Charging and Let Down Subsystem

Question 1

What are the basic functions of the CVCS system?

Answer 1

a) maintain boron concentration, purity, chemistry and inventory in the RCS
b) means of removing gases from solution
c) means of processing and recycling liquid radwaste
d) provide RCP seal injection, controlled bleed off, and aux spray
e) provide borated water source for boration, ESF, and SFP
f) provides leak detection, limited make-up capability, and sampling

Question 2

The CVCS system is designed to accept let down and provide required makeup for what heatup and cool down rate?

Answer 2

75F/hr heat up or cool down

Question 3

How does the CVCS system provide for boron concentration adjustments?

Answer 3

feed and bleed

Question 4

How long will the RWT last as a source of borated water after a LOCA and safety injection initiates?

Answer 4

20 minutes plus 10% margin

Question 5

Where is let down initiated at from the RCS?

Answer 5

just upstream of RCP 2B

Question 6

What is the delay coil and what does it do?

Answer 6

it is a larger section of piping (16”) designed to slow flow enough for N-16 to decay. They give a 95 second delay

Question 7

What are the two fluids exchanging heat in the regenerative heat exchanger?

Answer 7

Letdown is giving its heat to charging

Question 8

Where do the letdown flow control valves get a signal from to control their positions?

Answer 8

pressurizer level controller

Question 9

Where does shutdown purification tap into let down?

Answer 9

upstream of the letdown HX so that purification can occur during shutdown

Question 10

What cools the letdown Hx?

Answer 10

nuclear cooling water on the shell side of the hx.

Question 11

What is the purpose of the two backpressure regulating valves downstream of the let down hx?

Answer 11

maintain upstream pressure so that flashing does not occur in the letdown line

Question 12

What is the purpose of the 3 ion exchangers that let down flows through?

Answer 12

two are purification IX and the third is a deborating IX.

Question 13

What do the IX’s remove from the system?

Answer 13

one is always dissolved ionic materials and particulate. A second is used periodically to remove lithium from rx coolant for pH control. The third is used near the end of core life to remove boron in order to minimize liquid waste accumulation.

Question 14

What will cause letdown to bypass the IX?

Answer 14

High temperature

Question 15

How does let down enter the VCT?

Answer 15

through a spray nozzle at the top of the tank gas space. The space is filled with hydrogen during normal ops to scavenge O2.

Question 16

What does the VCT do?

Answer 16

a) acts as a surge tank for RCS to accommodate small mismatches between actual and program Pzr level
b) collect RCP bleed off
c) provide NPSH for charging pumps

Question 17

How many charging pumps are normally in service?

Answer 17

2 (1 always, 1 normally, and 1 in standby)

Question 18

Where does charging tap into RCS?

Answer 18

between 2A rcp discharge and the rx vessel

Question 19

What will automatically close CHB-UV-515?

Answer 19

413F on the outlet of the Regen HX or SIAS

Question 20

What will close CHA-UV-516?

Answer 20

SIAS or CIAS (containment isolation actuation signal)

Question 21

What will close CHB-UV-523?

Answer 21

CIAS or let down HX outlet temp of 135F

Question 22

Why don’t valves 515, 516, and 523 (unit 1 only) have handwheels?

Answer 22

because the handwheels could no longer operate against the increased spring pressure. spring pressure was increased to ensure that the valves will isolate on a LOCA (letdown line)

Question 23

What is the biggest safety concern with the RHX?

Answer 23

it is a large crud trap with high rad levels during outages

Question 24

Why would we want to preheat the charging water with the RHX?

Answer 24

minimize thermal shock on the RCS inlet nozzle

Question 25

How do the letdown control valves fail on a loss of air or power?

Answer 25

closed

Question 26

What flow values do the let down control valves limit flow to and why?

Answer 26

lower limit 30 GPM because the valve can't really control at any lower flow rate. upper limit of 135 GPM to prevent channeling in the IX.

Question 27

When are both let down control valves placed in service?

Answer 27

when RCS pressure is less than 1050 psia to allow adequate let down flow (flow is limited by RCS pressure and D/P)

Question 28

What is the purpose of the letdown control valve bypass valve?

Answer 28

it allows 1/2 GPM of flow around the letdown control valves through an orifice to warm the Let down HX and downstream components if let down has been secured while at power.

Question 29

How long must the bypass be opened for if let down has been secure for >22 minutes?

Answer 29

at lease four minutes prior to initiating let down to minimize thermal stresses

Question 30

What pressure do the let down backpressure control valves maintain upstream and downstream of the valves?

Answer 30

350-375psig upstream | 40-95psig down stream

Question 31

At what temperature do the back pressure control valves isolate the let down HX?

Answer 31

148F

Question 32

When are the purification filters replaced?

Answer 32

D/P >25 psid at 72GPM flow or rad levels > 5R/hr

Question 33

What is the set point of RU-155 and where is it located?

Answer 33

85 mR/hr | it is in the middle of a loop in the let down piping in the aux building on the 120Ft level

Question 34

What type of resin is in the purification IX?

Answer 34

mixed bed H-OH

Question 35

What type of ion exchanger is used for de-borating?

Answer 35

Anion

Question 36

What are the flow and temperature limits for the purification IXs?

Answer 36

150 GPM to prevent channeling and 140F to prevent resin bed damage

Question 37

What happens in the IX when let down/NCW temperature increases?

Answer 37

boron will come out of the ions and drop RCS temperature

Question 38

What is the capacity of the VCT?

Answer 38

4900 gallons

Question 39

What is the normal level in the VCT?

Answer 39

33-44%

Question 40

When will CHV-501 close?

Answer 40

when level in the VCT is at 5% (prevents air binding of the CH pumps)

Question 41

What will cause CHV-536 to open automatically?

Answer 41

if CHV-514 loses power and VCT is <5%

Question 42

What pressure is the VCT normally maintained at?

Answer 42

between 20 & 25psig

Question 43

What do the charging pumps provide?

Answer 43

a) RCS makeup b) aux spray c) RCS boration d) RCP seal injection

Question 44

Where do the charging pumps get power from?

Answer 44

PGA or PGB

Question 45

What are the 3 modes of operation for the charging pumps?

Answer 45

a) always running (no automatic signals or controls will stop the pump) b) normal running mode (high pzr level will stop the pump, but when the alarm clears, the pump will re-start) c) standby mode (low level in pzr will start the pump and the pump will stop when the condition clears)

Question 46

When does the charging pump seal water pump start?

Answer 46

when its associated CH pump starts if the seal water pump is in auto.

Question 47

How long can you run a charging pump without seal water in an emergency?

Answer 47

50 hrs

Question 48

What are the bladders on the suction stabilizer and pulsation dampeners filled with?

Answer 48

N2

Question 49

What is the purpose of the charging line backpressure control valve (CHN-PDV-240)?

Answer 49

a) maintain back pressure for Aux spray b) back pressure for RCP seal injection c) back pressure to minimize charging pump pulsations d) fails closed on loss of power or instrument air

Question 50

What is the purpose of CH-V239?

Answer 50

if CH-V240 fails open, it would close to ensure Aux spray is available

Question 51

Why is there a spring loaded check valve installed to bypass CH-V239 & CH-v240?

Answer 51

maintain 200 psid back pressure and allow for isolation of the two valves for maintenance or failure

Question 52

What are the power supplies to the Aux spray valves?

Answer 52

PKA & PKB

Question 53

What is used to heat the seal injection heat exchanger?

Answer 53

Nothing, the aux steam is currently blanked off.

Question 54

How many filters are normally in service in the seal injection line?

Answer 54

One

Question 55

What will cause the RCP seal injection bleed off valves to auto close?

Answer 55

CSAS, but flow will still be available via a relief valve to the RDT.

Question 56

What components make up the chemical addition unit?

Answer 56

Chem add tank, outlet strainer, and chem add pump

Question 57

Where does the chem add pump discharge to and why?

Answer 57

Charging header just upstream of the RHX. Allows addition of chemicals to RCS when charging header containment isolation valve is closed and prevents the addition of a high pH fluid directly into CH pump suction

Question 58

What is the capacity of the chem add tank?

Answer 58

8 gallons

Question 59

What supplies water to the chem add tank?

Answer 59

RMW

Question 60

What is the capacity and power supply to the chem add pump?

Answer 60

Max of 25 GPH and it's powered from NH.

Question 61

What chemicals are added to the RCS while the plant is shut down?

Answer 61

Hydrazine and hydrogen peroxide

Question 62

What does hydrazine do?

Answer 62

Scavenges O2 at <250F

Question 63

What is Lithium added to the primary for?

Answer 63

Increase pH near end of life. | Lithium 7 is also used to reduce tritium production.

Question 64

Where can the RMWPs discharge to?

Answer 64

RX makeup supply header, RWT, batch tank eductor, or directly to CH pump suction.

Question 65

What type of water is stored in the RWT?

Answer 65

Borated water

Question 66

Where do the BAMPs take a suction from?

Answer 66

Refueling water tank

Question 67

What is the capacity of the RMWT?

Answer 67

480,000 gallons.

Question 68

What tank is an alternate source of water for the A & B AFPs?

Answer 68

RMWT

Question 69

Where is the RMWT vented to and where does it overflow to?

Answer 69

Vented to atmosphere | Over flows to hold up tank sump

Question 70

What type of valve is CH- 210X?

Answer 70

CCI drag disk stack valve

Question 71

What does ch-210x do?

Answer 71

Controls flow of RX m/u water flow to the VCT through make up stop valve 512.

Question 72

Where does the operate signal come from for 210X?

Answer 72

From the makeup controller and is controlled from B03. With the VCT makeup controller in dilute mode, the flow control valve closes when the flow reaches the desired total.

Question 73

What is the capacity of the RWT?

Answer 73

750,000 gallons

Question 74

What is the required boron concentration for the RWT?

Answer 74

4000-4400 ppm

Question 75

Where can the RWT send water to?

Answer 75

BAMPs, CH pump suctions, spent fuel pool, spent fuel pool clean up pumps, ESF pumps

Question 76

Where is the RWT vented to?

Answer 76

Fuel building normal exhaust

Question 77

Where can the BAMPs take a suction from?

Answer 77

RWT or spent fuel pool

Question 78

What limits the output capacity of the BAMPs?

Answer 78

BAMPs can put out 165 gpm, but CH-V210Y can only pass 150 gpm, so the BAMPs may not be able to exceed the capacity of 3 charging pumps running like they should.

Question 79

What valve is the boric acid flow control valve and what type of valve is it?

Answer 79

CH-210Y. And it is a drag disk stop valve