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NLO Systems > RC- Reactor Coolant System > Flashcards

RC- Reactor Coolant System Flashcards

1
Q

What are the six main purposes of the RCS?

A

1) transfer thermal energy to the S/G in form of steam to produce power

2) secondary barrier to prevent the release of fission products

3) provide core cooling during all normal plant conditions (except shutdown cooling

4) coolant circulation of boron and lithium concentration (increase pH prevent corrosion)

5) control pressurizer level & pressure

6) RC gas vent to remove gas from pressurizer and reactor head post-accident

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2
Q

How does the RCS interface with the CEDMCS system?

A

CEDMCS controls the position, direction, rate, and duration of CEA’s in reactor vessel

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)? (EXPLANATION Question)

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? (EXPLANATION Question)

A

nothing. it only collects data

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6
Q

How does the RCS interface with the CH system?

A

Letdown maintains pressurizer level & purification

Charging maintains pressurizer level & provides for RCS seal injection + aux spray header (when normal spray to pressurizer is unavailable)

Charging header is for chemistry control

CVCS maintains boron concentration (increases pH, and reduces reactivity) & collects drainage of RCS in RDT

RCS pump seal bleedoff goes to VCT or alt. RDT

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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

NC provides cooling to the RCP Hx (priority load):
motor air cooler
Motor lube oil cooler
Pump thrust bearing cooler
HP + LP seal coolers

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9
Q

How does the RCS interface with the SI system?

A

SI: injects borated water into RC for emergency core cooling after ESFAS signal activation

SDC: reactor coolant is cooled by shutdown cooling to bring Hot Standby (350F) —> Cold Standby (<135F)

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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 injection of borated water cooling?

A

after a LOCA (loss of cooling accident)

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12
Q

How does the RCS interface with the 13.8 kV NA system?

A

Supply power for RCPs

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13
Q

How does the RCS interface with the IA system?

A

Pneumatic main spray valves of IA system 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 by transferring it to secondary system via SG

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15
Q

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

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? (EXPLANATION Question)

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)? (EXPLANATION Question)

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 (which support fuel, CEA, in-core)

Absorb static + dynamic loads & transmit to vessel

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
-lower support structure
-In-core instrumentation nozzle assembly
-upper guide structure assembly
-core shroud
-fuel + fuel rods
-fuel assembly
-CEA
-burnable poison rods
-reactor vessel head

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20
Q

In the reactor vessel, what allows for radial and axial expansion of the core? (EXPLANATION Question)

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 (sub-cooled)

removes gamma radiation heat from core support barrel

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26
Q

What do the surveillance capsule assemblies do? (EXPLANATION Question)

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? (EXPLANATION Question)

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

neutron absorbing pellets (Boron Carbide)

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30
Q

There are 48 of which CEAs?

A

12 finger full strength poison rods

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31
Q

There are 28 of which CEA’s?

A

four finger full strength poison rods

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32
Q

There are 13 of which CEA’s?

A

four finger part strength poison rod

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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? (EXPLANATION Question)

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/deformation

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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

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44
Q

What is the RCS safety limit pressure?

A

2750 psia

45
Q

what is the normal RCS pressure?

A

2250 psia

46
Q

What do the four 6” spring loaded safety valves on the pressurizer do?

A

Over-pressure protection valves lift at 2475 psia to prevent the RCS from reaching safety limit pressure (limit of 110% design pressure 2250 psig) after a complete loss of Main Turbine Generator load without simultaneous reactor trip

47
Q

Where do the four safety valves discharge to?

A

under the water line in the RDT (reactor drain tank) where steam is released under water to be condensed and cooled/quenched

48
Q

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

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 of pressurizer

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 (4 non-class + 2 class)

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 (based on set point entered by RO

-manually remotely by Control Room operator
-manually locally by AO by directly opening breaker during loss of Control Power

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 loop 1 cold legs (1A, 1B) of the reactor

flow is controlled by diaphragm operated globe valves to control spray valves

Each spray control valves had 1” bypass valve that is opened during normal operations for small continuous spray

59
Q

What pressures are associated with the main spray flow control valves? (EXPLANATION Question)

A

start to open at 2275

full open at 2300

60
Q

describe auxiliary spray in the pressurizer

A

water supplied from charging pumps (CVCS) to provide sufficient differential pressure across vessel for pressurizer main spray flow

Mainly used during plant heat up, or to allow cooldown if RCP are shutdown

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

1 shared 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

12” pipe connecting 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

Bypass flow 475 gpm

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 (redundancy, 100% capacity)

-pressure sensors installed downstream to detect leakage past inner o-ring

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, inflating o-ring improves 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 inlet nozzles —>inner plenum where transfers heat to secondary water, then flows out of U-Tube into outer plenum —> RC flows out SG outlet nozzles into cold legs of each loop

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 13.8 kV (NA) system

80
Q

What is the purpose of the RCP oil lift system?

A

During RCP startup/stop:
provides forced lubrication to the thrust bearing 5gpm of oil at 3000 psig to the upper bearings

During RCP trip:
Auto starts to maintain LO circulation for lubrication and cooling as RCP spins down

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

De-energizes 2 min time delay after RCP start

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

20 gpm through the auxiliary impeller to the journal bearing and lower journal bearing cavity provides cooling and lubrication

2.6 gpm through seal cavity #1 and #1 seal cooler as seal bypass flow

89
Q

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

A

1st drop: 2250 psia —> 1300 psia

2nd drop: 1300 psia —> 300 psia

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 fault

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 trip signal after 20 sec due to LOOP

Speed <600 rpm after 14 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

106
Q

When will backup heater automatically energize?

A

-pressurizer <2200 psia
-pressurize level is >set point level (to minimize effect when steam demand changes cause level to lower and CVCS restores it —> causing in-surge of cold water to pressurizer which decrease bulk water and lower pressure)

107
Q

What is power supply of lift oil pump?

A

Non-class 480 VAC MCC (NH)

108
Q

What cools the RCP?

A

Nuclear Cooling Water

1st nuclear cooling water line is routed to motor air coolers and motor lube oil coolers

2nd nuclear cooling water line cools pump high pressure seal cooler, pump #1 and #2 seal coolers and pump thrust bearing lube oil cooler

109
Q

What is power supply for RCP solenoid valves?

A

Class 125 VDC (PK) system

NLO Systems (66 decks)

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