Flashcards in Normal Chilled Water Deck (26)
What does normal chill water supply?
Containment building, control building, aux building, and rad waste building AHUs and ACUs
Non nuclear, demin, blowdown demin sample coolers
Main generator collector housing coolers
What happens to chilled water supply to the containment ACUs when the fan is not running?
An interlock with the fan circuit closes a motor operated valve stopping chill water flow when the fan isn't running.
How are the chillers operated during times of low heat load?
Only one chiller is operated, but a second circulating pump may be started with its discharge valve throttled to boost system flow without running the second chiller.
This is done to raise the chill water temperature slightly allowing the operating chiller to carry more heat load and operate more stable.
How many chillers may be run at max heat load?
2 large chillers and one small chiller.
What are the specific loads of concern on a loss of WC?
Containment normal AHUs (tech spec)
Containment refueling purge
Containment power access purge
CEDM control cabinet room
Generator collector housing cooler
What supplies cooling water to the chiller packages?
NC and the chiller will trip on low NC flow
What is the power supply to the A chiller?
Where does makeup water for WC come from and where is it added to the system at?
DW is added to the expansion tank
What is added to the system for corrosion control?
N2 is added for corrosion control and for NPSH for the pumps.
What is the power supply for the WC circ pumps?
What is the power supply for the B, C, and E02 chillers?
Where are the WC circ pumps located?
On the aux building roof adjacent to their chillers.
What is the N2 pressure maintained on the expansion tank?
What is the driving force for chem adds to the WC system?
D/P across the pump
How is cooling rate in the compressor controlled?
Automatically by varying the inlet guide vanes positions at suction of the compressor in order to vary refrigerant flow through the compressor
How is efficiency improved on the normal chiller units?
An interstage connection between the first and second stages improves efficiency by receiving flash gas from the flash economizer allowing single compression of that portion of refrigerant gas.
The thermal economizer in the condenser portion improves efficiency.
When does the oil pump energize in the startup sequence?
28 seconds before the compressor starts.
How does the flash economizer increase efficiency?
It has 2 sections, each having a float valve. Sub cooled liquid passes through the high side float valve into the economizer then through a low side float valve. Pressure reduction and expansion takes place reducing the fluid temp. Some of the fluid flashes to vapor due to entering a low pressure region removing more heat. The vapor goes back to the 2nd stage compressor.
What is surging?
It occurs during low load operations.
Pressure in the condenser momentarily becomes higher than the pressure at the compressor discharge allowing back flow into the compressor.
It's minimized by the use of a hot gas bypass. The hot gas bypass increases the refrigerant temp. In the cooler causing chill water temp to increase causing inlet vanes to open some and maintain adequate discharge pressure.
What is stacking?
Low load conditions that result in excessive condenser cooling cause it.
Flow rate through the compressor to the condenser is low. The D/p between the condenser and cooler decreases and refrigerant starts stacking up in the condenser while refrigerant level in the cooler decreases.
Stacking is not normally a problem with these chillers.
How long do you have to wait to restart a chiller after a trip?
15 minutes (white light is on during timer)
How long do you have to wait to start a chiller that was manually shut down?
What must chill water temperature be to reset the start circuitry after an auto load recycle?
What will auto close the containment normal chill water isolation valves?
What is the power supply to A chiller circ pump?
NHN- M19 SIAS load shed panel. AO must reset it after Load shed and PB is re energized