Extraction steam and Drain System

Question 1

What is the purpose of the ED system?

Answer 1

Preheats condensate and feedwater prior to entering the steam generators to increase overall plant efficiency

Question 2

What system has the ability to provide steam to the 4th point heater during startup?

Answer 2

Aux steam

Question 3

What system is used to add cool water to the water volume that is maintained in the bottom of the blowdown stack?

Answer 3

DS domestic service

Question 4

What is the purpose of the blow down stack?

Answer 4

A collection point for steam traps, HP heater relief valves and Misc aux steam drains

Question 5

When is DS added to the blowdown stack? What if DS is not available?

Answer 5

When temp of the blowdown stack exceeds 150F

If not available there will be steam coming out of the blowdown stack and the north condenser sump

Question 6

how does GA interact with ED?

Answer 6

Supplies nitrogen for steam blanketing when shut down to prevent corrosion

Question 7

How does IA interact with ED?

Answer 7

MT control system admits IA thru both critical and non critical relay dump valves which provide a signal to the bleeder trip valves

Also provides motive force for all AOVs in ED system

Question 8

how are the BTVs affected by a loss of IA?

Answer 8

They lose open permissive and go partially closed. They stay open due to ED steam flow

Question 9

Where are the Heater drain pumps powered from?

Answer 9

‘A’ NBN-S02 AND ‘B’ NBN-S01

Question 10

Where does the seal water for each heater drain pump come from?

Answer 10

Directly from the condensate header at 375-500 psig

Question 11

What provides cooling to each heater drain pump stuffing box?

Answer 11

Condensate service header at 50-100psig

Question 12

What positions the heater drain pump mini flow valves?

Answer 12

Heater drain pump flow transmitter

Question 13

What 3 signals would stop the heater drain pump?

Answer 13

Heater drain tank lo-lo level
Heater drain pump low flow after a time delay
Electrical protection signal

Question 14

Why does the #5 heater not have a level control system?

Answer 14

It drains directly to the heater drain tank and does not have a drain cooler region

Question 15

Which LPFW heaters have 4 inlets?

Answer 15

1 and 2

Question 16

which LPFW heater has an input from the S/G blowdown system?

Answer 16

3

Question 17

What is the purpose of the BTVs?

Answer 17

To prevent reverse steam flow when the turbine trips and prevent turbine overspeed

Question 18

What is installed on the BTVs to assist in opening the disc with a minimum differential steam pressure?

Answer 18

Balance arm device

Question 19

What happens upon activation of the BTV test valve?

Answer 19

Valve equalizes the air pressure across the operator piston to allow partial closing of the valve disc by spring force

Question 20

why is there 2 BTVs on the #4 LPFW heater?

Answer 20

4 has enough energy to overspeed the turbine

Question 21

Which control valves are reverse acting?

Answer 21

All the valves that dump to the condenser (all high levels and #1 LPFW heater normal)

Question 22

what air pressure are the reverse acting valves full open and full closed?

Answer 22

Full open at 3psig
Full closed at 15psig

(Normals) full closed 3 psig and full open 15psig

Question 23

What happens upon a hi-hi signal in a HP heater?

Answer 23

Extraction steam isolated

Close the normal level control valves of the preceding heater

opens the affected heaters motor operated extraction steam drain line

The 1st and 2nd stage drain tanks will vent to the condenser also

Question 24

What power level may there be insufficient D/P between the heater shells to allow for proper operation of the normal level control valves?

Answer 24

20%

Question 25

When is the first heater drain pump started?

Answer 25

25% power

Question 26

when is the 2nd heater drain pump started?

Answer 26

30-40%

Question 27

During plant shutdown when are the heater drain pumps secured?

Answer 27

First one at 40% and the second at 25%

Question 28

How is the ED system affected by loss of IA?

Answer 28

Heater drain pump discharge valve fails closed, recirc valve fails open, putting the pump on recirc.

Heater drain tank, MSR drain tank and 1st and 2nd stage reheater drain tank and feedwater heater high level dump valves all fail open and the normals fail closed except for the #1 heater

Heater drain pump will eventually trip on low flow or heater drain tank lo lo signals

The main steam supply to the 2nd stage reheater will isolate and the 1st and 2nd stage reheater drain tanks and tube bundles will vent to the condenser instead of their respective feedwater heaters