.AR SG-Main Steam (Welch's Highlighted Notes)

Question 1

Steam Generators:

• Transfer ~ ? MWt from…
• ?
• Feedwater ring
  
  • ?
• Economizer: Located?

Answer 1

Steam Generators:

• Transfer ~ 4013 MWt from RCS to the secondary. Design: 575°F / 1270 psia
• No load: ~1170 psia, 100%: ~1040 psia
• 18.0 x 10⁶ lbm/hr of 1030 psia saturated steam when feedwater is 450°F. Moisture content limited to 0.1%
• Outlet nozzle flow orifice - limits steam flow in the event of a SLR (steam line rupture) (↓ peak CTMT pressure, ↓ CDR, ↓ + reactivity addition rate)
• Feedwater ring:
  
  • Distributes feedwater from the downcomer feedwater nozzle. Supplies water into the downcomer region.
  • Used during emergency conditions to prevent thermally shocking the U-tubes.
• Economizer: Located just above the tube sheet on the cold leg side. Increases efficiency by preheating incoming feedwater before it enters the evaporator section. (Normal feed line)

Question 2

MSIVs (SG1 – 170/180, SG2 – 171/181):

• ?

Rapid positioning:

• ?

Slow positioning:

• ?

Power supplies (125Vdc):

• ?

Controls:

• ?

Answer 2

MSIVs (SG1 – 170/180, SG2 – 171/181):

• 140’ MSSS. Hydraulic-actuated, double-disc, wedge valves.
  
  • Do not open > 100 psid

Rapid positioning:

• Uses accumulator pressure to close
• < 4.6 seconds on MSIS

Slow positioning:

• Used to open, close, and “exercise“ the valves (close to 90%)
• ~ 5 minutes to open
• Uses air operated hydraulic pump

Power supplies (125Vdc):

• Normal: directly from the battery (PKA or PKB).
• Back-up: from the bus (PKA or PKB).
• Selected by closing breakers on the PK bus.

Controls:

• Each valve has two slow positioning HSs (Train A and B)
• Each SG has two fast close PBs (Train A and B)
  
  • Closes BOTH valves from a SG
  • Pushing both (on one SG) will discharge both train accumulators & render them inoperable.
• Loss of power: fails closed.
• Loss of IA only: does not change position, remains capable of Fast Closing with air reservoir.
• Loss of IA and air reservoir: fails as is, cannot fast close

Question 3

MSIVs (SG1 – 170/180, SG2 – 171/181):

MSIV’s hydraulic supply system:

• Purpose/Design?
• Accumulators (2):
  
  • ?
• Air reservoirs (2):
  
  • ?

Single MSIV Closure (40AL-9RK6A):

• ?

Answer 3

MSIVs (SG1 – 170/180, SG2 – 171/181):

MSIV’s hydraulic supply system:

• Each MSIV has independent, self-contained hydraulic actuator and two redundant hydraulic supply systems.
  
  • Pump: Only common component to both hydraulic systems. Pneumatic (air) operated PDP.
• Accumulators (2):
  
  • Stores pressurized hydraulic fluid for quick closing.
  • Pre-charged with nitrogen, then filled to the desired level and pressure (5200 psig) using the hydraulic pump.
    
    • 5000 psig – minimum Tech Spec pressure
    • 5400 psig – upper limit to protect seals
  • Pressure indicated in MCR / ERFDADS
  • Relief valve kept isolated.
  • Manually bleed off pressure if needed.
• Air reservoirs (2):
  
  • Backup control air supply for positioning the hydraulic fluid control valves.
  • Ensures MSIV’s can be closed following the loss of off-site power and air.
  • SEIS alarm on low pressure (74 psig).

Single MSIV Closure (40AL-9RK6A):

• Reduce power to < 65%.
• Place DFWCS in 1E.
• Re-open with 40OP-9SG01 (Slow Open).

Question 4

Economizer Isolation Valves (SG1 132/174, SG2 137/177):

• ?

Answer 4

Economizer Isolation Valves (SG1 132/174, SG2 137/177):

• Electro-hydraulically operated.
• 2 valves in series on each feed line.
• MSIS auto closure (Closes associated train valves)
• Similar to MSIVs except the actuator only has a single hydraulic control system train with two accumulators.
• Each FWIVs only closes on associated train MSIS signal.

Question 5

Exercise/Test switches (MSIVs/FWIVs):

• Exercise: ?
• ACC CH TEST: ?

Answer 5

Exercise/Test switches (MSIVs/FWIVs):

• Exercise: valve will slow close using hydraulic pump discharge. At 90%, limit switch causes it to slow open.
• ACC CH TEST: actuator system is lined up to discharge the associated accumulator to the hydraulic reservoir so that the accumulator N2 pre-charge pressure can be checked without causing valve movement.

Question 6

MSIV Bypass Valves (1 per SG):

• ?

Answer 6

MSIV Bypass Valves (1 per SG):

• Close in < 4.6 seconds against 1400 psid.
• MSIS auto closure (either train will close both bypass)
• Train A and B SOVs in series in its air supply. Both energized to open the MSIV bypass.
• AOVs: Fail closed (loss of air / PK power).
  
  • Closed by spring pressure.

Question 7

Main Steam Safety Valves:

• 5 per steam line (setpoint A/L 1%, A/F 3% per Tech Spec bases)
  
  • 1^st – # psig ?
  • 2^nd – # psig ?
  • 3-5^th – # psig ?
• ?

Answer 7

Main Steam Safety Valves:

• 5 per steam line (setpoint A/L 1%, A/F 3% per Tech Spec bases)
  
  • 1^st – 1250 psig
  • 2^nd – 1290 psig
  • 3-5^th – 1315 psig
  • 1% accumulation and 3% blowdown
• MCR Indications (acoustics, powered from NNN-D11):
  
  • 1 green light (valve closed) / 1 red light (9% open) / 1 red light (100% open)

Question 8

Atmospheric Dump Valves (SG1 178/184, SG2 179/185):

• Operated from …?
• Operated with:
  
  • ?
  • ?
  • ?
• ADVs fail…?
• N2 accumulators for ADVs:
  
  • ?

Answer 8

Atmospheric Dump Valves (SG1 178/184, SG2 179/185):

• Operated from MCR, RSP or locally:
  
  • MCR Controllers powered from PNA/PNB (120Vac)
    
    • Loss of PNA or PNB – two ADVs failed closed
  • “CR” push-button at RSP must be depressed for MCR control.
    
    • MCR alarm if not in “CR”
  • ADV permissive hand switches - both in OPEN PERMISSIVE to allow remote operations.
  • Permissive circuits powered from PKA, PKB, PKC or PKD.
    
    • Each power supply supplies two switches, impacting two ADVs. (loss of any PK – two ADVs failed closed)
  • Loss and restoration of 120Vac, the LOCAL/CR output module will be forced into “CR”
  • Blown fuse causes green lights to be dimly lit.
• Operated with:
  
  • Instrument Air
  • N2 from Service Gas (HP N2)
  • N2 accumulators
• ADVs fail closed (loss of air and N2 OR loss of power)
• N2 accumulators for ADVs:
  
  • Automatically aligned if instrument air is < 100 psig
    
    • SOV energized to open and align N2
  • N2 < 615 psig: ADV is inoperable (TSR 3.7.200.1)
  • 184 & 185 – each supplied by a pair of 28 ft³ accumulators
  • 178 & 179 – each supplied by one 56 ft³ accumulator
  • Design: ADV operation (assuming N2 > 615 psig) for either:
    
    • 16 hour SBO coping time
    • 4 hours in M3 and 9.3 hours to align SDC (LCO bases)
• 30% controller output required to start opening the ADV (overcomes bonnet pressure)
• Closing ADV Inlet Isolation Valve with the ADV partially open will damage the Inlet Isolation Valve
• ADVs can be locally operated with a hand wheel (isolate IA/N2, open equalizing valve, engage the clevis)

Question 9

Downcomer Isolation Valves (SG1 130/172, SG2 135/175):

• MSIS…?
• Pneumatically-operated by …?
• Back-up N2 accumulator:?
• Loss of power (PK): ?

Loss of all pneumatic pressure (air, N2, & accumulator): ?

Answer 9

Downcomer Isolation Valves (SG1 130/172, SG2 135/175):

• MSIS auto closure (Closes associated train valves)
• Pneumatically-operated by N2
• IA repositions the pneumatic servo to align for opening or closing.
  
  • N2 is also the back-up supply to servos
• Back-up N2 accumulator: provides 8 hours of valve operation if air is lost
  
  • 1 tank for all 4 valves
  • N2 accumulator automatically aligned by energized to open SOV if HP N2 pressure is low
  • Low N2 pressure (550 psig) – MCR alarm
    
    • Analyzed to operate at 235 psig.
    • Valves drifts closed at 150 psig.
  • Allows AFN pump to supply the SGs.
• Loss of power (PK): fail OPEN (allows AFN to feed SGs)
• Loss of all pneumatic pressure (air, N2, & accumulator): fail closed

Question 10

Main Steam Isolation Signal (MSIS):

• ?

Isolates:

• ?

Answer 10

Main Steam Isolation Signal (MSIS):

• Low SG pressure (< 960 psia – variable)
• High CTMT pressure (> 3 psig NR)
• High SGWL (> 91% NR level)

Isolates:

• Downcomer FWIVs
• Economizer FWIVs
• MSIVs (MSIVs close on either train of MSIS)
• MSIV Bypasses (Closes on either train MSIS)
• Upstream Steam Trap Isolation Valves
• SGBD CIVs (AOVs) and SG sample CIVs (SOVs)

Question 11

Steam Traps:

Upstream MSIV Traps (6)

• ?

Downstream MSIV traps:

• ?

Each isolation valve has a steam trap in parallel with it.

• ?

Answer 11

Steam Traps:

Upstream MSIV Traps (6):

• MSIS auto isolation
• AOVs Fail closed (loss of air or power)
• 1 per MSIV / 1 per AFA supply

Downstream MSIV traps:

• Eight traps (2-inch drain lines)
• MOV isolations
• No auto closure

Each isolation valve has a steam trap in parallel with it.

• Normally open during turbine synch and closed at power.

Question 12

Instrumentation (SG-Main Steam System):

RU-142A-D MS Line N-16 Monitors:

• ?

Answer 12

Instrumentation:

RU-142A-D MS Line N-16 Monitors:

• Ch 1&2 – SG1 / Ch 3&4 – SG2
• One per steam line. (140’ Turb Bldg / next to each other)
• Alarm: detects 30 GPD leak in area of highest susceptibility (upper hot side tube bundle)
• Tube leak: all ↑ due to proximity of RUs
  
  • affected SG RUs ↑ higher
• Indication will ↓ with reactor power (N-16↓)
• Alarm on change in leak rate (“Urgent” alarm)

Question 13

Instrumentation (SG-Main Steam System):

TRM TLCO 3.3.101 Rad Monitoring

• ?

Answer 13

Instrumentation (SG-Main Steam System):

TRM TLCO 3.3.101 Rad Monitoring

• MSL RMs functional in Modes 1-4.
• 1 channel (A or B) required per SG.
• RU-139 A & B / RU-140 A & B.
• Setpoint: 3 x background
• If not met, restore or establish alternate monitoring in 72 hours (alternate is per the REP)
• Located next to steam lines upstream of ADVs and safeties in the MSSS. Monitors effluent doses.
• Used for SGTR diagnosis.
• May only detect > 10-15 gpm tube leak under normal failed fuel conditions at 100% power.
• Response is proportional to reactor power (N-16 detectors)
• Post trip, may not see the leak unless major fuel damage.
• Manually isolate associated SGBD if in High alarm (ARP)

Question 14

Instrumentation (SG-Main Steam System):

S/G Levels

• 2 NR LTs per SG
  
  • ?
• 4 WR LTs per SG (class)
  
  • ?
• 4 NR LTs per SG (class)
  
  • ?
• Normal operating level: ?
• Post trip (mode 3): ?
• 60% WR correlates to 0% NR.
  
  • ?
• Top of U-tubes (~?% NR) [per EOP Set point calcs]

Answer 14

Instrumentation (SG-Main Steam System):

S/G Levels:

• 2 NR LTs per SG
  
  • SG1: LT-1111, 1112, SG2: LT-1121, 1122
  • FWCS, ERFDADS, Plant Computer, indication and annunciators.
• 4 WR LTs per SG (class)
  
  • SG1: LT-1113A-D, SG2: LT-1123A-D
  • PPS, Plant Computer, QSPDS (A & B), indication & RSPs (A & B trains).
• 4 NR LTs per SG (class)
  
  • SG1: LT-1114A-D, SG2: LT-1124A-D
  • PPS, Plant Computer, ERFDADS and indication.
• Normal operating level: 80% WR (~ 47% NR).
• Post trip (mode 3): 45-55% NR
• 60% WR correlates to 0% NR.
  
  • NR (150” span, 0% is 369” above tube sheet)
  • WR (376.25” span, 0% is 143” above tube sheet)
  • Share upper tap at 55.5” above moisture separator support plate.
• Top of U-tubes (~24% NR) [per EOP Set point calcs]

Question 15

Instrumentation (SG-Main Steam System):

Steam Pressures:

• ?

PAM (LCO 3.3.10) and RSP (LCO 3.3.11) – Modes 1-3:

• ?

Answer 15

Instrumentation (SG-Main Steam System):

Steam Pressures:

• SG ∆P (between SG1 and SG2 for AFAS ∆P lockout) (A,B,C,D)
• SG1 Pressure and SG1 VSP (variable setpoint) (A,B,C,D)
• SG2 Pressure and SG2 VSP (variable setpoint) (A,B,C,D)
• Main Steam Common Header Pressure (PT-1024/1027, 900-1300 psia) (SBCS/COLSS)
• 2 SFs per SG, 1 per steam line (DFWCS/SBCS/COLSS)

PAM (LCO 3.3.10) and RSP (LCO 3.3.11) – Modes 1-3:

• 2 WR LT (0-100%) per SG
• 2 WR PT (0-1524 psia) per SG

Question 16

LCO 3.7.1 Main Steam Safety Valves (MSSVs) [Modes 1-3]:

• ?

Answer 16

LCO 3.7.1 Main Steam Safety Valves (MSSVs) [Modes 1-3]:

• Mode 1 & 2: 10 per SG required
  
  • Up to 4 on any SG can be inoperable (↓ power per table within 4 hrs / ↓ VOPT setpoint within 36 hrs)
  • If 5-8 inoperable on any SG, Mode 3 in 6 hours
• Mode 3: 2 per SG required
• Operable: open within setpoint band, relieves overpressure, and re-seats.
• As-found ± 3% setpoint. As-left ± 1% setpoint.
• Limit secondary pressure to ­≤ 110% of design when passing 100% of design steam flow.
• Secondary pressure limiting event: Full power Loss of Condenser Vacuum (LOCV).
  
  • Determines the max allowed thermal power with inoperable MSSVs
• Primary pressure limiting event: Full power FWLB in CTMT, with failure of the backflow check valve in the FW line.
• MODE 3: one MSSV per SG (two total) has sufficient relieving capacity to dissipate core decay heat and RCP heat to limit secondary system pressure to ≤ 110% of design pressure. (2 per SG required for redundancy)

Question 17

LCO 3.7.2 Main Steam Isolation Valves (MSIVs):

• ?

Answer 17

LCO 3.7.2 Main Steam Isolation Valves (MSIVs):

• Four MSIVs and associated actuator trains required to be operable.
• Modes 1-4 except when all MSIVs are closed and deactivated.
• One MSIV with 1 act train INOP - restore actuator in 7 days OR declare MSIV inoperable.
• Two MSIVs with 1 act train (different trains) INOP - restore one in 72 hours OR declare MSIVs inoperable
• Two MSIVs with 1 act train (same train) INOP - restore one in 48 hours OR declare MSIVs inoperable
• Two actuators on 1 MSIV INOP - immediately declare the MSIV inoperable
• ≥ 3 actuators inoperable - immediately declare affected MSIVs inoperable
• One MSIV inoperable in Mode 1 - restore in 4 hours or RICT. Be in Mode 2 within 6 hours if not met.
• > 1 MSIV inoperable in Mode 1 – restore in 1 hour or RICT. Be in Mode 2 within 6 hours if not met. (cannot voluntarily enter RICT)
• ≥ 1 MSIV inoperable in Modes 2-4 - close the MSIV in 4 hours, verify closed every 7 days OR go to Mode 5.
• Isolation times (3.8 sec per ST) are within limits and auto close on MSIS.
• Actuator train operability: capable of fast-closing on demand and within time limit. > 5000 psig in accumulator.
• Adequate air pressure to support fast-closure (SEIS alarm ≤ 74 psig on air reservoir).

Question 18

LCO 3.7.3 Main Feedwater Isolation Valves (MFIVs):

• ?

Answer 18

LCO 3.7.3 Main Feedwater Isolation Valves (MFIVs):

• Four economizer and four downcomer MFIVs operable
• Modes 1-4 except when MFIV is closed and deactivated or isolated by a closed and deactivated power operated valve.
• Any FWIV inoperable: close/isolate in 72 hours or RICT. Verify every 7 days
• Two FWIVs inoperable on same flow path: isolate path in 8 hours or RICT. Verify every 7 days.
• Isolation times within limits and auto close on MSIS.
• Isolates feed water to the SGs (FWLB/SLB/SG overfill)
  
  • Limits RCS cooldown
  • Limits mass added to CTMT (break in CTMT)
  • Isolates non-safety related portions of MFW system
  • Prevent water from entering steam lines (overfill)

Question 19

LCO 3.7.4 Atmospheric Dump Valves (ADVs):

• ?

Answer 19

LCO 3.7.4 Atmospheric Dump Valves (ADVs):

• Four ADVs operable in Modes 1-4 when SG is being relied upon for DHR.
• One ADV inop on one or both SGs – 7 days or RICT
• Two ADVs inop on one or both SGs – 24 hours or RICT (all 4 could be inoperable, cannot voluntarily enter when intentionally making the last ADV inoperable)
  
  • Operable: capable of providing a controlled relief of steam flow and capable of fully opening and closing on demand.
  • Local hand wheel not credited/not required
  • Required to have a nitrogen supply that supports ADV operation for 13.3 hours (≥ 615 psig per TRM).
  • Capable of cooling the unit to SDC entry conditions.
  • Primary success path for RCS cooldown during a SGTR to minimize off-site dose.

Question 20

TRM TLCO 3.7.200 Atmospheric Dump Valves (ADVs):

• ?

Answer 20

TRM TLCO 3.7.200 Atmospheric Dump Valves (ADVs):

• N2 accumulator tank ≥ 615 psig. If not met, immediately declare ADV inoperable
• Sufficient N2 to operate ADVs for 4 hours at hot standby plus 9.3 hours of operation to reach M5 on natural circulation and loss of normal control air system fails.

Question 21

LCO 3.7.16 Secondary Specific Activity:

• ?

Answer 21

LCO 3.7.16 Secondary Specific Activity:

• ≤­ 0.10 μCi/gm DE I-131. Modes 1 – 4.
• If not met, M3 in 6 hours, M5 in 36 hours.
• Assumption in MSLB analysis (LOOP, use of ADV). Small fraction of dose limits.

Question 22

TRM TLCO 3.7.100 SG P/T Limits:

• ?

Answer 22

TRM TLCO 3.7.100 SG P/T Limits:

• SG temp > 70°F if SG pressure is > 650 psig.
• If not met, ↓ pressure to ≤ 650 psig in 30 min and perform engineering evaluation.