NC- Nuclear Cooling Flashcards
Where are the NC pumps located?
The yard area, plant north of the west end of the Turbine building, between the NC heat exchangers and the Condensate Storage Tank
What are the NC pump capacities?
100% at 17,500 gallons per minute
What is the NC pump normal discharge pressure?
100-110 psig
Under normal operations, what is the status of the NC pumps?
One is running, the other is mechanically and electrically aligned in standby
What are the NC pump power supplies?
‘A’ – NBN-S01
‘B’ – NBN-S02
What would cause the standby NC pump to start automatically?
If the combined discharge header pressure at the discharge of the pumps lowers to 79 psig due to trip of the operating pump, pump degradation, improper system operation or system piping breach
How would the operators in the Control Room know if an NC standby pump has auto started and currently running?
An amber light on board 7 will illuminate
Concerning the NC heat exchangers, what flows through the tubes and what flows through the shell side?
PW flows through the tubes and absorbs heat from NC water flowing through the shell side
Where are the NC Heat Exchangers located?
The yard, north of the west end of the turbine building, next to the NC pumps
Before shifting operation to the standby heat exchanger, what must be done with it first?
The on-coming heat exchanger is vented on both shell and tube side to ensure a filled condition
Using the NC heat exchangers, how do we manually adjust temperature? What is the maintained temperature of this system?
By allowing a portion of the flow to bypass the heat exchanger
(So if PW temperatures start to lower, we’ll adjust the bypass valve open more so that less water flows through the cooler. PW temperatures rising would be the opposite)
75-105*F
Concerning the two flows through the NC heat exchanger, which one is at a higher pressure?
NC at the heat exchanger inlet is maintained below PW system pressure to prevent potentially contaminated nuclear cooling water leakage into the PW system and environment
What are the functions of the NC surge tank?
Accommodate changes in system volume due to temperature changes
Provide adequate NPSH for NC pumps
Provide means of detecting leakage into or out of the NC system
Provide a convenient location for adding makeup water
Where is the NC Surge Tank located? What is the capacity?
Roof of the Aux Building, northeast corner
1000 gallons
What provides makeup water to the NC Surge tank and what is the level maintained at?
Demineralized water, maintaining approximately 27-33 inches
What is the backup source of makeup water to the NC surge tank? Where are the valves to align this back up make up source?
Cooling water Holdup Tank (Chemical Waste System)
100’ aux building, south wall
Why do we put nitrogen into the Surge tank? How much is maintained in the tank?
To provide a cover gas that will prevent oxygen intrusion that could lead to corrosion, set at ~5 psig
After chemicals are added to the Chem Add Tank, how we get them into the system? Capacity? Location?
Differential pressure developed by the running NC pump
11 gallons
north yard by NC pumps
The NC Chem Add Tank is normally isolated. Besides adding chemicals, when would we align flow through it and why?
When Cold Weather Protection is in effect to prevent freeze damage
Where is RU-6 located? What is the purpose of this radiation monitor?
The yard north of the Turbine Building, adjacent to the NC pumps
monitor NC system for in-leakage from the contaminated systems it serves
What is the purpose of the Letdown Heat Exchanger Temperature Control valve?
NCN-TV-223 – to automatically regulate the LDHX outlet temperature at the setpoint chosen by the control room operator, normally 120F, by controlling NC flow through the heat exchanger
Where is the Letdown Heat exchanger temperature control valve, NCN-TV-223, located?
110’ Aux Building above the LDHX
Why, as AO’s, should we worry about the flow of NC through the LDHX? What is the maximum NC flow rate through the letdown HXs?
Because it controls Letdown temperature and could ultimately affect reactivity
1500gpm
What are the NC Priority heat loads?
Normal Chillers
Nuclear Sample Coolers
CEDM Normal ACUs
RCP Seal coolers, HP coolers, Thrust Bearing Coolers, Motor Air coolers, Lube Oil Coolers
What is the purpose of the relief valve NCE-PSV-617?
Protect the containment NC return penetration from exceeding its design pressure rating after a LOCA
It protects the system between the inside and outside containment isolation valves
Why are we worried about overpressure in the penetration piping for the NC system between the inside and outside isolation valves?
The water trapped in the penetration piping could be heated by the conditions in the containment and the resulting expansion might rupture the piping and cause a loss of containment isolation
Why do we not have relief protection on the supply penetration piping for the NC system?
Because the inside containment valve is a check valve which would pass flow and therefore not allow any pressure accumulation in the piping
What is the purpose of relief valves protecting NC inside containment?
Protect the NC system piping inside the containment against over pressurization and potential damage in the event of leakage from a RCP seal cooler into the NC system in conjunction with a closure of the NC containment isolation valves
The setpoint for the NC inside containment relief valves is 135 psig. Why is that significant?
Low enough to require a special operating sequence for the NC motor operated containment isolation valves because isolation of the containment return path with the supply path still aligned can cause a pressure surge in the NC system that will lift the reliefs
What types of valves are on the supply and discharge lines through containment for NC? What would cause the NC supply and return containment isolation valves to automatically shut?
supply line- motor operated outside, check valve inside
return line- motor operated valves inside and outside containment
CSAS
What system provides a backup source of cooling water for NC system loads?
EW
If NC is lost to the RCPs, how long would I have to restore it?
10 minutes
3 minutes if its lost to more than one RCP
What temperature is NC maintained at and what is preferred?
Between 75F and 105F, but less than 85F is preferred
The PW T-mod was designed to cool NC when the heat load consists of what components?
One Spent Fuel Pool heat exchanger
Two Normal Chillers at 50% load
BAC at 40% load
LRS Evaporator at 50% load
AS Vent Condenser
What is the purpose of the NC system?
provide cooling during all modes of operation to the priority and non-priority loads
intermediate buffer volume between plant cooling water and potentially contaminated flow streams to reduce the probability of releasing radioactivity to the environment.
Why is the NC constantly monitored by a radiation monitor around the NC pumps?
due to the potential for leakage into the NC system from other radioactive systems
What protections does the NC surge tank have?
hi-lo level/pressure, level sight glass and controller, local temperature indicator, pressure relief and a vacuum breaker
What potential impacts on the plant does manually controlling letdown temperature?
too much NC flow, letdown too cool, boron absorbed, positive reactivity
too little NC flow, letdown too hot, boron released, negative reactivity
What are the NC “non-priority loads”?
letdown hx radwaste evaporator boric acid concentrator waste gas compressors non-nuclear sample coolers aux. steam vent condenser gas stripper aux. steam rad. monitor (ru-7) cooling coil spent fuel pool cooling hx
What must be done prior to opening the EW-NC cross-tie valves?
close the NC non-priority load isolation valve
Where is the NC non-priority load isolation valve located?
77’ aux. building unassigned room
Where are the EW cross-tie to NC valves located?
70’ aux. building, shutdown cooling hx room
Are the isolation valves to transfer EW to NC for the fuel pool hx make-before-break?
yes
In the NC system, what does NH power?
NC pump motor space heaters
CEDM ACU and normal chiller NC outlet valves
In the NC system, what does NK power?
NC surge tank make up solenoid valve
In the NC system, what does PH power?
NC containment isolation valves
What is the back up cooling water system for the shutdown cooling HXs?
NC
What is the back-up make-up system for the NC system?
CM
Which NC HX is the PW T-Mod usually hooked to?
B
What status does cross-tying the EW to NC loads put the EW equipment in?
INOPERABLE
What happens when NC is lost to the WC system?
normal chillers trip
Are the NC supply and return line motor operated valves fail close or as is?
fail as is
What is the tech spec related to the NC system containment isolation valves?
must be able to close in 60 seconds
