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Flashcards in WC- Normal Chilled Water Deck (38):

What is the purpose of the WC system?

To provide chilled water at ~45F to the cooling coils of the Normal Heating, Ventilation and Air Conditioning systems in the Containment, Control, Aux, and Radwaste buildings

Chilled water is also sent to Non-nuclear process sampling coolers, polishing demineralizer sample coolers, blowdown demineralizer sample coolers, and main generator collector housing cooler


What is the interlock associated with the Containment ACUs?

Closes an isolation valve, stopping chilled water flow when the fan is not running


What system provides cooling to each chiller package? What is the tonnage of each chiller package?

Nuclear Cooling Water (low flow of NC will cause the chiller to trip)

A, B, C are 800 tons
E02 is 213 tons


What is the power supply to ‘A’ Normal Chiller?



What system is used as a makeup source of water for WC?



What powers the WC circulation pumps? What is special about the WCN-E01A circulation pump power supply?


SIAS load shed MCC


What system powers ‘B’, ‘C’, and ‘E02’ chillers?



What is the interlock between Circulating water pumps and the respective chiller nuclear cooling water outlet valve? What system can I use if NC is unavailable for cooling?

When the pump starts and stops the valve opens and closes



What are the three WC circ pumps associated with the large chillers rated for?

1200 gpm @ 100ft


What is the E02 circulating pump rated for?

320 gpm @ 100 ft


Why does the WC chiller compressor start after a time delay?

To allow oil pressure, chilled water and cooling water flows to establish


Where are the WC circ pumps located? Were Is the surge tank located?

both on the roof of the Aux Building


What is the normal level of the WC Expansion Tank? What is the capacity?


270 gallons


At what pressure is Nitrogen maintained in the WC Expansion Tank?

15 psig


What are the high and low pressure setpoints for the WC Expansion Tank? What are the low and high level set points?

High – 45 psig
Low – 5 psig



When will the Expansion tank relief lift? Vacuum breaker?

60 psig



When would the makeup valve open and close for the Expansion Tank? What is the make up source?

Opens at 24” and closes at 48”



Where is the WC Chemical Addition Tank located? Capacity?

Roof of the Aux Building, north of chiller ‘A’

11 gallons


What are the precautions associated with adding chemicals to WC?

Water drained form the system must be disposed of properly

Do not add more than one chemical at a time

Operator will wear apron, face shield, and gloves when draining, venting, pumping chemicals, or removing the tank’s cap

Temporary eyewash station will need to be obtained and placed near the Chemical Addition tank for safety purposes


In the WC system, What does PH provide power to?

motor operated containment isolation valves


How does the WC system interface with the NN system?

power for instrument and controls


How does the WC system interface with the CM (chemical waste management) system?

receives all water drained/vented from the WC system to the chemical waste neutralizing tanks


Why would the WC circulating water pump be started without the chiller package operating?

during low heat loads and only one chiller is necessary.

running only one pump provides marginal flow through the system.

(this bypassed flow by the second pump will raise the temperature of the chilled water flow slightly but increases the amount of heat load the single chiller can carry stably)


Normally, the WC chemical addition tank is isolated. What is its status when cold weather protection is in effect?

flow will be aligned to the tank to prevent freeze damage


What is the flow path of the WC chillers?

The low pressure and temperature saturated Freon vapor from the Cooler is drawn into the suction of the Compressor and is compressed; increasing both the temperature and the
pressure of the gas (adding sensible heat).

The high pressure and temperature super-heated Freon vapor enters the top of the condenser where it interacts with the upper tube bundles and starts to transfer sensible heat to the NC (EW back up) system until it becomes a saturated vapor.

As the saturated Freon vapor continues to interact with the NC (EW back up) flowing through the tubes it
will transfer latent heat and start condensing until it becomes a saturated liquid.

The saturated Freon liquid enters the bottom of the Condenser (the Thermal Economizer)
transferring more sensible heat to the NC (EW back up) entering the Condenser, causing it to sub-cool.

The sub-cooled Freon liquid is driven out of the Condenser’s Thermal Economizer and into the Flash Economizer. In the Flash Economizer it enters an enlarged volume tank which causes the pressure to drop and some of the liquid to flash back to a vapor. The Freon liquid that flashes
to vapor further sub-cools the remaining Freon liquid.

The sub-cooled Freon liquid is driven out of the Thermal Economizer and into the Cooler where it interacts with the WC flowing through the tubes and absorbs sensible heat, thereby cooling the WC.

As the Freon liquid continues to interact with the WC it will start to absorb latent heat and flash back to a low pressure and temperature, super-heated Freon vapor.


What is the Chilled water return temperature to the WC chillers?



What increases and decreases the WC chiller capacity as the chilled water temperature raises and lowers?

inlet guide vanes controlled by the chill water outlet temperature


What is surging? What causes it?

when the differential pressure between the condenser and the cooler (lift) is greater than the pumping capacity of the compressor and the refrigerant vapor ends up flowing backwards through the compressor to the cooler until the D/P is below compressor capacity. then the process repeats

decreased condenser cooling water flow, increased temp. in condenser cooling water, fowled condenser tubes, decrease in chilled water temp (low load condition).


What is the maintained condenser cooling water flow through the normal chillers?

>2500 gpm for large units

>500 gpm for small unit


What minimizes or prevents surging? How?

hot gas bypass

basically creates artificial heat load in the cooler


What is stacking? what causes it?

When the differential pressure between the cooler and the condenser is so low, there isn't enough lift to force refrigerant back to the cooler and accumulates in the condenser

low condenser cooing water temp, reduced chilled water flow, high chill water temp


If the WC chillers start and trip right away, how long is the timer set for until they can be started again?

20 minutes from initial start


What is the auto load recycle feature on the WC chillers?

if chill water temp. from the cooler drops to 5*F less than the set point (38*F) the compressor will turn off. there is a 15 minute timer that will allow the chill water circulating pump and lube oil pump to run but prevent the compressor from running until temperature reaches 5*F above the set point


In regards to the WC system, what happens when the containment normal ACUs fans stop running?

the chill water supply valve closes


Describe the containment isolation valves for the WC supply and return through containment.

Two valves on each line, one inside and the other outside containment. the supply line has one motor operated valve outside and a check valve inside. the return line has motor operated valves inside and outside containment

outside valves are in the mechanical penetration rooms on the 94' aux building. inside valves on the 100'.

all close on a CIAS


What is the maximum number of WC chillers that can be ran at one time?

two large and the small

(generally, the two large chillers can handle the high heat load)


What happens when the WC loses IA?

supply valves to the containment normal ACUs and charging pump room normal ACUs fail open

aux building, radwaste/control building isolation valves fail closed

no auto make up to the expansion tank


How is the plant affected when NC is lost?

running normal chillers will trip on low condenser cooling water flow

will align EW to NC priority loads

can only operate one normal chiller