Service Gases-Nitrogen Flashcards
What is nitrogen used for at the plant ?
Used for:
-Blanketing
-Pressurizing
-purging
-Backup for various systems
What pressure does nitrogen system supply nitrogen at ?
High pressure-650 psig
Low pressure -115psig
What systems or components uses High Pressure Nitrogen for Pressurizing ?
-Safety Injection Tanks(STIs)
-Atmospheric Dump Valves(ADV)accumulator
-SG Downcomer Feedwater Isolation Valves(FWIV) &Control Valves Accumulator
What system uses High Pressure Nitrogen to open?
Downcomer Feedwater Isolation Valves(FWIVs)
What components use High Pressure Nitrogen as backup to Instrument Air for Operating ?
-Atmospheric Dump Valves(ADVs)
-Downcomer Feedwater Control Valves
-Downcomer Feedwater Isolation Valves(FWIVs) Pneumatic Positioning Valve
What surge tanks does Low Pressure Nitrogen blanket ?
-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)
What storage/drain tanks does Low Pressure Nitrogen Blanket ?
-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
What systems uses Low Pressure Nitrogen Purging ?
-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
What does Low Pressure Nitrogen serve as backup for ?
Serves as a backup to Instrument Air (AI)supply header
What’re the major components of the Nitrogen System ?
-Liquid Nitrogen Storage Tank
-Two Liquid Nitrogen Pumps
-Low Pressure Nitrogen Vaporizer
-High Pressure Nitrogen Vaporizer
-Nitrogen Gas Storage Cylinder
-Regulating Valves
What is flow path for Low Pressure Nitrogen ?
1.)Storage Tank
2.)LP Ambient Vaporizer
3.)LP Header
4.)Flow through 1of2 PCV/regulating valve
5.)LP header loads
What is the normal and backup pressure for LP header loads?
Normally-115psig
Backup-105psig
What is flow path for High Pressure Nitrogen ?
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
What is Liquid Nitrogen Storage Tank used for ?
-Used to storage Nitrogen for LP and HP headers
-Storage Capacity designated to provide adequate to permit refueling shutdown and subsequent starts
What is the net Capacity & what is the pressure that the Liquid Nitrogen Storage Tank is kept at ?
Net capacity- 3082Gallons but is maintained @85% full
Pressure- rated for 245psig but is maintained @ 150-160psig
What is the inner and outer cylinder designed for in the Liquid Nitrogen Storage tank ?
Space between inner and outer cylinder is maintained at vacuum and filled with insulation to help maintain pressure inside tank
How often is Liquid Nitrogen storage tank refilled ?
-Filled twice per week from trailer while at power, or as needed during outage
-Top fill valve & Bottom fill valve
When being refilled what pressure is tank supposed to be maintained at ? How full should it be filled ?
-Tank should be maintained between 150-160psig
-Should be filled to 85% full(where tank liquid overflow line is)
What happens when tank is refilled via bottom valve ?
Causes tank pressure and level to rise
What happens when filling tank via Top fill line ?
-Spray valve causes gas at top of tank to condense and lower pressure and raise level
What happens if Nitrogen Storage Tank level drops below 150psig ?
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
What happens when Nitrogen Storage Tank Pressure raises above 160 psig ?
Tank Vapor Space Back-pressure Control Valve opens, bleeds gas from top of tank to liquid supply line to LP vaporizer, lowers tank pressure
What is safety relief valve pressure set-point for Nitrogen Storage tank ?
-Safety Relief Valve pressure setpoint is 245psig
-Rupture disc for protection from over pressurization due to excess liquid vaporization
What is maximum tank operating pressure? What happens if that pressure is exceeded?
-Max. Operating pressure is 220psig
-If 220psig is exceeded AO must manually vent tank to lower pressure
What does Liquid Nitrogen Control Panel do for Nitrogen system ?
-Provides controls, indications, and alarms for HP Liquid Nitrogen Pumps & associated solenoid operated valves
What does PLC do for nitrogen system ? What’re the two types of PLCs between the 3 units ?
-PLC monitors and actuates in High Pressure Nitrogen system
Two types of PLC:
-Modicron Programmable Logic Controller
-Allen-Bradley Programmable Logic Controller
What do the PLCs monitor ?
-Liquid nitrogen storage tank level
-HP Nitrogen Header temperature downstream of vaporizer
-HP Nitrogen Active Bank pressure
What is the Two position(On/Off) Main Power switch used for ?
It gives power to Control Panel and PLC
What is the Two Position selector switch(A/B) pump for ?
-Provided to select which HP Liquid Nitrogen Pump to be in service
-The selected pump will energize on a start signal
What is Start Pushbutton for ?
One start Pushbutton is provided to start selected HP liquid Nitrogen Pump
What is Override Pushbutton used for ?
Provided to override automatic operation of controller and manually start HP Liquid Nitrogen Pump
What light indications are provided for the pump ?
-‘A’ pump running
-‘B’ pump running
-Pump standby
-Cooldown
-Pump override
What alarm indications and controls does the Liquid Storage Tank Provide ?
-Low level in tank
-Low temp. In the HP Header between HP Vaporizer and Storage Banks
-High Pressure in Active Bank
What cools the PLC inside the control panel ?
Small amount of nitrogen pulled out of LP header, which goes through PCV, then to the Control Cabinet & PLC
What’re the High Pressure Liquid Nitrogen pumps used for ?
Transfer liquid Nitrogen from storage tanks to HP vaporizers, which is then stored in HP Nitrogen storage banks
What kinds of pumps are the HP Liquid Nitrogen pumps?
Reciprocating positive displacement pumps
When will the PLC send a start signal to the standby HP Nitrogen Pump ?
When HP Nitrogen Bank drops to 1400psig it’ll send a start signal to standby pump
How would you manually start pump if Active Bankpressure is between 1400psig-2100psig ?
1.)Push override button,which will illuminate override light
2.) Push start Pushbutton to send start signal to pump
Which solenoid valve opens when the HP nitrogen pumps receive a start signal ?
The Solenoid operated Inlet Valve opens to allow flow from liquid nitrogen storage tank to the HP pumps
What happens as liquid nitrogen is introduced to the warm HP pump suction piping & the pump itself ?
Initially the nitrogen will flash to vapor
How is the Nitrogen that has flashed to vapor in the HP pump suction piping removed?
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
How long does system remain in static state for pump suction line and pump itself ? What happens after 15 minutes ?
-Will stay in static state for 15 mins for cooldown
-After 15 mins cooldown light will turn off and pump will start
What happens to Vapor Return Solenoid Valves after 15 seconds of pump starting ?
Solenoid valves will shut after 15 seconds
When will solenoid inlet valves shut ?
When the active bank reaches 2100psig, which will turn off pump and will shut solenoid inlet valves
What conditions will automatically stop the Liquid Nitrogen Pumps?
-Low temp down stream of HP vaporizer
-High pump discharge pressure at 2400psig
-Liquid Nitrogen Storage Tank Low Levels at 25 inches
Why does low temp downstream of High Pressure Vaporizer auto trip HP liquid nitrogen pump ?
-Prevents liquid carryover into High Pressure Storage Banks
-Prevents lifting of safety relief valves & protects from over-pressurization
Why will Low Level in Liquid Nitrogen Storage (25in), auto trip HP liquid nitrogen pump ?
Prevents pump from cavitation and low suction pressure
What’re the LP/HP Nitrogen Vaporizers used for ?
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
How does LP ambient vaporizer work ?
-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
How does HP Nitrogen Vaporizer work ?
-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
What’s the capacity of the HP Nitrogen Gas?
Capacity is sized for 7days at normal usage
How many cylinders do the two nitrogen gas storage banks hold ?
Storage bank capacity is evenly divided between two banks, each containing 4 cylinders
What features does the Nitrogen Gas Storage Banks have ? What does each cylinder have ?
-Isolation valve
-Pressure relief valve
-Temperature indication
-Pressure indication
Cylinder:
-individual isolation valves
-Rupture discs
What’re the cylinders normally pressurized at ?
-Pressurized between 1400psig-2100psig
-High or Low pressure in active bank causes alarm in control room
What’re other ways Nitrogen Storage Banks can be pressurized from besides HP Liquid Nitrogen Pumps?
Banks can also be pressurized from trailer truck stanchion
When HP Active Bank drops to 1400psig, how does HP liquid nitrogen pumps react ?
1.)Pumps cooldown
2.)Starts
3.)Pumps nitrogen from storage tank
4.) Through HP Vaporizer
5.) To refill active/reserve banks to 2100psig
Where does the HP nitrogen go from the active /reserve banks ?
Goes to HP header,which will supply nitrogen through associated PCV/PRV pairs to the loads
What’re the PCV/PRV used for on the Nitrogen system ?
Work together to accommodate inlet temperature fluctuations with a steady input pressure
What’re the PCV used for in the Atmospheric Dump Valves(ADV)Accumulators ?
Used to maintain pressure inside ADV Accumulators above setpoint at 635psig, but below top of instruments indicating range of 700psig
What pressure does the Active Bank PRV have to be maintained at ?
Maintains HP header usually between 650-680psig read on local pressure gauge
What pressure does the Reserve bank PRV maintain HP header at ?
Maintained at 630psig
When starting system why should you not adjust reserve bank PCV when pressures are set ?
You won’t be able to tell a difference in gauge, because Active bank is at a higher pressure than the reserve bank
What is the low pressure PCV/PRV backup ?
PCV/PRV supplies nitrogen from high pressure header to the low pressure header at 100psig in event of loss of low pressure header supply
What do Low and High pressure supply lines that penetrate containment have to be able to isolate ?
They have Solenoid operated Containment Isolation Valves
What will cause Containment Isolation Valves to automatically close ?
-Containment Isolation Actuation Signal(CIAS)
-Loss of power to the solenoid
How does Nitrogen system interface with NH system ?
-NH provides power to Liquid Nitrogen Control Panel
-NH provides power to the HP Liquid Nitrogen Pumps
How does Nitrogen interface with PK system ?
PK system provides power to solenoid operated Containment Isolation Valves
How does Nitrogen interface with a Condensate(CD) ?
Low pressure nitrogen injected into Main Condenser to purge oxygen & non-condensable gases via Condenser Air Removal system(AR)
What tanks from Chemical & Volume Control receives a cover gas from Nitrogen system for which tanks?
-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
What tanks from Chemical & Volume Control receives a Purging Gas from Nitrogen system for which tanks?
-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
How does nitrogen system interface with Condensate Transfer& Storage(CT)?
Nitrogen is used as cover gas for CT tank
How does Nitrogen system interface with Demineralized Water(DW)
Nitrogen provides a cover gas for DW tank
How does Nitrogen interface with Essential Chilled Water(EC)?
Nitrogen provides cover gas for EC Expansion Tanks
How does Nitrogen interface with Extraction Steam & Drain(ED)?
ED system receives LP nitrogen gas purging and blanketing the FW heaters while shutdown
How does Nitrogen interface with Essential Cooling Water(EW)?
Nitrogen provides cover gas for EW tanks
How does Nitrogen interface with Gaseous Radwaste(GR)system ?
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
How does LP Nitrogen interface with Instrument & Service Air(IA)?
-IA system receives LP nitrogen as a backup to the IA supply header
What happens if Instrument& Service Air header pressure drops to 85psig what will happen ?
Nitrogen will automatically be supplied to IA header to maintain its pressure
How does High PressureNitrogen interface with Instrument & Service Air ?
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
How does Nitrogen system interface with Liquid Radwaste(LR)?
LR system receives nitrogen for purging of the LR evaporator
How does Nuclear Cooling Water(NC) interface with Nitrogen ?
NC surge tank used Nitrogen as a cover gas
What conditions does steam generator(SG)use nitrogen as a cover gas ?
Uses nitrogen as cover gas during wet layup conditions
Why is High Pressure Nitrogen regulated down 240psig for use on SG system ?
-240psig to open Downcomer Feedwater Isolation Valve(FWIVs)
Why is High Pressure Nitrogen regulated down 115psig for use on SG system ?
115psig used to operate equipment following loss of Instrument air:
-Pneumatic positioning on Downcomer FWIVS
-Downcomer Feedwater Control Valves
Why is High Pressure Nitrogen regulated down 100psig for use on SG system ?
100psig is used to operate Atmospheric Dump Valves(ADVs)
Why is High Pressure Nitrogen needed for pressurizing on SG system ?
-Pressurized Atmospheric Dumb Valve(ADV)Accumulators
-Used for 16hour coping time for operating ADVs during Station Blackout for safe shutdown cooling
How are Downcomer Feedwater Isolation Valves and Control Valve Accumulator operated, on loss of Instrument Air AND High pressure nitrogen ?
They’re operated from stored high pressure nitrogen in accumulator
What pressure does High Pressure nitrogen coming out of accumulator have to be when opening Downcomer Feedwater Isolation Valves ?
Pressure control valve is set at 240psig to open Downcomer Feedwater Isolation Valves FWIVs
What is pressure set at coming out of accumulator to pneumatically position FWIVs & Downcomer Feedwater Control valve ?
Pressure control valve set at 115psig
How does nitrogen interface with RCS?
High pressure nitrogen used to sweep pressurizer during depressurization and cooldown
How does Safety Injection interface with Nitrogen ?
Nitrogen pressurizes Saftey Injection Tanks(SITs) to support passive injection of borated water into reactor following depressurization of reactor coolant system
How does Nitrogen interface with Turbine Cooling water(TC) ?
TC surge tank uses nitrogen as cover gas
How does Normal Chilled Water (WC) interface with Nitrogen ?
WC surge tank uses nitrogen as cover gas
What happens when instrument air header drops to 85psig ?
Solenoid Nitrogen Backup Valve will automatically open to allow Low Pressure Nitrogen in to repressurize header
What happens when a Solenoid Operated Nitrogen Backup Valve is opened, on low instrument air pressure ?
-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
What happens if Instrument Air (AI)is lost to Downcomer Feedwater Isolation Valves(FWIVs) ?
High Pressure nitrogen will be aligned by a PCV set at 115psig to operate FWIV positioning valve, which allows FWIV to be opened
What happens if LP Nitrogen is lost for an extended period of time ?
Cover gases on surge tanks would fade away causing corrosion in systems
What happens if Low Pressure Nitrogen & Instrument Air is lost at the same time ?
Since nitrogen is backup for instrument air, plant would have to shutdown due to no valve control
What happens if High Pressure Nitrogen is lost for extended amount of time ?
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
