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SALEM STUDY SYSTEM
Systems > Steam Generator & Blowdown

Steam Generator & Blowdown

⚠️ DRAFT

Steam Generator & Blowdown

Function

The steam generators transfer heat from the reactor coolant (primary side) to the feedwater (secondary side) to produce steam for the turbine-generator. They are vertical shell and U-tube evaporators with integral moisture separating equipment. (UFSAR 5.1, 5.5.2)

Key Design Parameters — Unit 1 (Model F)

ParameterValueSource
Number4UFSAR T5.2-5A
ModelWestinghouse Model F (replacement)UFSAR T5.2-5A
Design Pressure (primary/secondary)2485 / 1185 psigUFSAR T5.2-5A
Primary Hydrostatic Test Pressure (cold)3107 psigUFSAR T5.2-5A
Design Temperature (primary/secondary)650 / 600°FUFSAR T5.2-5A
Heat Transfer Surface Area55050 ft²UFSAR T5.2-5A
Heat Transferred2961 x 10⁶ Btu/hrUFSAR T5.2-5A
Number of U-tubes5626UFSAR T5.2-5A
U-tube OD0.688 inUFSAR T5.2-5A
Tube Wall Thickness (min)0.041 inUFSAR T5.2-5A
Tube MaterialInconelUFSAR 5.1
Overall Height67 ft 8 inUFSAR T5.2-5A
Shell OD (upper/lower)176.25 / 135.42 inUFSAR T5.2-5A
RC Volume (rated load)966.1 ft³UFSAR T5.2-5A
Steam Pressure at Full Load (High Tavg)869 psiaUFSAR T5.2-5A
Steam Pressure at Full Load (Low Tavg)778 psiaUFSAR T5.2-5A
Steam Flow at Full Load3.76–3.78 x 10⁶ lb/hrUFSAR T5.2-5A
Maximum Moisture Carryover0.25 wt%UFSAR T5.2-5A
Feedwater Temperature432.8°FUFSAR T5.2-5A

Key Design Parameters — Unit 2 (AREVA NP Model 61/19T)

ParameterValueSource
Number4UFSAR T5.2-5
ModelAREVA NP Model 61/19T (replacement)UFSAR T5.2-5
Design Pressure (primary/secondary)2485 / 1185 psigUFSAR T5.2-5
Primary Hydrostatic Test Pressure (cold)3107 psigUFSAR T5.2-5
Design Temperature (primary/secondary)650 / 600°FUFSAR T5.2-5
Heat Transfer Surface Area66236 ft²UFSAR T5.2-5
Heat Transferred2961 x 10⁶ Btu/hrUFSAR T5.2-5
Number of U-tubes5048UFSAR T5.2-5
U-tube OD0.750 inUFSAR T5.2-5
Tube Wall Thickness (min)0.043 inUFSAR T5.2-5
Tube MaterialInconel 690 thermally treatedUFSAR 5.1
Shell OD (upper/lower max)175.75 / 135.0 inUFSAR T5.2-5
RC Volume (rated load)1201 ft³UFSAR T5.2-5
Steam Pressure at Full Load (High Tavg)900 psiaUFSAR T5.2-5
Steam Pressure at Full Load (Low Tavg)805 psiaUFSAR T5.2-5
Steam Flow at Full Load3.76–3.77 x 10⁶ lb/hrUFSAR T5.2-5
Maximum Moisture Carryover< 0.1 wt%UFSAR T5.2-5
Feedwater Temperature432.8°FUFSAR T5.2-5

Unit Differences

FeatureUnit 1 (Model F)Unit 2 (Model 61/19T)
Number of U-tubes56265048
Tube OD0.688 in0.750 in
Tube MaterialInconelInconel 690 TT
Heat Transfer Area55050 ft²66236 ft²
Steam Pressure (High Tavg)869 psia900 psia
Primary claddingAustenitic SS (channel heads), Inconel (tubesheet)Austenitic SS (Type 308L/309L) or Inconel 600
Max Moisture Carryover0.25 wt%< 0.1 wt%

SG Blowdown Radiation Monitoring

Exam — 2020 Q51
R19 SGBD radiation monitor WARNING setpoint — unit difference: Unit 1 WARNING causes NO automatic actuations. Unit 2 WARNING automatically closes ALL GB10s, GB185s, and 2GB50. At the ALARM setpoint: Unit 1 closes ALL GB4s, GB8s, GB10s, GB185s, and 1GB50; Unit 2 isolates blowdown from the affected SGs by closing the associated GB4. Do not confuse WARNING actions (unit-specific, limited) with ALARM actions (more extensive isolation on both units).

Construction

  • Reactor coolant flows through inverted U-tubes, entering and leaving through nozzles in the hemispherical bottom head
  • Bottom head divided into inlet and outlet chambers by vertical partition plate
  • Manways provided for access to both sides of divided head
  • Steam generated on shell side flows upward through moisture separators to outlet nozzle at top
  • Units are primarily carbon steel
  • (UFSAR 5.1)
Exam — 2023 Q2
Natural circulation verification: RCS subcooling >0°F (T-sat at RCS pressure minus highest CET), SG pressures stable or lowering, T-hots stable or dropping, CETs lowering, T-colds at saturation temperature for SG pressure. RCS T-cold matching SG saturation temp confirms heat transfer from primary to secondary through SG tubes is established.
Exam — 2023 Q42
SG high level trip (P-14): 2/3 NR levels ≥67% on any SG → main turbine trip → reactor trip. FW Isolation closes BF13, BF19, BF40 and trips SGFPs. If BF19 fails open, SG level continues to rise until trip on high level.
Exam — 2022 Q11
Natural circulation monitoring (EOP-SGTR-1 step 38.1): RCS T-Cold in unaffected loops should be approximately 548°F (saturation at MS10 setpoint 1015 psig / 1030 psia). Affected SG MS10 set to 1045 psig (1060 psia) → Tsat ~552°F. With LOOP, steam dumps unavailable — use atmospheric relief valves (MS10s) on intact SGs.

Tech Spec LCOs

  • TS 3/4.4 — Reactor Coolant System|TS 3/4.4.5 — Steam Generators (tube integrity, inspection requirements)
Exam — 2023 Q81
SG tube leak action levels per AB.SG-0001 Attachment 1: with leak rate >= 75 gpd AND rate of change >= 30 gpd/hr, Action Level 3 requires reduce power to <= 50% in 1 hour and MODE 3 in the following 2 hours. Trap: a 125 gpd leak rate trending at 30 gpd/hr meets the rate-of-change criterion for Action Level 3, not the 150 gpd absolute threshold (which requires MODE 3 in 6 hours).
Exam — 2023 Q85
Security-redacted question testing SRO knowledge of EOP-FRHS-2, Response to Steam Generator Overpressure, in conjunction with security event procedures (K/A W/E13 G2.4.28). Reference: 2-EOP-FRHS-2 (R41).
JPM — 2023 SRO-A4
ICMF peer check during SGTR: a release IS in progress because the TD AFW pump takes steam from 21 and 23 SGs — with 23 SG ruptured and 23MS45 not closed, primary-to-secondary leakage exits through the TD AFW pump steam supply. No radiation monitor monitors this release path = unmonitored release in progress.
Exam — 2022 Q81
EOP-FRHS-1 heat sink established criteria (Step 6): heat sink is established when NR level in at least one SG is >9% (15% adverse) OR feed flow is verified to at least one SG by CETs lowering or WR level rising. If WR level is rising in one SG (even with all NR levels offscale low), heat sink IS established and transition back to the procedure in effect (e.g. EOP-TRIP-2) IS allowed. NR level does not need to reach 9% before returning — WR level rising is sufficient to confirm feed flow and allow exit from FRHS-1.
Scenario — 2022 #4
23 SG tube leak (25-30 gpm) progressing to design basis 650 gpm tube rupture. Diagnostic indications: RMS alarms 2R15, 2R19C (23 SG B/D), 2R53C (MS Line), PZR level lowering. Transfer to centrifugal charging pump stabilizes PZR level at 35 gpm. At 650 gpm, leak exceeds makeup capability — trip reactor and actuate SI. SGTR-1 isolation: close 23AF21, 23AF11 (feed), 23MS167, 23MS18, 23MS7, 23GB4 (steam), trip 23 AFW pump, dispatch to close 23MS45, close 2SS333. Set 23MS10 to 1045 psig. Target cooldown temp from Table B: SG press > 1000 psig = 503 F CETs.
Exam — 2020 Q10
Restoring feed to a dry SG (EOP-FRHS-1): when CETs are stable or lowering, feed flow to ONE SG is limited to 1E04 to 5E04 lbm/hr (25-100 gpm) to prevent thermal shocking SG tubes. Per bases: feedwater flow rate limited to minimize excessive thermal stresses since a direct measure of SG temperature is not available. The thermal shock concern is the SG tubes, NOT the reactor pressure vessel. Remaining dry SGs may only be recovered at TSC direction.
Scenario — 2020 #4
21 SG tube rupture (650 gpm ramped over 5 minutes). Diagnostic indications: RCS pressure and PZR level lowering, 2R15 condenser off-gas rad monitor in alarm (OHA A-6). SGTR-1 isolation of 21 SG: close 21AF21, 21AF11 (feed — CT-18 Part 1), close 21MS167 (steam — CT-18 Part 2), 21MS18, 21MS7, 21GB4 already closed. Set 21MS10 to 1045 psig. Trip 23 AFW pump, lower speed to minimum first. Dispatch to close 21MS45 and 2SS321. Target cooldown temp from Table B: SG press >1000 psig = 503 F CETs.
Scenario — 2018 #1
24 SG tube rupture (650 gpm) occurs after reactor trip from RCP seal failure. Diagnostic indications: OHA A-6 RMS TRBL, 2R53D and 2R15 in alarm, followed by 2R41 and 2R19D. Manual SI initiated, re-enter EOP-TRIP-1. RO reports 24BF13 (FW isolation valve) failed to close on SI/Phase A — PO manually closes from console. 24 SG NR level rising uncontrolled → transition to EOP-SGTR-1. Isolation: close 24MS10 (set at 1045 psig), 24MS167, 24MS18, 24MS7, 24GB4. Close 24AF21 and 24AF11. Dispatch to close 24SG (2SS339). Shift gland sealing steam to alternate IAW S2.OP-SO.GS-0001. RCS cooldown target from Table B: SG press >1000 psig = 503 F CETs (CT#2).
Exam — 2019 Q53
SG shrink/swell on RCP shaft shear: when 13 RCP shaft shears at 25% power, steam flow from 13 SG lowers significantly (reduced RCS flow through the SG tubes means less heat transfer to the secondary). The reduction in steam production causes 13 SG NR Level to initially SHRINK (reduced voiding in the SG → apparent level drop). Trap: swell occurs when steam flow INCREASES (e.g., turbine trip reduces steam demand → pressure rise → less boiling initially, but more commonly steam flow increase causes more voiding). In this case, steam flow DECREASES, causing shrink.

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