SG- Main Steam Flashcards
Besides the HP turbine, where else does the SG system send steam to?
MSRs
Feedwater Pump turbines
steam seal system for the main turbine and feedwater pump turbines
Aux Feed Pump A
AS system
When is the Main Steam system required to be available? When is the SBCS available?
Modes 1-4, and in Mode 5 under certain conditions
modes 1-4
How are the Steam Generator Downcomer feedwater Control Valves operated and how are they normally controlled?
Pneumatically operated and are normally controlled by the Digital Feedwater Control system
they can also be controlled by operator action in the Control Room
How are the Downcomer feedwater Control valves affected by a loss of air or power?
Fails locked (as-is) on a loss of electrical power or air pressure
At one point, during reactor power operations, will the Downcomer provide 100% feed flow to the steam generators?
At low power operation, below 15%
Concerning the main steam system, what is “Swapover”?
At ~15% power and increasing, Downcomer Control Valves throttle closed and the Economizer control valves throttle open, directing all flow through the economizer lines
Reactor power is ascending. In the SG system, after the downcomer control valves close and the economizer valves open, will it stay in this line-up?
No, at 50% power, the downcomer control valves start to re-open to supply 10% of all feed flow from 50% to 100%
This provides subcooling for the recirculating water and promotes an increased recirculation ratio in the S/G
Where are the steam generator Downcomer Control Valves, as well as the block and bypass valves, located?
120’ Mezzanine area
During Mode 3, what valve is used to feed the S/Gs and what provides the driving force?
S/G Downcomer Control Bypass valves, from the non-essential AFP
How do the steam generator Downcomer Control Bypass valves fail upon a loss of air or power?
As-is
Why are there two steam generator Feedwater Downcomer Isolation Valves? How are they operated?
Upstream valve is “A” train and the downstream valves are “B” train, that way if one fails the other should operate to isolate that line
IA and nitrogen to open, spring close
(can also open manually)
How are the steam generator Downcomer Isolation valves affected by a loss of IA and Nitrogen backup?
The valves fail closed
When would the steam generator Downcomer Isolation Valves fail open? When would they close automatically?
Upon a loss of DC power
steam line break, feedwater line break, LOCA
How can I open the steam generator Downcomer Isolation Valves after being shut by a MSIS?
By placing the switch in the CLOSE position and observing the white OVERRIDE light illuminated
The valve can be opened with the signal still present by taking the switch to the OPEN position
If I lost IA, how long could the steam generator Downcomer Isolation Valves operate with the Nitrogen accumulator backup supply? Where is the nitrogen accumulator and all N2 valves located? What pressure is nitrogen regulated down to?
12 hours
140’ turbine building
240 psig
Where are the steam generator downcomer isolation valves located?
100’ level of MSSS
Where is the water injected into the S/G by the Economizer line? Why?
Cold leg half of the Steam Generator to preheat the incoming feedwater to saturation temperature
Why is the steam generator Economizer line not used during low power operation?
Due to insufficient preheating of the feedwater
How are the S/G Economizer control valves normally controlled?
By the Digital Feedwater Control system
What happens to the S/G Economizer Control valves on a loss of power or air?
Fails locked (as-is)
Where are the S/G Economizer control valves located?
120’ Mezzanine
What is the purpose of the S/G Economizer Feedwater Isolation Valves?
To allow remote isolation of the economizer feedwater line on the outside of the containment in the case of a steam or feed line break or LOCA
What is the difference between the two S/G Economizer Feedwater Isolation valves in each line?
Upstream is “A” train, downstream is “B” train
Where are the S/G Economizer Feedwater Isolation valves located?
120’ MSSS building
What happens to the S/G Economizer Feedwater Isolation valves upon a loss of power? Where does power come from?
Fail closed
supplied from the PK ‘A’ or ‘B’ bus
What happens to the S/G Economizer Feedwater Isolation Valves upon a loss of air?
The valves are designed to not change position and remain capable of fast closing
What signal would shut the S/G Economizer Feedwater Isolation Valves?
MSIS
Concerning the S/G Economizer Feedwater Isolation Valves, when would the Accumulator Charge Test position be selected?
To verify proper Nitrogen pre-charge in the accumulator
Hydraulic pressure must be removed to perform this test
Concerning the S/G Economizer Feedwater isolation valves, what happens when the FAST CLOSE pushbutton is depressed?
5000-5400# accumulators are lined up directly to the top of the cylinder to close the valves
How many U-Tubes are in the S/G and how many can be plugged without affecting steam pressure on the secondary side?
12,580 tubes
10% of the tubes
What provides the changes in S/G diameter from the intermediate shell to the steam drum?
Transition cone