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Flashcards in PW- Plant Cooling Water Deck (34):

What are the functions of the PW system?

Remove heat from the TC, NC, and AR systems and reject that heat to CW

Fill condenser water boxes and CW system during startup or after condenser maintenance

Provide water to the CW screen wash area hose connections

Provide water to the chlorine injection system acid injection static mixers


What is the capacity of the PW pumps? Where do they receive power from? What powers the motor space heaters?

100% each (29,000 gpm)




How are the PW pumps lubricated and cooled? How are the pump and motor shafts connected?

Oil lubricate and air cooled

flexible flange coupling


What is the automatic feature associated with the PW pumps?

Standby pump will automatically start when a low pressure condition (~40 psig) is sensed on the discharge of the operating pump

alarm in the control room


How would the Control Room know that the standby PW pump has auto started?

Amber light lit for the associated pump


What are the PW pump power supplies?

‘A’ – NBN-S01
‘B’ – NBN-S02


How would I know that the PW pump trash screens require a wash down?

High differential level (12 inches) observed between the intake canal and the pump suction bay


What impact does a loss of PW have on the plant?

High temperature condition within NC, TC, and AR. If not corrected, a manual trip is required

The Main Turbine immediately feels the loss due to the loss of TC, so numerous alarms would annunciate in the Control Room within seconds of the loss


When is the PW T-mod used?

During outages to provide temporary cooling to Nuclear Cooling Water Heat Exchanger “B” when the Plant Cooling Water system is not available


The PW Temporary cooling system was designed to cool NC when the heat load consisted of what?

One Spent fuel Pool heat exchanger

Two normal chillers at 50% load

BAC at 40% load

LRS evaporator at 50% load

Aux. Steam Vent Condenser


Can I add any more loads to the PW T-Mod then what it was intended for?

Only with the discretion of the Control Room and/or Work Control


What is the general flow path of the PW T-mod?

Two temporary circulating pumps take suction from a portable retention tank and pump the water through NC heat exchanger “B”. The water flow is throttled by flow orifices and the cooling tower inlet valves to ~2400 gpm per cooling tower. The water enters the two portable cooling towers for heat removal via evaporative cooling and flows into the portable retention tank to complete the circuit


What is the capacity of the PW T-Mod Portable Retention Tank?

Normal operating level is ~4000 gallons, but when the system is filled prior to startup or is shutdown and the system allowed to drain back there will be about 5200 gallons in the tank


What is the capacity of the two PW T-mod Circulating Pumps? What powers them?

3000 gpm each



What is the PW T-Mod system’s primary makeup source?

Essential Spray Pond “A” via temporary makeup pumps


What is the PW T-Mod system’s secondary makeup source?

DS return from IA and Service Air compressor when they are being operated on temporary cooling water from DS


What are the power supplies for the PW T-mod equipment?

Unit 1
-Construction Substation N through portable Mobile Substation R to Temporary Panel A, then to equipment
-Construction panel A4 or a portable generator through a portable Manual bus Transfer Switch to Temporary Panel A, then to equipment

Unit 2
-Construction Substation 100 through Portable Mobile Substation R to temporary panel A then to the equipment

Unit 3
-Construction Substation 200 through portable Mobile Substation R to Temporary Panel A, then to the equipment


Concerning the PW T-Mod, what is the blowdown flow rate back to the spray pond?

50 – 120 gpm


Using the PW T-Mod, how could I warm up NC?

Bypass around the HX

If more warming is required and the bypass is full open, outlet valve may be throttled closed


What happens when the normal return flow path for the PW system to the canal is not available?

the alternate return flow path to the #2 cooling tower is used


What side of the nuclear cooling water heat exchanger is the PW system on? Why is this not a concern?

tube side

Due to system layout, only inside the heat exchanger, the PW system is at a higher pressure than NC. Therefore, PW would still leak to the NC in the case of a tube break.


How can the PW pump suction bays be isolated and drained for maintenance?

Sliding stop-gates for insertion just behind the screens


What is the normal discharge header pressure of the PW pumps?



The normal position of the PW outlet valves on the standby HXs is closed. What is the normal throttled position of the PW outlet isolation valves for both the TC and NC HXs that are in service?

33% (30*)


Is swapping NC and TC HXs a make-before-break process?



What is the procedure that operators will use to perform the filling of condenser with the PW system?



What is an AO job while the PW system is filling the condenser?

manually operating the CW auto vent valves


Where are the Circulating water fill valves located?

in pits in the north yard of each unit


How does the loss of PW affect the CI (Chlorine Injection System)?

it would require acid to be added to the canal by an alternate method

(normally, gravity flow from acid storage tanks to an eductor with PW water flowing through it)


How does losing the PW system affect reactor power?

NC system would no longer have a heatsink. NC temp. rises, Letdown temp. rises and affects the Purification ion exchangers.

higher temp = releases boron into charging water and RCS, reduces reactor power


What is the purpose of the flow orifice plates in each NCHX outlet pipe to the PW T-Mod cooling towers?

maintain a minimum back pressure on the HX to ensure it stays full of water during operation


How many fans are on each PW T-Mod cooling tower? Where are they powered from?




What is the normal operating line up of the PW T-Mod?

both cooling towers, both circulating pumps, both make up pumps and all 16 fans operating


Concerning the PW T-Mod, the cooling tower inlet valves are throttled to equalize flow to the towers and maintain outlet pressure from the NCHXs. What is the NCHX outlet pressure normally?

40-45 psi

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