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NLO Systems 2023 > RC- Reactor Coolant System > Flashcards

RC- Reactor Coolant System Flashcards

1
Q

What are the three main purposes of the RCS?

A

transfer thermal energy to the S/G

secondary barrier to the release of fission products

provide core cooling during all normal plant conditions

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2
Q

How does the RCS interface with the CEDMCS system?

A

CEDMCS controls the direction, rate, and duration of CEA’s

also controls the magnetic jack coils to CEDM’s

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3
Q

Can CEA motion be controlled automatically or manually?

A

both

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4
Q

How does the RCS interface with the RI (Fixed in-core instrumentation system, or FICS)?

A

measures neutron flux,

coolant temp. in 61 locations

monitors core characteristics to assure we do not exceed allowable limits

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5
Q

In the RCS, what does the RI system control?

A

nothing. it only collects data

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6
Q

How does the RCS interface with the CH system?

A

maintains pressurizer level,

chemistry control,

boron concentration

provides RCP seal injection

collects RCS discharges

supplies aux spray to pressurizer when normal spray path unavailable

purifies RCS

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7
Q

What discharges from the RCS does the CH system collect?

A

drainage for maintenance

RCP seal bleed off

Primary safety valve discharge

identified leakage

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8
Q

How does the RCS interface with the NC system?

A

intermediate barrier between RCS and the PW system

provides cooling to the RCP motor air cooler, lube oil cooler, thrust bearing lube oil cooler, and seal coolers

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9
Q

How does the RCS interface with the SI system?

A

emergency core cooling and boron injection for reactor shutdown

long and short term cooling

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10
Q

When does SDC provide cooling for the reactor?

A

When the S/G’s are unavailable

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11
Q

When does shutdown cooling provide long term cooling?

A

after a LOCA

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12
Q

How does the RCS interface with the NA system?

A

powers reactor coolant pumps

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13
Q

How does the RCS interface with the IA system?

A

supplies control air to the pressurizer spray valves, controlled bleed-off containment isolation valves, and RDT bleed-off isolation valves

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14
Q

How does the RCS interface with the SG (main steam) and FW (feed water) systems?

A

remove heat from RCS

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15
Q

How does the RCS interface with the SS (primary sampling) system?

A

samples PCS loop 1 hot leg, surge line, and pressurizer steam space

used for chemistry and boron control

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16
Q

How does the RCS interface with the SE (Ex-core neutron monitoring)system?

A

monitors neutron flux from detectors outside the vessel

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17
Q

How does the RCS interface with the reactor vessel level monitoring system (RVLMS)/QSPDS (SH)?

A

provides reliable (class) indication of the vessel level online and during accidents

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18
Q

What is the purpose of the reactor vessel?

A

contains the core and vessel internals

directs flow of coolant through the core

part of RCS pressure boundary to prevent fission product release

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19
Q

What are the internals of the reactor vessel?

A

core support barrel assembly and the upper guide structure assembly

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20
Q

In the reactor vessel, what allows for radial and axial expansion of the core?

A

the core support barrel assembly

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21
Q

What components make up the core support barrel assembly?

A

Core support barrel

lower support structure and instrument nozzle assembly

core shroud assembly

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22
Q

In the reactor vessel, what supports the upper ends of the fuel assemblies and protects the CEAs from coolant cross flow?

A

the upper guide structure assembly

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23
Q

What components make up the upper guide structure assembly?

A

CEA shroud assembly

upper guide structure support barrel

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24
Q

What is the main flow path of the coolant within the reactor vessel?

A

through inlet nozzles, down between vessel wall and core barrel, through flow skirt section and into lower plenum, up through core to outlet region, through CEA shroud tubes and through outlet nozzles

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25
Q

In the reactor vessel, what purpose does the core bypass flow serve?

A

prevents stagnation of water in low flow areas

keeps primary coolant below saturation temp

removes gamma radiation heat from core support barrel

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26
Q

What do the surveillance capsule assemblies do?

A

monitor radiation induced changes in vessel materials

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27
Q

How many CEA’s are in the core?

A

89 total

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28
Q

What are the three types of CEAs and how many are there of each?

A

5 regulating groups (1, 2, 3, 4, 5)

2 shut down groups (A and B)

2 part strength groups (P1 and P2)

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29
Q

What are CEA pellets made of?

A

Boron Carbide

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30
Q

There are 48 of which CEAs?

A

12 finger full strength

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31
Q

There are 28 of which CEA’s?

A

four finger full strength

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32
Q

There are 13 of which CEA’s?

A

four finger part strength

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33
Q

How many Fuel assemblies do the 12 finger CEAs interact with?

A

5

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34
Q

How many fuel assemblies do the four finger CEAs interact with?

A

1

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35
Q

Which type of CEA do the shutdown banks A and B use?

A

12 finger only

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36
Q

Which type of CEA do the regulating groups use?

A

12 and 4 finger

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37
Q

What are the major components of the fuel assemblies?

A

fuel spacer grids

upper end fitting

hold down plate

lower end fitting

guide tubes

fuel rods

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38
Q

describe the construction of a fuel rod

A

filled with uranium pellets with a compression spring and spacer disks at each end of a zirconium alloy tube seal welded with end caps and pressurized with helium

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39
Q

Why are fuel rods pressurized with helium?

A

improve thermal conductivity of pellet to clad gap

prevent clad collapse

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40
Q

Why are the fuel pellets “dished” at the ends?

A

account for thermal expansion and fuel swelling

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41
Q

What maintains the RCS in a sub-cooled condition?

A

the pressurizer

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42
Q

What acts as a surge volume to minimize pressure changes during load transients?

A

pressurizer

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43
Q

What prevents the RCS from over pressurizing?

A

the pressurizer

44
Q

What is the RCS safety limit pressure?

A

2750

45
Q

what is the normal RCS pressure?

A

2250

46
Q

What do the four spring loaded safety valves on the pressurizer do?

A

prevent the RCS from reaching safety limit pressure

47
Q

Where do the four safety valves discharge to?

A

under the water line in the RDT (reactor drain tank)

48
Q

What happens if the RDT (reactor drain tank) is over pressurized by up to 10 psi? Over 10 psi?

A

tank reliefs to gaseous radwaste

tank relieves to containment through a rupture disk

49
Q

What is the purpose of the pressurizer heaters?

A

to boil the water to increase the mass of steam in the vapor space

50
Q

How many pressurizer heaters are there? How many banks are they divided into?

A

36

8

51
Q

How many of the pressurizer heater banks are back ups? How many proportional banks are there?

A

6

2

52
Q

How many heaters are in the proportional pressurizer heater banks?

A

3 each

53
Q

How many heaters are in the back up pressurizer heater banks?

A

banks B1 and B2 each have 3

banks B3, 4, 5, and 6 all have 6 heaters each

54
Q

How many kW are each of the pressurizer heaters rated at?

A

50

55
Q

How can the pressurizer heaters be controlled?

A

automatically by the pressurizer pressure control system

manually by operator

56
Q

Where are the pressurizer heaters powered from?

A

two back up banks are class powered from PGA/PGB

all other heaters are powered from NG

57
Q

What is the purpose of the pressurizer spray system?

A

to reduce pressure by condensing steam in the vapor space of the pressurizer using subcooled water

58
Q

Describe Main spray in the pressurizer

A

subcooled water is supplied from the cold leg of the reactor

flow is controlled by diaphragm valves

59
Q

What pressures are associated with the main spray flow control valves?

A

start to open at 2275

full open at 2300

60
Q

describe auxiliary spray in the pressurizer

A

water supplied from charging pumps

two solenoid valves to control flow

61
Q

Why is Aux spray more effective than main spray?

A

charging water is 110* less than cold leg temp (555*).

62
Q

How many spray heads are there for main spray and aux spray?

A

they share one spray head

63
Q

Where does the pressurizer surge line connect the pressurizer to?

A

loop 1 hot leg

64
Q

What is the purpose of the pressurizer surge line?

A

flow path for coolant surging to or from pressurizer

transmits pressurizer pressure to entire RCS

65
Q

How is main spray bypass flowrate controlled?

A

manually adjusted to establish a temp differential of less than 70* between cold leg and spray nozzle piping

66
Q

Why won’t the main spray flow function without the RCPs in service?

A

reactor vessel differential pressure isn’t sufficient to maintain spray flow without the RCPs

67
Q

why is maintaining constant main spray valve bypass flow important?

A

minimizes thermal shock on pipes, valves and spray nozzle

minimizes thermal stratification in piping

keeps chemistry uniform throughout RCS and pressurizer

68
Q

If the pressurizer spray valve bypass valves are NOT isolation valves, what are they?

A

metering valves

69
Q

Describe the sealing mechanism between the reactor vessel and the closure head.

A

two silver plated inconel, self- energizing, metal O-rings sit in machined grooves on the closure head flange.

the outer o-ring is passive until the inner o-ring fails

70
Q

In reference to the reactor vessel head, what is a self-energizing o-ring?

A

the O-rings are drilled around the inside allowing RCS pressure to pressurize the o-ring and form the seal

71
Q

What is the reactor vessel head seal drain valve? Where does it drain to?

A

When the inner reactor head o-ring starts leaking, causing an increase in pressure between the O-rings, this valve drains the coolant between the O-rings

RDT

72
Q

What two sections of the steam generator interfaces with the RCS?

A

primary chamber

tube sheet and U-tubes

73
Q

Where is the primary chamber located in the steam generator and what is its purpose?

A

its in the bottom of the steam generator

part of the RCS boundary and directs flow through the steam generator

74
Q

What is the design pressure and temperature of the steam generator primary chamber?

A

650*F

2500 PSI

75
Q

What is the purpose of the steam generator tube sheet and U-tubes? How thick is the tube sheet?

A

separate primary from secondary sides of the steam generator

permit heat removal from the primary side without radioactive material transfer

23.5”

76
Q

What is the difference between a steam generator tube rupture and a primary leakage?

A

S/G tube rupture is when the tube penetration is bad enough that the CVCS can’t maintain pressurizer level

primary leakage is when the CVCS can maintain pressurizer level

77
Q

Why is a steam generator tube rupture bad?

A

reactor coolant would be leaking into the main steam system allowing passage of radioactive material

78
Q

What are the primary functions of the reactor coolant pumps?

A

RCS boundary

provide flow in RCS

add heat to primary loop during plant heat ups

provide motive force for main spray valves

79
Q

Are the reactor coolant pumps powered from class or non-class ?

A

non-class

80
Q

What is the purpose of the RCP oil lift system?

A

provides forced lubrication to the thrust bearing

81
Q

How long before an RCP start is its respective oil lift pump started and why? how long after start up will the oil lift pump run?

A

7 minutes before so the oil can push the thrust bearing pads away from the thrust runner

2 after

82
Q

What components make up the RCP oil lift system?

A

oil reservoir, filter, accumulator and oil lift pump

83
Q

What is the RCP oil lift pump auto feature?

A

prior to stopping RCP, oil lift pump handswitch must be put to auto–

RCP will stop, oil pump will turn on until operator secures handswitch

84
Q

What minimizes leakage along the RCP shaft, also being an RCP boundary?

A

shaft seal assembly

85
Q

What components make up the RCP shaft seal assembly?

A

casing, three tandem mechanical pressure reduction seals, auxiliary impeller

86
Q

What system injects water at 6.6 gpm to the RCP shaft seal assembly?

A

charging

87
Q

What is the total flow through the RCP shaft seal assembly?

A

22.6 gpm

88
Q

In the RCP shaft seal assembly, where does majority of the seal water flow get routed to?

A

through the auxiliary impeller to the journal bearing and lower journal bearing cavity

89
Q

In the RCP shaft seal system, what is the pressure drop across each of three seals?

A

42% of system pressure for first two seals, 16% across third seal

90
Q

In the RCP shaft seal system, where is leakage past the vapor seal directed to?

A

Reactor Drain Tank

91
Q

Will the seal bleedoff isolation valves close while the RCP is running?

A

no

92
Q

What is the purpose of the RCP motor flywheel?

A

increases rotating inertia of the RCP which increases coast down time during LOP to pump motors

93
Q

What is the purpose of the anti-reverse rotation device?

A

stops a pump when it reaches zero speed so it can withstand reverse torques

94
Q

Name the start permissives of the RCPs.

A

no motor fauls

oil lift flow

NC water flow

RCP seal bleed off valve full open

95
Q

What are the RCP trips?

A

under-voltage

over-current

coast-down

less than 600 for a few seconds during start up

96
Q

What is the tech spec limit for RCS pressure?

A

2750 psia

97
Q

What is the tech spec range for pressurizer pressure?

A

2130-2295 psia

98
Q

What is the tech spec Tcold RCS loop temperature limit?

A

545*F

99
Q

Per tech spec, in mode 1 and 2, how many RCS loops have to be OPERABLE and in operation?

A

two

100
Q

Per tech spec, in mode 3, how many RCS loops must be OPERABLE and in operation?

A

1

101
Q

Per tech specs, in mode 4, how many SDC loops must be OPERABLE? How many in operation?

A

2

1

102
Q

Per tech spec, How many pressurizer safety valves must be OPERABLE with lift settings between 2450-2549 psia

A

4

103
Q

What is the heat sink to the RCS under normal operations?

A

Main steam and main feedwater systems

104
Q

Where can I get samples of the RCS?

A

Loop 1 hot leg

Surge line

Pressurizer steam space

105
Q

What affect does the data collected from the surveillance capsule assemblies have on the plant?

A

Can have an effect on allowable heat up and cool down rates and the minimum temperature for reactor vessel pressurization

NLO Systems 2023 (67 decks)

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