Exam 4

Question 1

Turbine Runbacks and Setbacks

• OTΔT/OPΔT runback
• SCW Runback
• Vacuum Runback
• SGFPT Trip runback
• Circ Water setback

Answer 1

• 133%/min for 2.3 secs, waits 27.7 seconds
• 133%/min for 4 seconds, waits 17 seconds
  
  • 82°C on 2/3
  • Low inlet flow for amps (81%)
• Starts at 5.5” and ramps from 1%/min to 4%/min as vacuum degrades from 5.5 to 6.5” HgA linearly.
  
  • Will not disable until vacuum is < 5.4” HgA or if Intermediate Power < 40%
• 5%/min to 54.4% value control set.
• Trip of CW Pump (when enabled) and vacuum rises to > 5” HgA.
  
  • 12 MWe/sec (~1%) to 75% Rx Power (60% valve control set)

Question 2

Turbine Lube Oil Operation from 0 to 1800 RPM

• Initial Alignment
• Sequence as speed rises

Answer 2

• TGOP supplying bearings, MSP supplying suction to SLO pump. All lift oil pumps running, ESLO pump in standby.
• As speed ↑, SLO discharge pressure ↑
  
  • @75% speed (1350 rpm), Low LO discharge trip enables (100 psig on 2/3)
  • @90% booster pump sufficient to maintain SLO suction
  • TGOP & MSP back checked, must be manually secured
    
    • Lift oil pumps automatically secure when TGOP < 5 psig.

Question 3

Main Turbine Lube Oil

• Normal shaft LO pump discharge pressure
• Normal Supply pressure from booster pump
• Normal bearing supply header pressure
• Low SLO pump discharge turbine trip setpoint
• Low bearing header pressure turbine trip setpoint
• Special feature of booster baffler valve
• Reservoir Hi/Lo alarms
• Lube Oil Cooler temp band & cooling
  
  • Minimum to start pumps, lift pumps, roll turbine.
  • Normal bearing temp, Max bearing outlet, and Max ΔT across bearing

Answer 3

• 200-235 psig
• 35 psig
• 25 psig
• 100 psig on 2/3 when > 1350 rpm
• 12 psig on 2/3
• Drilled hole allows ~ 60% of flow if valve closes
• ±4” from reference level (36”)
• 100-120°F by service water
  
  • 50°F, 80°-90°F, 90°
  • 140°-160°F, 180°F, 50°F

Question 4

Turbine Lube Oil Pump Features

• Auto Start features of:
  
  • Motor Suction Pump
  • Turning Gear Oil Pump
  • Emergency Bearing Oil Pump
  • Lift Oil Pumps
    
    • How many, which bearings, when should it be operating, how to arm, what the green/yellow warning lights mean
  • Turning Gear

Answer 4

• SLO suction pressure < 10 psig Shaft Pump Suction
• SLO discharge < 190 psig Shaft Pump Discharge OR bearing header < 15 psig
• SLO discharge < 180 psig Shaft Pump Discharge AND TGOP discharge pressure < 10 psig
• Armed AND bearing header > 2 psig AND TGOP pressure > 10 psig.
  
  • 8 pumps, supply bearings 3-10 (1 brg/pump); pumps 8 & 9 use same HIS on MCB; Anytime < 900 rpm & everytime turning gear operating, HIS in stop & Press local arm PB; yellow < 840 psig green < 265 psig
• Bearing header > 15 psig
  
  • At least one lift oil pump operable.
  • Turbine < 200 rpm by speed sensor
  • Turbine stopped by low speed sensor
  • V53 & V55 open
  • Auto Starts when shaft reaches 0 RPM as long as permissives are met.

Question 5

MSR Operation

• Startup
  
  • When to open 1st stage MOV
  • When to open 2nd stage MOV Bypass
  • Sequence of event to operate 2nd stage reheat
• Shutdown
  
  • Operation of 2nd stage reheat
  • Operation of dumps

Answer 5

• Startup
  
  • Manually open MSR 1st stage MOV @ 1800 rpm
  • Manually open MSR 2nd stage MOV Bypass during Chest warming.
  • Manually open Source MOVs prior to grid synchronization.
    
    • at ~10% intermediate power, 1st stage drains dump
    • At ~20, 2nd stage drains dump
    • From 15-65% Low Load valves modulate open
    • At 67% High Load Valves open.
• Shutdown
  
  • At 65% High Loads Close
  • At ~18% all 2nd stage drains dump
  • At 15% all low load AOVs are closed
  • At 8% all 1st stage dumps open

Question 6

Steam Seals and Exhaust

• Sources of steam sealing
• Normal pressure range
• Operation of unloader valve
• Transition between controllers as power rises
• System reliefs

Answer 6

• Sources: Main Steam, Aux Steam, 12th stage from LP ‘A’, HP turbine glands, SV leakoff, CV leakoff.
• Normal: 2.5-5 psig
• Unloader dumps to condenser starting at 4 psig, full open at 7.5 psig.
• As 12th stage pressure ↑, MS Supply closes. At ~50% load, all sealing steam is from extraction extraction (in theory). In reality, leakoff from HP turbine and/or SVs or CVs maintains the system at high power.
• 3 heater reliefs @ 20 psig, 1 near controllers @ 120 psig. Relieve outside of the East side of TB.

Question 7

Combined Intercept Valves

• How each are opened
• How they operate on overspeed? Trip?
• Which CIVs are paired (master-slave)?
  
  • Interlock between paired CIVs

FSAR Chapter 16, 16.3.4 Turbine Overspeed Protection Requirements

Answer 7

• ISV opens when turbine reset, IV opens when RPM selected on HMI.
• On overspeed master valve shuts linearly from 105-107% overspeed. When master is 50% shut, slave shuts.
  
  • CIV 1 → 4, 2 → 6, 3 → 5 (first valve is master, second is slave)

At least one O/S system shall be functional in Modes 1-3, consists of SVs, CVs, & CIVs & Extraction non-return valves.

Question 8

Shell and Chest Warming

• HUR limits of: LP turbines, MSRs, Stm Chest, and 1st stage shell
• Flow path for Shell warming & target
• Flow path for Chest warming & target
• Which to do first?

Answer 8

• LP tubines & MSRs 125°F/hr, chest and 1st stage shell 150°F/hr
• Thru #2 SV, CVs open into HP turbine, CIVs closed Target 250-275°F
• Thru #2 SV, CVs closed.
• Always shell first IVs closed, ISVs open, 460°F

Question 9

Seal Oil System

• Normal pressure
• Purpose of recric pump & vacuum pump
• Emerg. Oil pump stepoint
• Purpose of float trap
• When seal oil can be secured
• How is H₂ removed from oil
• H₂ press limit if seal oil system supplied by Turbine LO

Answer 9

• 8 psig above H₂ (78-83 psig). Procedure requires 7-11.5 psig > H₂ pressure.
• Recric pump removes entrained moisture & air
• 110 psig
• Maintains oil level in trap above oil/H₂ interface to prevent H₂ entry into air detraining section/bearing oil header.
  
  1. Shaft not rotating
  2. Turbine LO System is supplying > 20 psig @ turbine Centerline
  3. H₂ pressure < 17 psig
• H₂ exposed oil drains to H₂ detraining tank where the H₂ is vented to the float trap. H₂ from float trap is vented back to Generator.
• 17 psig

Question 10

Generator H₂ System

• Normal pressure, purity, max pressure
• Cooling
  
  • Max cooler outlet temp
  • H₂ explosive limits
  • Order of operations to vent H₂ or replace H₂

Answer 10

• 70-75 psig, 80 psig max, 95% purity
• Service Water cools via EA-TV-7
  
  • Turbine Load reduction if > 56°C
• H₂ in air between 4 & 75% explosive
• Purge H₂ with CO₂ then air to shutdown.
• Then Purge air with CO₂ then H₂ to Startup.

Question 11

Stator Cooling Water

• Operation of PCV
  
  • Mechanical stops. If PCV fails low, will there be a runback?
• SCW pump standby feature(s)
• Setpoint of TCV
• SCW runback(s)
• Turbine trip from runback circuit
• Manual turbine trip from SCW parameters

Answer 11

• PCV maintains 3 psig less than H₂ pressure (67-72 psig)
  
  • Mechanical stops keep flow 780-870 gpm.
    
    • Failure doesn’t lower flow enough to cause runback (~651 gpm)
• Standby starts @ 134 psig
• Maintains 40-45°C via service water (@ 40-50 psig)
• SCW Runbacks:
  
  • Stator Outlet >81°C on 2/3
  • Stator inlet flow <81% of the derived value based on Generator Amps
• If runback present, the turbine trips after:
  
  • 2 minutes if generator amps > 24,000
  • 3.5 minutes if generator amps > 6,976