation, sample lines,<br/>non-essential)"]
    PB["Phase B Isolation «PHASE-B-SIG»<br/>(closes Phase A + adds<br/>component cooling, etc.)"]
    PR["«CTMT-PR»<br/>(containment pressure)"]
    RAD["«CTMT-RAD»<br/>(area radiation)"]
    SUMP["«CTMT-SUMP-LVL»<br/>(recirculation sump)"]
    SPRAY_A(("«CSPRAY-A»"))
    SPRAY_B(("«CSPRAY-B»"))
    HEADER["Spray Header<br/>«SPRAY-FLOW»"]
    NOZZLES["Spray Nozzles<br/>(in upper containment)"]
    NaOH[("Sodium Hydroxide<br/>Tank «NAOH-LVL»<br/>(iodine scrub)")]
    RWST["RWST"]
    SUMP_RECIRC["Sump (recirc mode)"]

    SHELL --> PEN
    PEN --> PA
    PA --> PB
    SHELL -. instruments .-> PR & RAD & SUMP
    RWST --> SPRAY_A & SPRAY_B
    SUMP_RECIRC -. "after ES-1.3" .-> SPRAY_A & SPRAY_B
    NaOH --> SPRAY_A & SPRAY_B
    SPRAY_A & SPRAY_B --> HEADER --> NOZZLES --> SHELL

    classDef boundary stroke:#856404,stroke-width:2px
    classDef isol stroke:#943126,stroke-width:2px
    class SHELL,PEN boundary
    class PA,PB isol
  • Containment vessel — steel-lined reinforced concrete; cylindrical with hemispherical dome; design pressure ~52 psig.
  • Two containment spray pumps — «CSPRAY-A», «CSPRAY-B»; centrifugal; draw from RWST initially, switch to sump per ES-1.3.
  • Spray header + nozzles — array of nozzles in upper containment; spray cone covers most of the free volume.
  • Sodium hydroxide additive tank — «NAOH-LVL»; chemical addition for iodine pH control during spray.
  • Phase A isolation valves — close non-essential penetrations (ventilation, sample lines, instrument air, demin water).
  • Phase B isolation valves — close additional penetrations including some component cooling, with safety functions preserved.
  • Containment penetrations — piping (RHR, SI, charging, containment spray), electrical, instrument lines, personnel/equip hatches.

Instrumentation

  • Containment pressure: «CTMT-PR»
  • Containment temperature: «CTMT-TEMP»
  • Containment area radiation: «CTMT-RAD»
  • Noble-gas activity: «CTMT-NG»
  • Sump level: «CTMT-SUMP-LVL»
  • Spray pump statuses: «CSPRAY-A», «CSPRAY-B»
  • Spray header flow: «SPRAY-FLOW»
  • Spray-additive tank level: «NAOH-LVL»
  • Phase B isolation signal: «PHASE-B-SIG»

Setpoints

Parameter Value Source
Containment design pressure ~52 psig Vogtle UFSAR §3.8.1
Phase B / spray actuation «CTMT-PR» > 17 psig Vogtle Tech Spec 3.3.2
Containment leak-rate LCO (La) 0.20 % / day Vogtle Tech Spec 3.6.1
Spray pump capacity (each) ~3000 gpm Vogtle UFSAR §6.2.2
EAL Site Area Emergency thresholds per NEI 99-01 (containment / radiation) regulatory

Normal alignment

  • Containment closed and pressurized to near atmospheric (slight vacuum or positive depending on ventilation alignment)
  • All isolation valves in normal position; ready to close on accident signal
  • Spray pumps standby, suction aligned to RWST
  • Sodium hydroxide tank at LCO level

Failure modes

  • High containment pressure (RED) — design-basis LOCA inside containment + delayed spray. Response FR-Z.1.
  • Containment flooding (ORANGE) — sump fills past expected level. Response FR-Z.2.
  • High containment radiation (YELLOW) — fuel damage or large primary leak. Response FR-Z.3; EAL classification per NEI 99-01.
  • Sub-atmospheric containment after spray — overcooling by spray exceeds heat source. Lesser hazard; spray modulation addresses.
  • Hydrogen accumulation — post-Fukushima concern; from zirc-water reaction in core damage. Beyond design basis — bridges to SAMG.
  • Isolation valve failure to close on demand — Phase A or Phase B signal received but mechanical/control failure; manual isolation required.

References

  • Vogtle UFSAR §6.2 (Containment systems)
  • Vogtle UFSAR §6.2.2 (Containment heat removal — spray system)
  • Vogtle UFSAR §3.8.1 (Containment structure)
  • Vogtle Tech Spec 3.6 (Containment systems LCOs)
  • NEI 99-01 (EAL methodology)
  • post-Fukushima EA-12-049 (hydrogen control reviewed)