U2 Main Turbine Cooling/SS/LO

Question 1

What are the U2 MT Trips?

Answer 1

Hardwire Trips

• Reactor Trip
• AMSAC (activated at > 40% pwr, auctates at < 25% FW flow 3/4)
• SI
• Overall HEA
• Unit HEA
• IOPS 110%
• Loss of SCW (10 second delay)
  - Low Pressure 28 #
  - Low Flow 666 gpm
  - High Temp 95°C (+ 5 second delay)
• Thrust Bearing Wear Abnormal > 32 mils (axial)
• P14 (SG Hi Hi Lvl at 67% 2/3 on 1 SG)
• Manual

PLC Trips
- Low EHC # 1100#
- EHC 2/3 < 800# 
- Overspeed 107%
Low Bearing Oil # < 14.7# for 5 sec **
- Low Condenser Vacuum ≤ 20.3" Hg 
- Loss of both DCS Pwr supplies

Question 2

What are the U2 Main Turbine Vibration alarms and auto trip?

Answer 2

• High High 12 mils (alarm)
• High 7-10 mils (alarm)
  - Manual trip at 12 mils > 1100 rpm and 22 mils < 1100 rpm
  - Auto trip on thrust 32 mils

Question 3

When does the U2 Turning gear auto start?

Answer 3

• 1 min after Main Turbine Trip.

- Engages when Main Turbine speed < 40 rpm.

Question 4

What are the U2 Turning Gear interlocks?

Answer 4

- Seal Oil ΔP > 7#
One of three bearing oil pumps on:
   - Auxiliary Lube Oil Pump
   - East DC Lube Oil Pump
   - West DC Lube Oil Pump
- Lift pump inlet # > 5 # 
- All Lift Pumps operating
 (If they are the Bypass Interlock Available for Lift Pumps, must be held)

Question 5

When does 2-CMO-40 (Exhaust hood spray) open?

Answer 5

• Generator Load < 7.5%
• Turbine Speed > 900 rpm
• Manual

Question 6

What does the Main Turbine Thrust Bearing do?

Answer 6

• Limits Axial Movement to prevent stationary and rotating blade contact

Question 7

When does the AC Lube Oil pump supply oil to the U2 Main Turbine?

Answer 7

• Turbine speed < 1800 rpm

Question 8

When does the AC Lube Oil pump auto start for the U2 Main Turbine?

Answer 8

• Turbine Trip

- Low Lube Oil # at 16#

Question 9

When do the 2 DC Lube Oil pumps auto start for the U2 Main Turbine?

Answer 9

• Turbine Trip

- Low Lube Oil # at 16#

Question 10

When do the 2 DC Lube Oil pumps supply oil to the U2 Main Turbine?

Answer 10

• supplies bearing oil when the Shaft Driven LO Pump or Aux Oil Pump fail

Question 11

What does LRV-32, LO supply header # Reg Valve, do?

Answer 11

• Maintains U2 turbine supply header # at 24.5# by dumping excess pressure back to the lube oil tank

Question 12

What do the reheat stop and intercept valves do?

Answer 12

• Both Close on Main Turbine Trip to minimize the potential for overspeed of Main Turbine
• Intercept valves throttle to limit overspeed on a load rejection to prevent a turbine trip

Question 13

How do the SRV-26/27, aux steam supply valves fail on U2?

Answer 13

• Fail as is

Question 14

What does SRV-12 (U2 MS Bypass Header supply to steam seals) do?

Answer 14

• keeps HPT Inner Steam Seals 10# > HPT exhaust during normal operation. SRV-12 feeds into a separator tank prior to entering HPT inner seals

Question 15

What supplies LPT Steam Seals during normal operation?

Answer 15

• HP inner seals supply most of steam for seal stm header after it exits the HPT
• Can receive some steam from HP and LP Stop and Ctrl valve leakoff,
• and some aux steam as necessary when HP and LP stop and ctrl valves are backseated

Question 16

What supplies Steam Seals during startup, shutdown and low power operation?

Answer 16

• 50# aux steam supplies steam seals through SRV-22 and SRV-26/27

Question 17

What dumps excess steam pressure for the steam seals on U2?

Answer 17

• SRV-25 (Steam Seal Dump Valve) controls pressure and dumps extra steam to 2A/2B Heaters

Question 18

How does SRV-22 (Aux Steam reg supply valve) fail on loss of air?

Answer 18

• Fails open

Question 19

How does SRV-25 (Seal disch to 2A/B heaters) fail on loss of air?

Answer 19

• fails closed

Question 20

When do the U2 bearing lift pumps auto start?

Answer 20

• Turbine Trip

Question 21

Where in the Lube Oil Flowstream does the DC Emergency Lube Oil Pump discharge?

Answer 21

• Discharge after the Lube Oil Coolers (bypasses them)

Question 22

What effect will long term operation on the DC Emergency Lube Oil pump have?

Answer 22

• Long term operation will cause higher LO temps

Question 23

The Unit 2 High Pressure Turbine inner steam seal is supplied with Main Steam which normally is controlled ____ psi greater than turbine exhaust pressure.

Answer 23

• 10#

Question 24

How do we prevent the MT from tripping on a Rx trip?

Answer 24

• Knife switches are opened to allow turbine to stay on grid when Rx is tripped (prevents turbine overspeed)

Question 25

How do you adjust the Gland Steam Condenser fan?

Answer 25

• adjust blower suction inlet orifice plate (sliding damper) position to 10” vacuum on the Gland Steam Condenser

Question 26

What supplies steam during turbine startup?

Answer 26

• Intermediate header
  Aux steam
• High # header
  Main steam

Question 27

If you lose the glad steam condenser fan, what will happen?

Answer 27

• Steam will leak out turbine and MPF to atmosphere