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FR-I.1 — Response to High Pressurizer Level

CSF RCS inventory — ORANGE path. Entered when pressurizer level is
approaching the upper limit (~92% indicated level, where loss of steam
bubble produces "water-solid" pressurizer operation). A solid pressurizer
cannot regulate pressure via the heater-spray-pressure feedback loop —
any further mass addition translates directly to a pressure spike against
the PORVs / safeties. Common drivers: continued SI flow after RCS
inventory is restored, charging-letdown mismatch, surge from cold-leg
injection driving cold water up the surge line.

CSF: rcs-inventory

Step 1 verify-high-level

Check: pressurizer level «PZR-LVL» trending up; charging flow «CHG-FLOW» vs letdown flow «LET-FLOW» imbalance; SI status (any SI flow remaining)
Caution: pressurizer level instrumentation can read high momentarily during a depressurization transient as the steam bubble collapses — verify level trend persists for ≥ 2 min before action
- High level confirmed (level >85% indicated AND rising) → #reduce-makeup
Because: solid pressurizer must be avoided; defensive action while margin remains
- False alarm or transient → E-0
Because: return to diagnostic flow

Step 2 reduce-makeup

Within: 5 minutes — solid pressurizer can occur within minutes if SI is running
Action: throttle charging via «CHG-PUMP-A» / «CHG-PUMP-B» speed control or alignment; place charging on MANUAL low
Action: maximize letdown «LET-FLOW» if VCT is not full and letdown heat-exchanger is available
Action: if SI is still injecting AND RCS conditions justify SI termination per termination criteria (subcooling, heat sink, pressure stable, level recoverable), proceed with SI termination per ES-1.1
Caution: do NOT terminate SI just to reduce pressurizer level — SI termination is governed by the four termination criteria; high pressurizer level alone is not one of them
- Level controlled (stable or decreasing) → #monitor
Because: ORANGE-path action succeeded
- Cannot reduce level despite throttling all makeup → FR-P.1
Because: solid pressurizer + continued mass addition is the PTS precursor when cold-leg injection is the surge source

Step 3 monitor

Check: pressurizer level «PZR-LVL» trend; RCS pressure «PT-455» stability
Within: re-evaluate every 5 min while makeup is throttled
- Pressurizer level stable in normal band (50-70%) → E-0
Because: inventory CSF returned to GREEN
- Solid pressurizer (level pegged high, no steam space) → FR-P.1
Because: PTS-trajectory risk on cold-leg cooldown with high RCS pressure

Tags

  • id: PZR-LVL
    description: pressurizer level
    sim-path: rcs.pressurizer.level
    units: percent
    equipment: pressurizer
    source: Vogtle UFSAR §5.4

  • id: PT-455
    description: pressurizer pressure (wide range)
    sim-path: rcs.pressurizer.pressure_wr
    units: psig
    equipment: pressurizer
    source: Vogtle UFSAR §5.4

  • id: CHG-FLOW
    description: charging flow rate
    sim-path: cvcs.charging.flow
    units: gpm
    equipment: charging-system
    source: Vogtle UFSAR §9.3.4

  • id: LET-FLOW
    description: letdown flow rate
    sim-path: cvcs.letdown.flow
    units: gpm
    equipment: charging-system
    source: Vogtle UFSAR §9.3.4

  • id: CHG-PUMP-A
    description: charging pump A status
    sim-path: cvcs.charging_pump.a.status
    units: enum[STOPPED,RUNNING,FAULT]
    equipment: charging-system
    source: Vogtle UFSAR §9.3.4

  • id: CHG-PUMP-B
    description: charging pump B status
    sim-path: cvcs.charging_pump.b.status
    units: enum[STOPPED,RUNNING,FAULT]
    equipment: charging-system
    source: Vogtle UFSAR §9.3.4