CVCS Letdown Flashcards
State the purpose of CVCS Letdown.
Provides a means of PZR level and pressure control.
Provides a means for cleaning up and controlling RCS chemistry.
Provides a means for adjusting boron concentration over core life and as a function of RCS temperature control.
How many gallons per percent level in the PZR.
1 % in the PZR = 66 gallons.
How does a decrease in LD temperature affect RCS temperature?
LD decreases, which causes the IX’s to pull more boron out of LD, which will dilute charging and cause a net positive amount of reactivity to be added to the Rx. This is analagous to withdrawing control rods and thus RCS temperature will increase.
What are the trips associated with CHA-UV-516?
SIAS
CIAS
Train A
What are the trips associated with CHB-UV-515?
SIAS
HI temp: >413F from RHX outlet
Train B
What is the setpoint of the RHX outlet relief valve? and why?
Set to relieve to the EDT at 600 psig to prevent saturation conditions in the RHX?
What is the purpose of the delay coils?
Allows N-16 to decay before letdown enters the Aux Bldg. Located inside containment.
What are the trip setpoints for CHB-UV-523?
CIAS
HI temp > 135F( can be overridden by going back to open-restores LD on high temperature)
Train B
What is the purpose of the LD pressure regulator valves, 110 P/Q?
What are their fail states and how are they operated on startup and shutdown?
Control LD flow from a signal from PLCS to 30 to 130GPM(150 in manual).
They fail closed on loss of power and IA.
Must operate 2 in parallel on low pressure < 1050 psia and isolated on > 1000psia on s/u.
Why is there a possibility of 0.5 gpm bypass flow through HV-526?
How long must bypass flow exist to warm up the LDHX?
Allows warmup of LDHX if isolated for > 22 min.
>4 min.
What is the purpose of the LDHX?
What cools the LDHX, how is temp controlled and what auto feature exists?
Lower LD temperature to protect the IX resin. < 120F.
It is an OPEN LOOP with NC outlet valve in auto. Has a minimum setpoint of 39GPM in auto.
What is the purpose of the TE-224 instrument?
What auto actions does it initiate?
Protects IX, Boronometer, RU 155, IX resin and LDHX.
Provides inputs to:
CHB-523 > 135F closed
CHN-520 > 135F bypass
CHN -521 > 135F bypass
CHN-201 P/Q > 148F Closed
What is the purpose of the LD pressure control valves, 201 P/Q?
What are the associated setpoints and auto features?
How do they fail?
maintain backpressure in the LDHX and associated piping to prevent flashing.
Maintains 375psig. Auto closes 148F.
Fails closed on loss of NNN-D12.
What is the setpoint for the PSV-354 low pressure relief valve?
200 psig, relieves to EDT. Protects d/s piping of the backpressure control valves.
What are the 3 types of IX’s?
Deboration(rx control late in core life)
purification(throughout core life)
Delithiation(periodically to remove lithium)
What does RU-155D tell the operator?
If >= 1 % fuel has failed.
When does CHN-500 divert on VCT level?
when does it realign?
how does it fail?
> 60% will bypass to the PHIX(goes to the HUT)
will realign on < 58% and decreasing.
Fails to VCT on loss of air/ loss of power.
What happens on a DIVERT after the water is bypassed by CHN-500?
CHN-565 aligns to PHIX’s, CHN-566 will divert to EDT on high level in Gas stripper.
Gas stripper is normally bypassed so that the water goes straight to the HUT.
what are the fail states of the following valves:
CHN-565
CHN-566
CHN-567
- Fails to bypass
- Fails to EDT
- Fails to VCT
What is the purpose of CVCS?
Chemistry control of RCS
Removes gases
boron rx control
aux spray
seal injection and bleedoff
ECCS borated water source
What is the design basis of the RWT level?
Provides at least 20min of full flow ECCS pumps prior to reaching RAS signal level < 9.4%
When are both LD control valves placed in service?
When is one removed on startup?
What is the consequence if both valves are left in service at NOP?
on shutdown, when RCS pressure is < 1050psia
on startup when RCS pressure is > 1000psia
Will lift intermediate pressure LD relief valve(@ 600psia)
When are both LD backpressure control valves placed in service?
When is one removed from service on startup?
on shutdown when < 750psia.
on startup when > 1000 psia.
What type of monitor is RU-155D and what is it designed to detect?
RU-155D is an area(process for test) monitor set to measure for >1% failed fuel.
