Week 2: CVCS

Question 1

What functions does the Chemical and Volume Control System perform?

Answer 1

Maintain RCS inventory
Provide Seal Water Injection to RCPs
Controls RCS chemistry, activity levels, and boric acid concentrations
Provides a means of filling, draining, and pressure testing the RCS
Provides High Head injection flow to RCS upon SIS

Question 2

What is the function of the Letdown system?

Answer 2

To control the pressure, temperature, and flow rate of the reactor coolant as it leaves the RCS and enters the VCT.

Question 3

What is the function and designation of the Letdown isolation valves?

Answer 3

To isolate the letdown system from the RCS in the event of a leak.
LCV-459 and -460

Question 4

Describe the Letdown Isolation Valve interlocks.

Answer 4

To Open:
-All LTDN orifice iso valves closed
-L_PZR greater than 17%
To Close:
-LTDN orifice iso valves closed
Auto Close
-L_PZR less than 17%

Question 5

What is the function of the Letdown Delay Pipe?

Answer 5

To increase coolant transport time, which allows N-16 to decay prior to leaving containment.

Question 6

What is the function of the regenerative heat exchanger?

Answer 6

To reduce the letdown flow to ~290F
To preheat the charging flow to greater than 475F

Question 7

What is the function of the Letdown Orifices?

Answer 7

To reduce letdown system pressure to 350 psig.
To control letdown flow via 3 orifices; one 45 gpm (A) and two 75 gpm (B and C)
C typically in operation during normal ops for a letdown flow of 75 gpm; A opened as needed.

Question 8

What is the function and designation of the Letdown Orifice Isolation valves?

Answer 8

To determine which letdown orifices are placed in service.
HV-8149A, B, C

Question 9

Describe the Letdown Orifice Valve Interlocks.

Answer 9

To Open:
-All LTDN iso valves open
-L_PZR greater than 17%
To Close:
-None (These valves should close first and open last)
Auto Close
-L_PZR less than 17%

Question 10

What is the function of the RHR Letdown Control valve?

Answer 10

To control flow from the RHR to the CVCS.

Question 11

What is the function of the Letdown Heat Exchanger?

Answer 11

To cool letdown flow; an outlet CCW valve (TCV-130) maintains outlet temperatures at 115F.

Question 12

What is the function and designation of the Low Pressure Letdown Control valve?

Answer 12

To maintain the pressure downstream of the Letdown orifices at ~350 psig.
This prevents letdown flow flashing to steam as it moves through the letdown orifices.
PCV-131

Question 13

What is the function and designation of the Letdown Temperature Divert valve?

Answer 13

To divert Letdown flow to the VCT if the flow temperatures exceed 137F. This will protect the demins from overheating.
TCV-129

Question 14

What is the function of the Letdown Demineralizers?

Answer 14

2 mixed bed demins; contain HOH resin and function to remove corrosion products. Normally 1 in service.
1 cation bed demin; utilized for pH control.

Question 15

What is the function of the Letdown Reactor Coolant filter?

Answer 15

To remove any resin fines/particulate matter from the Letdown flow.

Question 16

What are the functions of the Volume Control Tank?

Answer 16

Backpressure for the RCP’s #1 seal that ensures coolant flow to the #2 seals
Net positive suction head for the charging pumps
Oxygen control of the Reactor Coolant System by maintaining hydrogen in the RCS during normal operations
Surge Tank for the CVCS
Degasification of the RCS
Make up point for the RCS

Question 17

What is the function and designation of the VCT Level Control valve?

Answer 17

To direct flow to the VCT or RHT per the VCT level control program.
LCV-112A

Question 18

Describe the VCT level control program.

Answer 18

97% - High level alarm/backup full divert to RHT
88% - Full divert to RHT
60% - Full divert to VCT
50% - Auto-makeup off
30% - Auto-makeup on
5% - Protection

Question 19

Describe the VCT protection response.

Answer 19

At 5% level, the VCT is isolated and the RWST is unisolated for CCP suction.

Question 20

What is the function and designation of the VCT Isolation valves?

Answer 20

To isolate the VCT outlet upon receiving a protection signal.
LCV-112B and -112C

Question 21

Describe the function of the charging system.

Answer 21

To take suction from the charging header and discharge to the Seal Injection system and RCS.

Question 22

What is the function of the Centrifugal Charging Pumps?

Answer 22

To increase fluid pressure in order to force flow into the RCS and Seal Injection system.
2 pumps, 2485 psig output, controlled by FCV-121.

Question 23

What is the function and designation of the Charging Flow valve?

Answer 23

To maintain a backpressure on the common discharge header to control RCP Seal Injection flow.
HCV-182

Question 24

What is the function of the Seal Water System?

Answer 24

To provide Seal Injection and Seal Return flow for the RCPs.
Injection flow, 8gpm/RCP -> 5 gpm/RCP enters RCS -> 3 gpm/pump Return flow

Question 25

What is the function of the Excess Letdown System?

Answer 25

To maintain flow balance between letdown and charging if normal flow path is isolated.
Nominal flow rate is 20 gpm to replace Seal Injection lost to RCS.