Stator Water Cooling - 1.0

Question 1

Under what conditions will the Standby stator water pump start?

Answer 1

Low Discharge header pressure
Normal pressure switch setpoints - 107# sensed at the pump discharge and 69# sensed after the heat exchanger and filters. This is equivalent to 730 gpm flow
Backup pressure switch setpoints - 98# sensed at the pump discharge and 64# sensed after the heat exchanger and filters. This is equivalent to 690 gpm flow

Question 2

What is the power to the standby stator water pump auto starts?

Answer 2

Normal pressure switches - 10C120 DC control power
Backup pressure switch - AC Power that comes from the pumps power source

Question 3

What are the SWC pump trips?

Answer 3

Unit substation under voltage
Unit differential overcurrent
Generator neutral overcurrent
Generator differential overcurrent

Question 4

How do you reset the SWC pump trips and why is it important?

Answer 4

Must be reset locally in order to remove the tripped condition and run the SWC pumps

Question 5

What are the conditions that must be met for proper De-ionizer operation?

Answer 5

Inlet temp 122F (prevents resin breakdown)
Flow 100gpm (prevents channeling)

Question 6

What components does the SWC system supply and what are their respective flow rates?

Answer 6

811 gpm to stator bars
47 gpm to high voltage bushings (terminal)
100 gpm to deionizer

Question 7

Under what conditions will the the SWC system initiate a Turbine Generator and Recirc pump full runback and what is the required number of logic inputs?

Answer 7

2 of 3 logic
After a 15 sec time delay the following conditions will initiate the protective actions:
Low SWC Inlet Pressure – 64#
Hi SWC Outlet Temp – 79C
Low Flow – 690gpm

Question 8

What is expected sequence when a Turbine Generator and Recirc pump full runback occurs in response to a SWC system logic signal?

Answer 8

15 sec TD
EHC Load set to minimum - if the initiating
condition clears the turbine runback will stop
Additional 12 sec TD (@27 Secs)
Full Recirc runback to 30% occurs - once initiated
it is sealed in and must be manually reset

Question 9

If the main turbine runback is not successful in reducing armature current, under what conditions will the Digital EHC system automatically trip the turbine?

Answer 9

> 25 kA for 2 min
7055 A for 3.5 min

Question 10

What are the operator actions if SWC is lost and reactor power is >18%?

Answer 10

In 2 minutes the RO must:
REDUCE Recirc pump speed to minimum
LOCK the Mode Switch in Shutdown
Trip the Main Turbine

Question 11

What conditions could indicate stator water leak past the stator water-generator gas barrier and what actions should you take if it occurs?

Answer 11

If generator pressure drops below 63# you must remove SWC from service to prevent leakage onto the windings.

Question 12

If the SWC system is not circulating what are the concerns with the water in the system and what actions must be taken?

Answer 12

The generator must be removed from service under the following conditions:
<.5 umho/cm prior to flow loss - 60 min to restore
SWC
.5>x<9.9 umho/cm prior to flow loss - 3 min to
restore SWC
>9.9 umho/cm prior to flow loss - trip turbine
immediately

Question 13

System pressures from low to high.

Answer 13

SWCS<Hydrogen<Seal Oil