SALEM
SALEM STUDY SYSTEM
Systems > Containment

Containment

⚠️ DRAFT

Containment

Function

The containment systems ensure that fission product releases are limited following a LOCA or other design basis accident. The containment structure forms a virtually leak-tight barrier. Heat removal systems (spray and fan coolers) reduce containment pressure and temperature. The containment isolation system provides double barriers on all penetrating lines. (UFSAR 6.1, 6.2)

Containment Structure

ParameterValueSource
TypeSteel-lined reinforced concreteUFSAR 6.2.1.1
Design Pressure47 psigUFSAR 6.2.1.1
Maximum Allowable Leakage Rate0.1% of free volume per day at design pressureUFSAR 6.2.1.1
LinerSteelUFSAR 6.2.1.1
Seismic DesignClass IUFSAR 3.8

Designed to withstand complete blowdown of reactor coolant through any rupture of the RCS up to and including circumferential severance of an RCS pipe. (UFSAR 6.2.1.1)

Containment Spray System

Function

Reduces containment pressure and removes iodine from the containment atmosphere by spraying chemically treated (NaOH) water. (UFSAR 6.2.2.1)

Spray Nozzles

  • Hollow-cone pressure nozzle design, no internal parts subject to clogging
  • 3/8-inch diameter orifice, stainless steel
  • Sauter mean drop size < 1000 microns at design conditions
  • Four 360-degree ring headers at two elevations
  • Screened through 1/12-inch (2.1 mm) holes during recirculation (UFSAR 6.2.2.1)

Operation

Injection Phase:

  • Containment spray pumps take suction from RWST
  • NaOH from spray additive tank mixed with spray flow
  • Spray actuated on High-High containment pressure signal

Recirculation Phase:

  • Spray pumps realigned to containment sump via RHR heat exchangers
  • Cooled recirculated water sprayed into containment (UFSAR 6.2.2.1)

Containment Fan Coil Units (CFCUs)

ParameterValueSource
Number5 per unitUFSAR 6.2.2.2.2
TypeCentrifugal fan with plate fintube cooling coilsUFSAR 6.2.2.2.2
Normal Operation Airflow110000 cfm eachUFSAR 6.2.2.2.2
Accident Operation Airflow40000 cfm eachUFSAR 6.2.2.2.2
Heat Removal (accident, per unit)≥44 x 10⁶ Btu/hr eachUFSAR 6.2.2.2.2
Heat Removal (3 units, cumulative)132 x 10⁶ Btu/hrUFSAR 6.2.2.2.2
Service Water Flow (per unit, accident)Minimum 1300 gpmUFSAR 6.2.2.2.2
LocationOperating floor, between containment wall and polar crane wallUFSAR 6.2.2.2.2
Seismic ClassificationClass IUFSAR 6.2.2.2.2

Each unit includes: motor, fan, motor heat exchanger, cooling coils, roughing filters, dampers, duct distribution system, instrumentation, and controls. Cooled by service water. (UFSAR 6.2.2.2.2)

Containment Internal Pressure Limits

Exam — 2023 Q54
TS 3.6.1.4 requires containment internal pressure between -1.5 and +0.3 psig during Modes 1-4. The upper limit (+0.3 psig) ensures peak pressure does not exceed the 47 psig design pressure during a DBA (LOCA or steam line break). The lower limit (-1.5 psig) ensures the design negative pressure differential of 3.5 psig is not exceeded. If outside limits, must restore within 1 hour.
ParameterValueSource
Upper Pressure Limit+0.3 psigTS 3.6.1.4
Lower Pressure Limit-1.5 psigTS 3.6.1.4
Design Pressure47 psigUFSAR 6.2.1.1
Design Negative Differential3.5 psigTS 3.6.1.4 Bases
Restoration Time1 hourTS 3.6.1.4
Exam — 2018 Q32
LCO 3.6.1.4 (CONTAINMENT INTERNAL PRESSURE) is NOT met when containment pressure exceeds +0.3 psig. Restoration time is 60 minutes (1 hour) or place the Unit in HOT STANDBY within 6 hours. Trap: BEZEL Hi CNTMT Pressure Alarm is 0.2 psid — do not confuse the alarm setpoint (0.2) with the TS limit (+0.3 psig). Other LCOs have 30-minute restoration times (LCOs 3.2.1, 3.2.4, 3.4.10.2, 3.7.2) — do not confuse with the 60-minute LCO 3.6.1.4 time.
Exam — 2020 Q33
PRT rupture disk relief to containment raises containment pressure and temperature. After one hour at 0.1 psig/5 min rise: 0 + 1.2 = 1.2 psig exceeds the +0.3 psig upper limit (LCO 3.6.1.4). At 1 °F/5 min rise: 99 + 12 = 111 °F does NOT exceed the 120 °F limit (LCO 3.6.1.5). Trap: the -1.5 psig is the NEGATIVE pressure limit, not a general magnitude — the positive limit is only 0.3 psig. Also: containment air temperature limit is 120 °F, not 110 °F.
Exam — 2020 Q39
Containment High Pressure SI actuation: 4 psig on 2/3 containment pressure channels. This signal CANNOT be blocked — unlike Low PZR Pressure SI and High Steam Flow SI which can be blocked via P-11 during cooldown per IOP-6. During a Mode 3 cooldown with SI blocks in place, rapid depressurization of all SGs inside containment will raise containment pressure above 4 psig and actuate SI.

Containment Isolation System

Design Basis

Provides double barriers for each line penetrating containment. Automatic isolation on containment isolation signals. (UFSAR 6.2.4)

Isolation Signals

  • Phase A — initiated by SI signal. Closes majority of automatic containment isolation valves.
  • Phase B — initiated by High-High containment pressure (Containment Spray actuation). Closes remaining isolation valves.
  • Containment Ventilation Isolation (CVI) — closes containment purge isolation valves (VC1, VC4) AND pressure/vacuum relief valves (VC5, VC6). (UFSAR 6.3.2, 6.2.4)
Exam — 2020 Q55
Phase A containment isolation valves: CC113 and CC215 (Excess Letdown Component Cooling Valves) receive a Phase A signal to close. Key distinctions:
- CV2 and CV277 (Letdown Isolation Valves) do NOT receive Phase A — they close on low PZR level signal only. They are NOT containment isolation valves. Letdown orifice valves CV3, 4, 5 & 7 ARE Phase A isolation valves.
- CC131 and CC190 (RCP Thermal Barrier) receive a Phase B signal, NOT Phase A.
- BF13s (Feedwater Isolation Valves) receive a Feedwater Isolation Signal, NOT Phase A.
Exam — 2020 Q59
Manually initiating Phase B and Spray Actuation from the Control Room Console also actuates a Containment Ventilation Isolation (CVI) signal. CVI closes ALL purge AND pressure/vacuum relief valves: VC1, VC4, VC5, and VC6. Phase A Isolation does NOT generate a CVI signal. CVI closes all four valves (VC1, 4, 5, 6) — not just the purge isolation valves (VC1, 4).

Containment Air Locks

Exam — 2019 Q28
IAW LCO 3.6.1.3 (Containment Air Locks), the containment airlock interlock mechanisms for BOTH containment airlocks are required to be OPERABLE in MODES 1-4 ONLY. If a containment airlock with ONLY the interlock mechanism inoperable: REQUIRED ACTION B.1 requires verifying an OPERABLE door is closed ONLY (not locked) in the affected air lock within 1 hour. REQUIRED ACTION B.2 then requires locking the OPERABLE door closed within 24 hours. Trap: "closed and locked" is the 24-hour action (B.2), not the 1-hour action (B.1). The immediate 1-hour requirement is closed ONLY.

Containment Atmosphere Iodine Removal

  • Chemically treated spray (NaOH solution) removes elemental iodine vapor by washing action
  • Recirculation through HEPA filter units removes particulates
  • Sump pH maintained 7.0–10.0 to minimize iodine re-evolution and chloride stress corrosion cracking (UFSAR 6.2.3)
Exam — 2019 Q27
CA330 (Control Air Isolation Valve) operability: IAW LCO 3.6.3, CA330s are required to be OPERABLE in MODES 1-4 ONLY. CA330s automatically close on Phase A Containment Isolation at 4 psig. Trap: 15 psig is the Phase B setpoint — not the Phase A setpoint that closes the CA330s.
Exam — 2023 Q52
CA330 Instrument Air Containment Isolation valves close on Phase A signal ONLY — NOT on SI or Phase B. 21 CA330 supplies the 2A control air header; 22 CA330 supplies the 2B control air header. BOTH CA330s must be closed to fully isolate instrument air to containment (each is in a separate air supply line with its own check valve). Backup air receivers inside containment provide PORV air supply during EOP actions.
Exam — 2022 Q59
Containment Iodine Removal Units (IRUs): should only be placed in service when directed by Radiation Protection (or at the discretion of SM/CRS for testing). IRUs can ONLY be operated from the main control room — NOT from the Hot Shutdown Panel. IRUs are NOT directed by EOPs — they are placed in service at Radiation Protection's request when iodine is present in containment.

Combustible Gas Control

  • Hydrogen generated post-LOCA from: zirconium-water reaction, corrosion of aluminum/zinc, radiolysis
  • Hydrogen monitoring provided in containment
  • Hydrogen purge capability (UFSAR 6.2.5)

Engineered Safety Features Summary

ESF SystemFunctionSource
Containment StructureLeak-tight barrier for fission productsUFSAR 6.1
ECCSBorated water injection for core coolingUFSAR 6.3
Containment SprayPressure reduction + iodine removalUFSAR 6.2.2.1
CFCUsAtmosphere recirculation and coolingUFSAR 6.2.2.2
Containment IsolationDouble barriers on penetrationsUFSAR 6.2.4

Tech Spec LCOs

  • TS 3/4.6 — Containment — Containment integrity, leakage
  • TS 3/4.6 — Containment|TS 3/4.6.1 — Containment Integrity
  • TS 3/4.6 — Containment|TS 3/4.6.2 — Depressurization and Cooling Systems (spray, fan coolers)
  • TS 3/4.6 — Containment|TS 3/4.6.3 — Containment Isolation Valves
  • TS 3/4.6 — Containment|TS 3/4.6.4 — Combustible Gas Control
  • TS 3/4.6 — Containment|TS 3/4.6.5 — Containment Structural Integrity
Exam — 2023 Q58
Hydrogen Recombiner System: per EOP-LOCA-1 step 17, only one hydrogen recombiner is allowed in service when containment hydrogen concentration is between >0.5% and <4%. Operation of both hydrogen recombiners is not permitted. The purpose is to reduce hydrogen concentration to prevent formation of a flammable mixture that could ignite and cause a pressure excursion challenging containment integrity.
Exam — 2020 Q92
Per EOP-LOCA-1 Step 24, hydrogen concentration decision points: 0.5% to 4.0% → start only ONE recombiner. ≥ 4.0% → consult TSC. S2.OP-SO.CAN-0001 (normal operating procedure) starts two recombiners if H2 is 2.0% and rising. The EOP limits to one recombiner — do not confuse the two procedures.
Exam — 2019 Q32
Hydrogen recombiner reference powers: 21 Recombiner = 43.68 KW, 22 Recombiner = 42.63 KW. With CURRENT pressure 4.0 psig and PRIOR-to-LOCA temperature 90°F → Cp = 1.21 → 21 Recombiner power setting = 43.68 x 1.21 = 52.85 → rounded to 54 KW.
Exam — 2022 Q60
Hydrogen recombiner power setting calculation (per S2.OP-SO.CAN-0001): Power Setting = Cp (pressure correction factor) x Reference Power. Use the CURRENT containment pressure and the PRIOR-to-LOCA containment temperature to select Cp from Attachment 2. Round up to the next higher setting readable on the meter. Example: 22 Hydrogen Recombiner at 5 psig and 90F pre-LOCA: Cp=1.24, Ref Power=42.63 KW → 52.86 KW → rounded to 54 KW. Use pre-LOCA temperature (not current), and current pressure (not peak) for Cp selection.
Exam — 2023 Q63
Fire Protection Containment Isolation (2FP147): on a valid fire detected inside containment (Zones 59 and 74 on 2RP5), 2FP147 must be manually opened from the 2RP5 panel — it does NOT automatically open. However, 2FP147 WILL automatically close on a Phase A containment isolation signal.
Exam — 2020 Q75
Confirms 2FP147 containment fire response sequence: after OHA A-7 and 2RP5 indicate fire in containment (Zone 59 and Zone 74 lit), crew trips Reactor, Turbine, and all RCPs, enters EOP-TRIP-1. NEXT action per AB.FIRE-0001 is to OPEN 2FP147 from the control room. Fire pumps start only after 2FP147 is opened. Containment deluge valves are automatic. PORV BLOCK valve EMER CLOSE is the relay room fire response, not containment fire.
Exam -- 2023 Q95
FHB BLDG AIR D/P LO alarm during fuel moves: per S2.OP-AR.ZZ-0011, the FIRST action is to suspend movement of irradiated fuel assemblies, THEN validate the alarm using the local indicator. If the alarm is invalid and will not clear, per S2.OP-IO.ZZ-0010, the local indicator MAY be used to continuously monitor FHB D/P as a compensatory measure -- fuel moves may resume with continuous local monitoring. Trap: validating the alarm is performed AFTER suspending fuel moves, not before.
Exam -- 2023 Q100
Fire protection: with both Salem fire pumps inoperable, per AB.FP-0001: open backup fire suppression water supply cross-tie valves from Hope Creek. If cross-tie cannot be established within 24 hours, unit must be in Hot Standby within 6 hours, then Hot Shutdown within the following 6 hours, then Cold Shutdown within the subsequent 24 hours.
JPM — 2023 SRO-A2
IST containment ventilation valve surveillance review: 2VC13 in REQUIRED ACTION RANGE — declare inoperable, enter TS LCO 3.6.3 (4 hours to restore/isolate or begin shutdown). 2VC12 in REQUIRED EVALUATION RANGE — immediately retest or declare inoperable.
JPM — 2023 Sim-h
Containment pressure relief: upon OHA A-6 (RMS HI RAD OR TRBL) alarm on 2R41D with automatic isolation defeated, must manually close PRESSURE RELIEF DAMPER, 2VC6, and 2VC5 to isolate the radiological release.

Fire Protection

  • Fire detection and alarm system throughout the plant
  • Water supply (fire water pumps, sprinklers, standpipes)
  • CO₂, Halon, and dry chemical suppression in specific areas
  • Safe shutdown capability analysis per 10CFR50 Appendix R
  • RCP oil collection system prevents fire spread from oil leaks (UFSAR 9.5.1)

Adverse Containment Conditions

Definition

Adverse containment conditions exist when containment pressure is elevated above normal, typically >= 4 psig. This affects multiple EOP setpoints and action criteria because elevated containment pressure degrades instrument accuracy and changes thermal-hydraulic behavior.

Adverse Containment Triggers for SMM

Exam — 2020 Q26
Adverse containment conditions for the Subcooling Margin Monitor (SMM) are triggered by EITHER containment pressure > 4 psig OR containment radiation (R44A/B) > 1E05 R/HR — only one condition is required. Pressure-driven adverse signal auto-resets when pressure drops below 3 psig. Radiation-driven adverse signal does NOT auto-reset — requires manual action even after radiation levels drop below the adverse threshold.

Impact on EOP Parameters

When adverse containment conditions exist, EOP setpoints for level instruments are adjusted upward to account for the effect of containment pressure on instrument readings:

ParameterNormal ContainmentAdverse Containment
SG NR level for RCP start (EOP-FRCC-1)>= 9%>= 15%

Why It Matters

  • SG narrow range level transmitters are affected by containment pressure because the reference leg is inside containment
  • Higher containment pressure depresses the indicated level reading
  • EOPs use higher setpoint values under adverse containment to ensure actual conditions support the intended action
Exam — 2023 Q84
With containment pressure at 5 psig (adverse conditions), the required SG NR level for RCP start in EOP-FRCC-1 is >= 15% instead of the normal 9%. Trap: using normal containment criteria when adverse conditions exist will overestimate the number of available RCPs.
JPM — 2022 RO-A1
EOP-FRCI-3 Attachment 1 hydrogen vent time calculation uses containment free volume at STP: V = 2.62E06 x Tfact where Tfact = 492/Tabs. At 140F containment temp: Tabs = 600R, Tfact = 0.82, V = 2148400 ft3. Maximum allowable hydrogen concentration is 3.0% — vent volume limited to (3.0% - current H2%) x V / 100%.

Connections