REACTOR COOLANT SYSTEM

Section 3.2

Objectives1. State the purpose of the Reactor Coolant

System (RCS).

2. List and state the purpose of the following RCS penetrations:

a. Hot Leg (Th)

2

h

1. Pressurizer surge line

2. Residual Heat Removal (RHR) suction

3. Sample line

4. RHR recirculation/Safety Injection (SI)

b. Intermediate Leg1. Elbow flow taps

2. Chemical and Volume Control System (CVCS) letdown

3. Loop drain

3

c. Cold Leg (Tc)1. Pressurizer spray line

2. CVCS charging

3. Common injection penetration for RHR, SI, and an Accumulator

4. High head injection

5 E cess letdo n

4

5. Excess letdown

3. Describe the primary and secondary flow paths through the steam generator.

5

4. State the purposes of the following components of the reactor coolant pump.

a. Thermal barrier heat exchanger

b. Seal package

c. Flywheel

d. Anti-reverse rotation device

N b 1 l b l

6

e. Number 1 seal bypass valve

f. Number 1 seal leak off valve

g. Seal stand-pipe

5. Explain why seal injection flow is supplied to the reactor coolant pumps.

7

6. State the purposes of the following:a. Pressurizer (PZR)

b. Code safety valves

c. Power-operated relief valves (PORVs)

d. PORV block valves

e. Pressurizer relief tank (PRT)

f PZR l

8

f. PZR spray valves

g. PZR heaters

7. Describe the methods for determining pressurizer relief and safety valve position and/or leakage.

8. Explain the following:a. Pressurizer spray driving force

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b. Purpose of pressurizer spray bypass

9. Explain how failure of the following components could lead to core damage.

a. Reactor coolant pump seals

b. Power-operated relief valves

10

Purposes of the Reactor Coolant System (RCS) (Obj.1)

• Transfer heat from reactor to power conversion system.

• Provides a barrier to limit the escape of radioactivity to the containment

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radioactivity to the containment.

TE

CVCS EXCESS LD(LOOP 3)

RCP

TETETE

TE

HIGH HEAD SI(FROM BIT)

RHR PUMPS

SI PUMPS

COLD LEGACCUMULATORS

PRESSURIZER SPRAY(LOOPS 2&3)

STEAMGENERATOR

FIGURE 3.2-1 Reactor Coolant Loop Penetrations

12

PRESSURIZERSURGE

LINE (LOOP 2)

FT

CVCS LETDOWNNORMAL (LOOP 3)

CROSS OVERLEG DRAINS

(CAPPED)

FS

TE

RHR SUCTION(LOOP 4)

RHR(LOOPS 2 & 4)

HOT LEGSAFETY INJECTION

SAMPLE(LOOPS 1&3)

Tc

ThREACTOR

CVCS CHARGING(LOOP 1 NORMAL,LOOP 4 ALTERNATE)

(FROM BIT)GENERATOR

BRANCHNOZZLE

HEADER(PIPEWALL)

Figure 3.2-3 Pressurizer Spray Scoop

13

4"

SECTION AA

27-1/2" I.D. FLOW

A

A

Figure 3.2-4 Sample Connection Scoop

PIPE WALL

14

6 1

3.250"

FLOW

REACTOR COOLANTPIPE

1.33" DIA

FLOW

Figure 3.2-5 Hot Leg RTD Tap

FLOW

15

Figure 3.2-6 Reactor Coolant Flow Taps

B

LOW PRESSURETAPS

HIGH PRESSURETAP

15o

16

22-1/2

B

SECTION BB

15o

15o

Fig. 3.2-6 Rx Coolant Flow Taps

Pressurizer Fig 3.2-7

INSTRUMENTATIONNOZZLE

RELIEFNOZZLE

LIFTINGTRUNNION(LOAN BASIS)

UPPER HEAD

PersonWAY

SAFETY NOZZLE

SPRAY NOZZLE

17

Figure 3.2-7Pressurizer

ELECTRICAL HEATER

HEATER SUPPORTPLATE

SURGE NOZZLE

SUPPORT SKIRT

INSTRUMENTATIONNOZZLE

LOWER HEAD

SHELL

• Purposes of PZR (Obj 6.a)– pressurize RCS during plant start-up

– maintain normal RCS pressure during steady state operation (2235 psig)

– limit pressure changes during RCS transients to w/in allowable values.

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– prevent RCS pressure from exceeding design value (2485 psig)

• Purpose of spray valves (loops 2 & 3 cold legs) (4 “ lines) (Obj 6.f)– to limit RCS pressure changes during

transients.

19

• PZR spray driving force - (Obj 8.a)

–The differential pressure across the Rx provides the driving force to spray the PZR.

–The PZR spray scoops are used so the velocity of the RCS flow is added to the

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velocity of the RCS flow is added to the differential pressure across the Rx.

• Purpose of PZR Spray Bypass - manual throttle valves. (3/4") (Obj 8.b)

– provides small continuous flow around spray valves. (Tc ~ 556 deg)

– Reduces thermal stress/shock on spray nozzle. (2235# ~ 653 deg.)

21

– Helps promote mixing in PZR to avoid thermal stratification

– Aids in maintaining uniform chemistry in RCS & PZR.

• Purposes of PZR Heaters (Obj 6.g)– to limit RCS pressure changes during

transients,

– to maintain PZR at saturated conditions. PZR heater elements (78 elements) (1794 KW total) (raise temperature ~ 55 deg/hr)

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– To draw a bubble in the PZR during startup.

• PZR Code Safety Valves (6”)Purpose: (Obj 6-b)– to prevent RCS from exceeding design

pressure by more than 10%.

– Setpoint: 2485 psig.

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• PZR PORVs Purposes: (Obj 6.c)

– Minimize probability of a high pressure reactor trip (2385#) following a 50% load rejection.

– Limit the operation of the code safety valves.

– Mitigate overpressure transients during cold

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Mitigate overpressure transients during cold shutdown.

– Remove decay heat if S/G not available.

• PORV Block Valves. (Obj 6.d)

–Purpose – to isolate PORV if excessive leakage.

25

Pressurizer Relief Tank (PRT) (Obj 6.e)

– Purpose - Collects, condenses, and cools discharge from PORVs and code safety valves.

26

• Describe methods of determining PZR PORV & Position Indication & Leak Detection (Obj 7)

– PORV -stem mounted valve position switch gives actual valve position

– temperature detector on common discharge

27

p g

– Control room indication and alarm

Describe methods of determining PZR Code Safety Position Indication & Leak Detection (Obj 7) (cont)

– Code Safety - indirect valve position indication

– Acoustic monitor on tailpipe of each valve

28

p p

– Temperature detector on tailpipe of each valve

– Control room indication and alarm

Steam Generators• Functions:

– transfers energy from primary to the secondary

– produces dry, saturated steam for use in the main steam system

29

– provides a boundary between primary and secondary (U-tubes)

Model 51SteamGeneratorFig. 3.2-9

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STEAM OUTLET

SECONDARY SEPARATORS(MIST EXTRACTORS)

RECIRCULATING WATER

SWIRL VANE MOISTURESEPARATOR

NORMAL WATER LEVELAT 100% POWER

FEEDWATER INLETNOZZLE

FIGURE 3.2-10 Steam Generator Flow Paths

31

STEAM GENERATORSHELL

TUBE BUNDLE WRAPPER(TUBE SHROUD)

DOWNCOMER

REACTORCOOLANTOUTLET

REACTORCOOLANT

INLET

STEAM - WATERMIXTURE

Figure 3.2-11 Feed Ring Assemblies

Tee connection

FeedringThermal sleeve

S/G Shell

Feedwater line

L

FEEDRING ASSEMBLYFEEDRING TYPE STEAM GENERATOR

32

251-3/4 inch diameter flow holes

J-tubepositions

J-tubes

J-TUBE CONFIGURATIONFEEDRING STEAM GENERATOR

Feedring

SwirlVane

Figure 3.2-12 Feedring and Moisture Seperators

33

Shell

AntiVibrationBar

ORIFICE

SWIRL VANE

TO DRAIN

STEAM

Figure 3.2-13a Steam Generator Moisture Seperators

34STEAM WATER

RISER

TO DRAIN

STEAM &WATERSTEAM

Figure 3.2-13b Steam Generator Moisture Separators

35

TOPEDGE

DRILLED TUBESUPPORT PLATE

TUBESUPPORTPLATE

TUBETUBE

Figure 3.2-14 Tube Support Plate

QUATREFOIL TUBESUPPORT PLATE

TUBESUPPORTPLATE

FLOWHOLE

36

• Describe the Primary and Secondary flow paths in the Steam Generator (Obj 3)– Primary - enter hot leg, divider plate directs

flow through tube sheet and up U-tubes, exit cold leg.

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SECONDARY (STEAM SIDE) FLOW PATH. (Obj-3)

• Feedwater enters through feed ring nozzle (~430 deg. F).

• In downcomer feedwater mixes with recirc water.• Mixture flow under tube bundle wrapper into tube

bundle, producing a steam - water mixture.• Flows up swirl-vane moisture separator.

Moisture removed and drains back to

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Moisture removed and drains back to downcomer.

• Flows through chevron separator. Moisture removed and drains back to downcomer.

• At S/G outlet to main steam system (main turbine generator) (<0.25% moisture content)

STEAMFLOW

STEAMPRESSURE

STEAM FLOW = FEED FLOW

Figure 3.2-15 Steam Generator Shrink and Swell

39

01 100 200 100 20002TIME (SEC)

STEAMGENERATOR

LEVEL

SG Flow Path

Figure 3.2-16 Reactor Coolant Pump

THRUST BEARINGOIL LIFT PUMP+ MOTOR

MOTOR UNIT ASSEMBLY

FLYWHEEL

UPPER RADIALBEARING

THRUST BEARING

MOTOR SHAFT

MOTOR STATOR

MAIN LEADCONDUIT BOX

LOWER RADIAL

40

SEAL HOUSING

NO. 1 SEAL LEAK OFF

MAIN FLANGE

COOLING WATEROUTLET

RADIAL BEARINGASSEMBLY

THERMAL BARRIER ANDHEAT EXCHANGER

CASING

IMPELLER

BEARING

NO. 3 SEALLEAK OFFNO. 2 SEALLEAK OFF

PUMP SHAFT

COOLANT WATER INLET

DISCHARGENOZZLE

SUCTIONNOZZLE

Figure 3.2-16 Reactor Coolant Pump

THRUST BEARINGOIL LIFT PUMP+ MOTOR

MOTOR UNIT ASSEMBLY

FLYWHEEL

UPPER RADIALBEARING

THRUST BEARING

MOTOR SHAFT

MOTOR STATOR

MAIN LEADCONDUIT BOX

LOWER RADIAL

41

SEAL HOUSING

NO. 1 SEAL LEAK OFF

MAIN FLANGE

COOLING WATEROUTLET

RADIAL BEARINGASSEMBLY

THERMAL BARRIER ANDHEAT EXCHANGER

CASING

IMPELLER

BEARING

NO. 3 SEALLEAK OFFNO. 2 SEALLEAK OFF

PUMP SHAFT

COOLANT WATER INLET

DISCHARGENOZZLE

SUCTIONNOZZLE

RCP Seal PackageFig. 3.2-19

42

• Seal Package (Obj 4.b)– Purpose - to provide essentially zero leakage

from RCS (up the pump shaft into containment) during normal operation.

• Purpose of RCP Seal Injection (Obj 5)– RCP Seal Injection supplies cool, purified,

filtered water from CVCS to pump radial

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p pbearing and seal package to prevent seal damage. (3 gal up / 5 gal down)

Figure 3.2-20 Controlled Leakage Shaft Seal

CLOSINGFORCES

SEAL RING(NON-ROTATING)

OPENINGFORCES NET CLOSING

FORCES

EQUILIBRIUM

SEAL PACKAGEHOUSING

.0045"GAP

FLOW

RUNNER(ROTATING)

"O" RINGSEAL

LOW PRESSUREFLUID (50 PSIA)

SHAFT

Seal RingNon-Rotating

44

NET OPENINGFORCES

EQUILIBRIUMFORCES

(ROTATING)

"O" RING SEALHIGH PRESSUREFLUID (2250 PSIA)

• Purpose RCP Seal Standpipe (Obj 4.g)– to maintain sufficient back pressure on

number 2 seal to ensure flow thru number 3 seal.

45

No. 1 Seal Bypass Valve:

(Obj 4.e)

Purpose: It is opened to ensure adequate cooling to RCP lower radial bearing

LO ALARM

200 psid

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radial bearing during low RCS pressure operations.

• RCP Thermal Barrier & Thermal Barrier Heat Exchanger (HX) (Obj 4.a)– Purpose - to cool any reactor coolant leaking

up the shaft to protect the radial bearing and shaft seal package.

– Thermal Barrier HX cooled by CCW.

47

Number 1 Seal Leakoff Valve. (Obj 4.f)– Purpose - the number 1 seal leakoff valve is

closed to place the number 2 seal in service.

48

Figure 3.2-16 Reactor Coolant Pump

THRUST BEARINGOIL LIFT PUMP+ MOTOR

MOTOR UNIT ASSEMBLY

FLYWHEEL

UPPER RADIALBEARING

THRUST BEARING

MOTOR SHAFT

MOTOR STATOR

MAIN LEADCONDUIT BOX

LOWER RADIAL

49

SEAL HOUSING

NO. 1 SEAL LEAK OFF

MAIN FLANGE

COOLING WATEROUTLET

RADIAL BEARINGASSEMBLY

THERMAL BARRIER ANDHEAT EXCHANGER

CASING

IMPELLER

LOWER RADIALBEARING

NO. 3 SEALLEAK OFFNO. 2 SEALLEAK OFF

PUMP SHAFT

COOLANT WATER INLET

DISCHARGENOZZLE

SUCTIONNOZZLE

• Flywheel (Obj 4.c)– Purpose - Extends forced cooling (coast down)

for ~ 30 seconds following a loss of offsite power. This helps to maintain heat transfer and establish natural circulation. Uses stored energy in flywheel.

50

• Anti-reverse rotation device. (Obj 4.d)– Purpose - prevents pump from turning

backwards due to reverse flow in loop. This prevents excessive starting current (overheat motor windings).

51

FLYWHEEL

PAWL

PAWL STOP

Figure 3.2-21 RCP Flywheel and Anti-reverse Rotation Device

52

FLYWHEEL RUNNING POSITION

STOP POSITION

RATCHET PLATE

FLYWHEEL

RATCHET PLATE

PAWL

RCS Leakage Detection• Containment Rad Monitoring System

• Increase in Makeup requirements to maintain PZR level

• Rx Vessel Flange O-Ring high temp alarm

• Containment pressure humidity

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• Containment pressure, humidity, temperature, sump pumping frequencies,

• Primary to Secondary leakage: sampling, Condenser off-gas, SGBD, MSL radiation

• How could failure of RCP Seals lead to core damage? (Obj 9.a)– RCP seal package failure results in a SBLOCA.

– If there is no high head injection pumps to provide make-up water to the RCS, the core will become partially or fully uncovered. (No operator action to reduce RCS pressure is assumed.)

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reduce RCS pressure is assumed.)

– Decay heat will cause fuel temperature to increase. Could lead to fuel damage. Time to core damage is dependent on assumed size of leak.

• How could PORV Failures Lead to core damage? (Obj 9.b)– Failure to close results in a LOCA.

– If PORV block valve does not shut AND if containment sump recirculation mode of ECCS is unavailable, then core will become partially or fully uncovered.

55

– Decay heat will cause fuel temperature to increase. Could lead to fuel damage.

• How could PORV Failures Lead to core damage? (Obj 9.b) (cont)

– Failure to open (when needed) during emergency operations (i.e., once through core cooling)

– Unable to remove decay heat w/ once through core cooling.

– Decay heat will cause fuel temperature to

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Decay heat will cause fuel temperature to increase. Could lead to fuel damage.

Purpose is to detect any loose or drifting metallic parts within the RCS

Figure 3.2-22 Vibration and Loose Part Monitoring Transducer Locations

6

B10

11 C

2

1

43

5

A9

D

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RCS pressure boundary

LOWER VESSEL (WEST)LOWER VESSEL (EAST)UPPER VESSEL (NORTH)UPPER VESSEL (SOUTH)RC PUMP ARC PUMP B

123456

LOCATIONCHANNEL

RC PUMP CRC PUMP DSTEAM GENERATOR ASTEAM GENERATOR BSTEAM GENERATOR CSTEAM GENERATOR D

789

101112

LOCATIONCHANNEL

11

7

12

8

RCS Heatup Limits: TS

• Max. H/U limited to 100 deg. F in any one hour.

Figure 3.2-26 Reactor Coolant System Pressure - Temperature Limits (Heatup)

UNACCEPTABLEOPERATING AREA

HEATUP RATESUP TO 60 F/HR

ACCEPTABLEOPERATING AREA

2000

3000

58

o e ouUP TO 60 F/HR

OAVERAGE REACTOR COOLANT SYSTEM TEMPERATURE ( F)0.0

0.0

100.0 200.0 300.0 400.0 500.0

1000

RCS Cooldown Limits: TS

• Max C/D limited to 100 deg F

Figure 3.2-27 Reactor Coolant System Pressure - Temperature Limits (Cooldown)

3000

2000

ola

nt

Sys

tem

Pre

ssu

re(p

sig

)

ACCEPTABLEOPERATING AREA

UNACCEPTABLEOPERATING AREA

59

100 deg. F in any one hour. 0

204060100

Cooldown Rates°F/hr

0

1000

0 100 200 300 400 500

Average Reactor Coolant System Temperature (°F)

Re

ac

tor

Co

o