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Service Gases-Nitrogen Flashcards

1
Q

What is nitrogen used for at the plant ?

A

Used for:
-Blanketing
-Pressurizing
-purging
-Backup for various systems

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2
Q

What pressure does nitrogen system supply nitrogen at ?

A

High pressure-650 psig
Low pressure -115psig

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3
Q

What systems or components uses High Pressure Nitrogen for Pressurizing ?

A

-Safety Injection Tanks(STIs)
-Atmospheric Dump Valves(ADV)accumulator
-SG Downcomer Feedwater Isolation Valves(FWIV) &Control Valves Accumulator

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4
Q

What system uses High Pressure Nitrogen to open?

A

Downcomer Feedwater Isolation Valves(FWIVs)

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5
Q

What components use High Pressure Nitrogen as backup to Instrument Air for Operating ?

A

-Atmospheric Dump Valves(ADVs)
-Downcomer Feedwater Control Valves
-Downcomer Feedwater Isolation Valves(FWIVs) Pneumatic Positioning Valve

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6
Q

What surge tanks does Low Pressure Nitrogen blanket ?

A

-Turbine Cooling surge tank(TC)
-Nuclear Cooling surge tank(NC)
-Essential Cooling surge tank (EW)
-Essential Chilled surge tank (EC)
-Norm. Chilled surge tank(WC)

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7
Q

What storage/drain tanks does Low Pressure Nitrogen Blanket ?

A

-Condensate Storage Tank(CST)
-Demon. Water Storage Tank(DWST)
-Equipment Drain Tank
-Reactor Drain Tank
-Volume Control Tank(VCT)
-Boric Acid Concentrator(BAC)
-Steam Generators

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8
Q

What systems uses Low Pressure Nitrogen Purging ?

A

-Volume control tank
-CVCS gas stripper
-Liquid Rad. Waste Evaporator (LRS)
-Boric Acid Concentrator Vent Cooler (BAC)
-Reactor Coolant System pressurizer
-Equipment Drain Tank(EDT)
-Reactor Drain Tank(RDT)
-Main Condenser
-Feedwater Heaters

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9
Q

What does Low Pressure Nitrogen serve as backup for ?

A

Serves as a backup to Instrument Air (AI)supply header

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10
Q

What’re the major components of the Nitrogen System ?

A

-Liquid Nitrogen Storage Tank
-Two Liquid Nitrogen Pumps
-Low Pressure Nitrogen Vaporizer
-High Pressure Nitrogen Vaporizer
-Nitrogen Gas Storage Cylinder
-Regulating Valves

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11
Q

What is flow path for Low Pressure Nitrogen ?

A

1.)Storage Tank
2.)LP Ambient Vaporizer
3.)LP Header
4.)Flow through 1of2 PCV/regulating valve
5.)LP header loads

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12
Q

What is the normal and backup pressure for LP header loads?

A

Normally-115psig
Backup-105psig

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13
Q

What is flow path for High Pressure Nitrogen ?

A

1.)Liquid Nitrogen from storage tank to liquid Nitrogen pumps
2.)HP Ambient Vaporizer
3.)Storage Banks
4.)Each Storage supplies one set of PCV/PRV to maintain HP header
-Active Bank :650psig
-Reserve Bank :630psig

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14
Q

What is Liquid Nitrogen Storage Tank used for ?

A

-Used to storage Nitrogen for LP and HP headers
-Storage Capacity designated to provide adequate to permit refueling shutdown and subsequent starts

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15
Q

What is the net Capacity & what is the pressure that the Liquid Nitrogen Storage Tank is kept at ?

A

Net capacity- 3082Gallons but is maintained @85% full
Pressure- rated for 245psig but is maintained @ 150-160psig

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16
Q

What is the inner and outer cylinder designed for in the Liquid Nitrogen Storage tank ?

A

Space between inner and outer cylinder is maintained at vacuum and filled with insulation to help maintain pressure inside tank

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17
Q

How often is Liquid Nitrogen storage tank refilled ?

A

-Filled twice per week from trailer while at power, or as needed during outage
-Top fill valve & Bottom fill valve

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18
Q

When being refilled what pressure is tank supposed to be maintained at ? How full should it be filled ?

A

-Tank should be maintained between 150-160psig
-Should be filled to 85% full(where tank liquid overflow line is)

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19
Q

What happens when tank is refilled via bottom valve ?

A

Causes tank pressure and level to rise

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20
Q

What happens when filling tank via Top fill line ?

A

-Spray valve causes gas at top of tank to condense and lower pressure and raise level

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21
Q

What happens if Nitrogen Storage Tank level drops below 150psig ?

A

Nitrogen Tank Buildup Regulator opens and Pressure Build Coil vaporizes portion of nitrogen and returns it to top of tank to buildup pressure between 150-160psig

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22
Q

What happens when Nitrogen Storage Tank Pressure raises above 160 psig ?

A

Tank Vapor Space Back-pressure Control Valve opens, bleeds gas from top of tank to liquid supply line to LP vaporizer, lowers tank pressure

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23
Q

What is safety relief valve pressure set-point for Nitrogen Storage tank ?

A

-Safety Relief Valve pressure setpoint is 245psig
-Rupture disc for protection from over pressurization due to excess liquid vaporization

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24
Q

What is maximum tank operating pressure? What happens if that pressure is exceeded?

A

-Max. Operating pressure is 220psig
-If 220psig is exceeded AO must manually vent tank to lower pressure

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25
Q

What does Liquid Nitrogen Control Panel do for Nitrogen system ?

A

-Provides controls, indications, and alarms for HP Liquid Nitrogen Pumps & associated solenoid operated valves

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26
Q

What does PLC do for nitrogen system ? What’re the two types of PLCs between the 3 units ?

A

-PLC monitors and actuates in High Pressure Nitrogen system
Two types of PLC:
-Modicron Programmable Logic Controller
-Allen-Bradley Programmable Logic Controller

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27
Q

What do the PLCs monitor ?

A

-Liquid nitrogen storage tank level
-HP Nitrogen Header temperature downstream of vaporizer
-HP Nitrogen Active Bank pressure

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28
Q

What is the Two position(On/Off) Main Power switch used for ?

A

It gives power to Control Panel and PLC

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29
Q

What is the Two Position selector switch(A/B) pump for ?

A

-Provided to select which HP Liquid Nitrogen Pump to be in service
-The selected pump will energize on a start signal

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30
Q

What is Start Pushbutton for ?

A

One start Pushbutton is provided to start selected HP liquid Nitrogen Pump

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31
Q

What is Override Pushbutton used for ?

A

Provided to override automatic operation of controller and manually start HP Liquid Nitrogen Pump

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32
Q

What light indications are provided for the pump ?

A

-‘A’ pump running
-‘B’ pump running
-Pump standby
-Cooldown
-Pump override

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33
Q

What alarm indications and controls does the Liquid Storage Tank Provide ?

A

-Low level in tank
-Low temp. In the HP Header between HP Vaporizer and Storage Banks
-High Pressure in Active Bank

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34
Q

What cools the PLC inside the control panel ?

A

Small amount of nitrogen pulled out of LP header, which goes through PCV, then to the Control Cabinet & PLC

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35
Q

What’re the High Pressure Liquid Nitrogen pumps used for ?

A

Transfer liquid Nitrogen from storage tanks to HP vaporizers, which is then stored in HP Nitrogen storage banks

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36
Q

What kinds of pumps are the HP Liquid Nitrogen pumps?

A

Reciprocating positive displacement pumps

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37
Q

When will the PLC send a start signal to the standby HP Nitrogen Pump ?

A

When HP Nitrogen Bank drops to 1400psig it’ll send a start signal to standby pump

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38
Q

How would you manually start pump if Active Bankpressure is between 1400psig-2100psig ?

A

1.)Push override button,which will illuminate override light
2.) Push start Pushbutton to send start signal to pump

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39
Q

Which solenoid valve opens when the HP nitrogen pumps receive a start signal ?

A

The Solenoid operated Inlet Valve opens to allow flow from liquid nitrogen storage tank to the HP pumps

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40
Q

What happens as liquid nitrogen is introduced to the warm HP pump suction piping & the pump itself ?

A

Initially the nitrogen will flash to vapor

41
Q

How is the Nitrogen that has flashed to vapor in the HP pump suction piping removed?

A

A solenoid operated valve in a return line is opened on a start signal to direct vapor from HP pump suction piping to Liquid Nitrogen Storage Tank

42
Q

How long does system remain in static state for pump suction line and pump itself ? What happens after 15 minutes ?

A

-Will stay in static state for 15 mins for cooldown
-After 15 mins cooldown light will turn off and pump will start

43
Q

What happens to Vapor Return Solenoid Valves after 15 seconds of pump starting ?

A

Solenoid valves will shut after 15 seconds

44
Q

When will solenoid inlet valves shut ?

A

When the active bank reaches 2100psig, which will turn off pump and will shut solenoid inlet valves

45
Q

What conditions will automatically stop the Liquid Nitrogen Pumps?

A

-Low temp down stream of HP vaporizer
-High pump discharge pressure at 2400psig
-Liquid Nitrogen Storage Tank Low Levels at 25 inches

46
Q

Why does low temp downstream of High Pressure Vaporizer auto trip HP liquid nitrogen pump ?

A

-Prevents liquid carryover into High Pressure Storage Banks
-Prevents lifting of safety relief valves & protects from over-pressurization

47
Q

Why will Low Level in Liquid Nitrogen Storage (25in), auto trip HP liquid nitrogen pump ?

A

Prevents pump from cavitation and low suction pressure

48
Q

What’re the LP/HP Nitrogen Vaporizers used for ?

A

LP Vaporizer- transform liquid nitrogen to LP gas for use in LP header
HP Vaporizer -Transforms liquid nitrogen to HP gas for use in HP header

49
Q

How does LP ambient vaporizer work ?

A

-Vertical convective heat exchanger that extracts heat from surrounding air which vaporizes the nitrogen flowing through fins
-Consists of number of individual vaporizers connected in parallel
-Vaporizers have finned tubes for more surface area

50
Q

How does HP Nitrogen Vaporizer work ?

A

-HP nitrogen flows passes through finned tubes, which is heated to vaporization by heat extracted from surrounding area by the finned tubes, then it’s directed to HP Nitrogen Storage Banks

51
Q

What’s the capacity of the HP Nitrogen Gas?

A

Capacity is sized for 7days at normal usage

52
Q

How many cylinders do the two nitrogen gas storage banks hold ?

A

Storage bank capacity is evenly divided between two banks, each containing 4 cylinders

53
Q

What features does the Nitrogen Gas Storage Banks have ? What does each cylinder have ?

A

-Isolation valve
-Pressure relief valve
-Temperature indication
-Pressure indication
Cylinder:
-individual isolation valves
-Rupture discs

54
Q

What’re the cylinders normally pressurized at ?

A

-Pressurized between 1400psig-2100psig
-High or Low pressure in active bank causes alarm in control room

55
Q

What’re other ways Nitrogen Storage Banks can be pressurized from besides HP Liquid Nitrogen Pumps?

A

Banks can also be pressurized from trailer truck stanchion

56
Q

When HP Active Bank drops to 1400psig, how does HP liquid nitrogen pumps react ?

A

1.)Pumps cooldown
2.)Starts
3.)Pumps nitrogen from storage tank
4.) Through HP Vaporizer
5.) To refill active/reserve banks to 2100psig

57
Q

Where does the HP nitrogen go from the active /reserve banks ?

A

Goes to HP header,which will supply nitrogen through associated PCV/PRV pairs to the loads

58
Q

What’re the PCV/PRV used for on the Nitrogen system ?

A

Work together to accommodate inlet temperature fluctuations with a steady input pressure

59
Q

What’re the PCV used for in the Atmospheric Dump Valves(ADV)Accumulators ?

A

Used to maintain pressure inside ADV Accumulators above setpoint at 635psig, but below top of instruments indicating range of 700psig

60
Q

What pressure does the Active Bank PRV have to be maintained at ?

A

Maintains HP header usually between 650-680psig read on local pressure gauge

61
Q

What pressure does the Reserve bank PRV maintain HP header at ?

A

Maintained at 630psig

62
Q

When starting system why should you not adjust reserve bank PCV when pressures are set ?

A

You won’t be able to tell a difference in gauge, because Active bank is at a higher pressure than the reserve bank

63
Q

What is the low pressure PCV/PRV backup ?

A

PCV/PRV supplies nitrogen from high pressure header to the low pressure header at 100psig in event of loss of low pressure header supply

64
Q

What do Low and High pressure supply lines that penetrate containment have to be able to isolate ?

A

They have Solenoid operated Containment Isolation Valves

65
Q

What will cause Containment Isolation Valves to automatically close ?

A

-Containment Isolation Actuation Signal(CIAS)
-Loss of power to the solenoid

66
Q

How does Nitrogen system interface with NH system ?

A

-NH provides power to Liquid Nitrogen Control Panel
-NH provides power to the HP Liquid Nitrogen Pumps

67
Q

How does Nitrogen interface with PK system ?

A

PK system provides power to solenoid operated Containment Isolation Valves

68
Q

How does Nitrogen interface with a Condensate(CD) ?

A

Low pressure nitrogen injected into Main Condenser to purge oxygen & non-condensable gases via Condenser Air Removal system(AR)

69
Q

What tanks from Chemical & Volume Control receives a cover gas from Nitrogen system for which tanks?

A

-Reacter Drain Tank (RTD) SHUTDOWN
-Equip. Drain Tank(EDT)SHUTDOWN
-Volume Control Tank(VCT)SHUTDOWN
-Boric Acid Concentrator(BAC) condenser Vent cooler SHUTDOWN
-Gas Stripper

70
Q

What tanks from Chemical & Volume Control receives a Purging Gas from Nitrogen system for which tanks?

A

-Volume Control Tank(VCT)while shutdown
-Reactor Drain Tank(RTD)while shutdown
-Equip. Drain Tank(EDT) while shutdown
-Boric Acid Concentrator(BAC)Condenser Vent Cooler during operation to purge oxygen and non-condensable gases

71
Q

How does nitrogen system interface with Condensate Transfer& Storage(CT)?

A

Nitrogen is used as cover gas for CT tank

72
Q

How does Nitrogen system interface with Demineralized Water(DW)

A

Nitrogen provides a cover gas for DW tank

73
Q

How does Nitrogen interface with Essential Chilled Water(EC)?

A

Nitrogen provides cover gas for EC Expansion Tanks

74
Q

How does Nitrogen interface with Extraction Steam & Drain(ED)?

A

ED system receives LP nitrogen gas purging and blanketing the FW heaters while shutdown

75
Q

How does Nitrogen interface with Essential Cooling Water(EW)?

A

Nitrogen provides cover gas for EW tanks

76
Q

How does Nitrogen interface with Gaseous Radwaste(GR)system ?

A

LP Nitrogen is provided to GR system for automatic system purging following detection of high oxygen level in hydrogen environment to prevent O2/H2 from reaching combustible level

77
Q

How does LP Nitrogen interface with Instrument & Service Air(IA)?

A

-IA system receives LP nitrogen as a backup to the IA supply header

78
Q

What happens if Instrument& Service Air header pressure drops to 85psig what will happen ?

A

Nitrogen will automatically be supplied to IA header to maintain its pressure

79
Q

How does High PressureNitrogen interface with Instrument & Service Air ?

A

HP nitrogen is used a backup to Instrument Air to operate:
-ADVs
-Downcomer Feed-water Control valves
-Downcomer Feedwater Isolation valves(FWIVs) Pneumatic positioning valve

80
Q

How does Nitrogen system interface with Liquid Radwaste(LR)?

A

LR system receives nitrogen for purging of the LR evaporator

81
Q

How does Nuclear Cooling Water(NC) interface with Nitrogen ?

A

NC surge tank used Nitrogen as a cover gas

82
Q

What conditions does steam generator(SG)use nitrogen as a cover gas ?

A

Uses nitrogen as cover gas during wet layup conditions

83
Q

Why is High Pressure Nitrogen regulated down 240psig for use on SG system ?

A

-240psig to open Downcomer Feedwater Isolation Valve(FWIVs)

84
Q

Why is High Pressure Nitrogen regulated down 115psig for use on SG system ?

A

115psig used to operate equipment following loss of Instrument air:
-Pneumatic positioning on Downcomer FWIVS
-Downcomer Feedwater Control Valves

85
Q

Why is High Pressure Nitrogen regulated down 100psig for use on SG system ?

A

100psig is used to operate Atmospheric Dump Valves(ADVs)

86
Q

Why is High Pressure Nitrogen needed for pressurizing on SG system ?

A

-Pressurized Atmospheric Dumb Valve(ADV)Accumulators

-Used for 16hour coping time for operating ADVs during Station Blackout for safe shutdown cooling

87
Q

How are Downcomer Feedwater Isolation Valves and Control Valve Accumulator operated, on loss of Instrument Air AND High pressure nitrogen ?

A

They’re operated from stored high pressure nitrogen in accumulator

88
Q

What pressure does High Pressure nitrogen coming out of accumulator have to be when opening Downcomer Feedwater Isolation Valves ?

A

Pressure control valve is set at 240psig to open Downcomer Feedwater Isolation Valves FWIVs

89
Q

What is pressure set at coming out of accumulator to pneumatically position FWIVs & Downcomer Feedwater Control valve ?

A

Pressure control valve set at 115psig

90
Q

How does nitrogen interface with RCS?

A

High pressure nitrogen used to sweep pressurizer during depressurization and cooldown

91
Q

How does Safety Injection interface with Nitrogen ?

A

Nitrogen pressurizes Saftey Injection Tanks(SITs) to support passive injection of borated water into reactor following depressurization of reactor coolant system

92
Q

How does Nitrogen interface with Turbine Cooling water(TC) ?

A

TC surge tank uses nitrogen as cover gas

93
Q

How does Normal Chilled Water (WC) interface with Nitrogen ?

A

WC surge tank uses nitrogen as cover gas

94
Q

What happens when instrument air header drops to 85psig ?

A

Solenoid Nitrogen Backup Valve will automatically open to allow Low Pressure Nitrogen in to repressurize header

95
Q

What happens when a Solenoid Operated Nitrogen Backup Valve is opened, on low instrument air pressure ?

A

-Control room alarm when opened
-Manual bypass valve is available if Nitrogen Backup valve fails to open
-Nitrogen backup valve automatically closes when IA header pressure reaches 105psig

96
Q

What happens if Instrument Air (AI)is lost to Downcomer Feedwater Isolation Valves(FWIVs) ?

A

High Pressure nitrogen will be aligned by a PCV set at 115psig to operate FWIV positioning valve, which allows FWIV to be opened

97
Q

What happens if LP Nitrogen is lost for an extended period of time ?

A

Cover gases on surge tanks would fade away causing corrosion in systems

98
Q

What happens if Low Pressure Nitrogen & Instrument Air is lost at the same time ?

A

Since nitrogen is backup for instrument air, plant would have to shutdown due to no valve control

99
Q

What happens if High Pressure Nitrogen is lost for extended amount of time ?

A

ADV accumulator will lose pressure and if pressure falls below 615psig(becomes inoperable), which will affect required 16 hour coping time for heat removal during station blackout

Systems (62 decks)

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