Reactor Coolant System Flashcards
What is main purpose of Reactor coolant system ?
-Transfer heat from core to SG to produce steam
-Serve as secondary barrier during a release of fission products
-provide sufficient core cooling during normal plant evolutions and transients to preclude fuel damage
How does CEDMCS interface with Reactor Coolant system ?
CEDMCS control direction,rate,& duration of CEA motion, automatically or manually
What is Fixed in-core instrumentation system(RI)?
-Measures Neutron flux & Coolant temperature at 61 different locations
-System information monitors core characteristics, Xenon and Power Peaking Factors
-Neutron population
What is Ex-core Neutron Monitoring(SE) used for ?
Monitor Neutron flux from detectors mounted outside vessel
What is Reactor Vessel Level Monitoring System(RVLMS) ?
-Provide indication of vessel level online & during accident conditions
-Manually augmented from Safety Injection to support indication
What does Chemical and Volume Control system do to Reactor Coolant System ?
-Provides charging and letdown to maintain PZR level
-Maintained proper chemistry
-Maintains Boron concentration during normal operation
-Increases boron when additional shutdown margin is required
-Provides backup auxiliary spray to PZR when normal path unavailable
-Provides constant purification of reactor coolant
-Provide RCP seal injection
What does chemical and volume control system collect discharge from the RCS?
-Coolant from drainage during maintenance
-Normal RCP seal bleed-off
-Discharge from primary safety valves
-Identified leakages- Valve packing or Pump seals
What does Nuclear Cooling water cool from Reactor Coolant system ?
-RCP Motor Air Cooler
-RCP motor lube oil cooler
-RCP thrust bearing lube oil cooler
-RCP seal coolers
-Acts as immediate barrier between RCS & plant cooling water system
What does Safety Injection System do ?
-Provide emergency core cooling& emergency Boron injection during design basis events
-Capabilities ensures reactor shutdown
-Provides both long term & short term cooling
What is Shutdown Cooling System used for ?
-Provides cooling for reactor when SG isn’t possible
What two systems work together following a Loss Of Coolant Accident?
Shutdown Cooling system and Safety Injection provide long term cooling during a LOCA
What does the 13.8KV NA system do for the Reactor Coolant system ?
Provides power to all 4 RCP pumps from NAN-S01& NAN-S02
What components does Instrument Air(IA)provide control air to, for the Reactor Coolant system ?
-Pressurizer Spray Valves
-Control Bleedoff Containment Isolation Valves
-Bleedoff isolation to the Reactor Drain Tank
What does Main Steam and Feedwater affect Reactor Coolant system ?
They provide heat removal from RCS
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What is the main purpose for the Reactor Vessel ?
-Contain & support core and vessel internals
-Contain & direct flow of coolant through core
- Provide pressure boundary to prevent fission product release
What’re the Reactor Vessel Internals ?
-Core Support Barrel
- Fuel assemblies and CEA
-Absorb CEA dynamic load and transmits loads to rector vessel
-Lower Support structure directs reactor coolant to core
-Instrument nozzles guide in-core instrumentation
-Upper guide structure aligns and guides CEA extensions
How many flow nozzles going into the Reactor Vessel ?
FOUR inlet nozzles going in & around core barrel
What does the Core bypass flow path do for the Reactor Coolant system ?
•Directs some of the Reactor Coolant entering the Reactor Vessel up into the Upper Guide Structure and Reactor Vessel Head to prevent stagnation of water in
areas of very low flow
•maintaining the temperature of the Reactor Coolant there below saturation temperature.
What is the cladding of a fuel rod made up of ?
Zirconium Alloy Tubes
What is the fuel used in the fuel rod ?
UO2 cylindrical pellets
Why’re the fuel rods pressurized with helium ?
- prevent cladding deformation
-Improve thermal conductivity of Pellet-To-Clad gap
What’re major components that comprise a Fuel Assembly ?
• 236 fuel Rods tubes
•16”x16” Fuel Assembly.
• Each Fuel Assembly contains 5 Guide Tubes.
• The four outer guide the CEA’s
• The 5th center one guide the incore instrumentation
How many total CEAs are in the Reactor Core ?
There are a total of 89CEAs
What’re the two types of CEA’s?
• 4 finger CEA (affect a single fuel assembly)
•12 finger CEAS (affect 5 fuel assemblies)
How do twelve-finger CEA work ?
They engage in a central fuel assembly and FOUR surrounding fuel assemblies (affects total of 5 fuel assemblies)
How do four-finger CEA work ?
They engage into a single fuel assembly
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What’re the groups CEAs are arranged in ?
-5 regulating groups
-2part strength rod groups
-2 shutdown groups
What’re twelve-finger CEAs exclusively used in?
Exclusively in shutdown banks A and B & provide shutdown margin
What CEAS does regulating groups 1,2,&3 use ?
They use BOTH twelve-finger & four-fingered CEAs
What CEAs do regulating groups 4&5 use ?
ONLY four-fingered CEAs
What CEAS does regulating 5 use ?
Contains only 1 subgroup of 4 CEAs
What does the PZR do for the Reactor Coolant system ?
-Maintains RCS in subcooled condition
-Minimizes pressure changes during load transients
-Ensures primary system integrity by preventing over pressurization
What is the surge line connect to ?
Connects bottom of PZR to the Coolant Loop 1 Hot leg
What’re the function of the PZR surge line ?
-Flow path for coolant surging to or from PZR
-Transmitting pressure in the PZR to the entire RCS
What’re the PZR heaters used for ?
Used to raise pressure inside PZR
How’re the PZR Heaters controlled ?
-Automatically by PZR pressure control system
-Manually by Reactor Operator
-Manually by AO directly at the breaker during loss of control power
What’re the two banks of class backup PZR heaters powered by ? What’re all other PZR heaters powered by ?
Class backups are powered from (PG):
-One bank powered from PGA
-Other bank powered from PGB
ALL OTHER PZR heaters are powered by Non-Class (NG)
What is the function of the PZR Safety Valves used for ?
•Limits RCS pressure less than RCS safety limit pressure of 2750psia
•Lift @ 2475psia
•Discharge to RDT
Where do the PZR safety valves discharge too ?
They discharge to Reactor Drain Tank where steam is released under water or be condensed and cooled
What happens if steam discharge from PZR Safety Valves exceeds capacity of RTD ?
RTD rupture disc will relieve to containment
When SDC is in service, what is used at over-pressure protection ?
It is provided by Low Temperature Over Pressure(LTOP) valves to mitigate peak pressure event while in shutdown and cooled
What is the purpose for Main Spray and Aux. Spray for the PZR ?
Used to reduce pressure by condensing steam in vapor space
When using Main Spray how does it operate ? When will Main Spray AUTO start?
-Sprays subcooled water into PZR from the Cold Leg of the reactor
-Valves start to open at 2275psia and are FULLY open at 2300psia
During normal operations when RCPs are running, what is flow controlled by going to Main Spray ?
They’re controlled by Diaphragm Valves:
RC-PV-100E
RC-PV-100F
What does Auxiliary Spray receive its water from?
Uses water provided by Charging Pumps
Why is Auxiliary spray more effective than Main Spray ?
Charging water is 110 degrees Fahrenheit Colder than the Cold Leg
Why doesn’t Main Spray work when RCPs aren’t running ?
DP across the reactor isn’t sufficient to maintain spray flow
What is the bypass flow used for on the two normal spray valves for the PZR ?
-Minimizes thermal shock to piping and spray nozzle when spray valve opens
-Limits Thermal Stratification
-Help circulate the PZR water in coolant loop to maintain chemistry & temperature in PZR
Why should you treat PZR spray valves gently ?
They’re metering valves, NOT isolation valves
What seals the reactor vessel and closure head ?
Two Self energized O-rings, that improves seal as RCS pressure raises
What’re the O-rings made out of ?
They’re silver plated because silver is malleable which allows O-ring to form tight seal
Why is there 2 Orings to seal the reactor vessel to the closure head ?
-There is two for redundancy
-Each O-ring has 100% capacity
-Inner O-ring Passive unless outer Oring has problems
What is the Reactor vessel head seal drain valve used for?
Used when O-rings detect high enough pressure to have some leakage between O-rings, this drain valve will drain that leakage out of O-rings
What’re SG components that interface with RCS ?
-Primary chamber
-Tube sheet & U-tubes
What constitutes a SG tube rupture ?
Loss of RCS barrier where CVCS CANNOT maintain PZR level
What is considered RCS system leakage ?
A RCS system leakage is when SG has a leak, but Chemistry & Volume Control System(CVCS) is able to be maintain PZR level
What is the Tech Spec limit for allowable RCS leakage ?
150gallons per day for a single SG
What’re RCP functions ?
What’re the functions of the RCPs ?
-Pump casing forms RCS Coolant Pressure Boundary
-Provides head for adequate coolant flow through RCS at normal operation
-Adds heat to primary system for heat ups
-Provides motive force for PZR Main Sprays
What does Main Oil for the RCPs lubricate ?
Provides lubrication for journal bearings and thrust bearings while pump is running
What is the accumulator used for in the Lift Oil system ?
Acts as a surge chamber that shock absorbs
What does Lift Oil do ?
It provides forces lubrication to thrust pads of thrust bearings, during pump is starting or shutting down
When should you start Oil Lift pump when starting an RCP ?
Oil Lift Pump should be started 7 minutes before RCP is started
Is oil lift pump normally running while the RCP is running ?
No it’s normally not running
When will Oil Lift Pump Deenergize after RCP starts ?
De energized after a specified time delay of TWO minutes
What must you do to satisfy the “start permissive” for RCP ?
If Lift Pump is not already running you just manually start pump, THEN start RCP
How would you need to start the Oil Lift Pump AFTER the RCP has been running for 2 minutes already ?
Oil Lift Pump hand switch must be held in start position to work. Then when released it will spring back to auto position and stop the pump
What must you do to Lift Oil Pump Switch before stopping the RCP ?
Must place switch in AUTO, so it auto starts when RCP is shutting down
What happens if Lift Oil Pump doesn’t AUTO-start when shutting down RCP ?
You must manually switch Oil Lift Pump to START
What is the purpose for the RCP shaft seal assembly ?
-Acts as pressure boundary between RCS & containment
-Minimizes pump leakage
Where is External Seal Injection Water get its water from ?
From charging system
Where is the majority of the seal flow routed to ?
Routed down by Auxiliary impeller through journal bearing and into Lower Journal Bearing Cavity
What does Seal Water do for RCP journal bearing ?
Provides cooling and lubrication
Why is each cooler designed to provide 100% pressure drop?
In event of a failure of the seal below it and is capable of operating at full system pressure
What percentage is pressure drop across seal cooler #1?
42%
What percentage is pressure drop across seal cooler #2?
42%
What percentage is pressure drop across seal cooler #3?
16%
What is the flow rate through all 3 seals ?
2.6GPM
Where does seal #3 flow too? Where does leakage past the Vapor Seal go ?
-Flows through flow restrict and into Volume Control Tank
-Leakage goes into Reactor Drain Tank
What is the seal bleed off isolation valves interlocked with ?
-Seal Bleed Off is interlocked with RCP
-Isolation valves will not close if associated RCP is running
When will abnormal operation be entered with RCPs?
-Seal Injection Flow is to low
-Seal temperatures are to high
-Seal leakage is indicated
What’re prerequisites for flushing Cyclone filter ?
1.)RCP shutdown
2.)Plant in Mode 5
3.)RCS press. less than 300psia
4.)RCS temp. less than 200
5.)Seal injection in service
6.) RDT toward low end for more room for water being flushed
7.)RCP shaft seal package installed
8.)RCP shaft seal is NOT scheduled to be replaced
What is supposed to be monitored when doing cyclone filter flush ?
-Reactor Drain Tank
-Reactor Drain Tank Temperature
-Reactor Drain Tank Pressure
What is RCP motor flywheel help with ?
-helps increase rotating inertia
-Increase pump coast down
-Reduces rate-of-decay of coolant flow when power is lost to RCP
-coast down helps ensure adequate heat removal and transition to Natural Circ.
How does RCP motor flywheel help coast down ?
Helps ensure adequate heat removal from and helps transition Natural Circulation
What is the purpose of a RCP anti-reverse rotation device ? When does it come into play ?
-Mounted on top of rotor to prevent reverse rotation of motor
-Function is to stop pump when it reaches zero speed as it decelerates from running speed while other pumps continue operate
What conditions will automatically trip the RCP ?
-Undervolatge
-Coast -down(LOOP)
-Over-Current
-Speed less than 600 RPM after a few seconds
What’re the positions of the switch for the RCP ?
Controlled by 3 position switch STOP/NEUTRAL/START
When RCP is placed in START what conditions must be met to start ?
-No motor fault trip exits
-Oil Lift Flow sufficient
-Nuclear cooling water flow is efficient
-RCP seal bleed-off valve fully open
What is the Tech Spec for RCS pressure ? (Modes 1-5)
RCS pressure is limited to 2750psia
What is the Reactor Core Tech Spec ?
-DNBR
-Peak Fuel Centerline Temperature
What is Reactor Core LCO?
Power Distribution Limits
What is LCO for Reactor Coolant ?
-Temperature,Pressure, & Flow (To prevent DNBR)
-Minimum temperature for criticality
What is LCO for RCS piping ?
-Pressure & temperature limits( prevents pipe or vessel failure)
What modes do RCS loops must be operable?
MODES 1-4
What modes should RCS loops be filled when SDC is required?
MODE 5
What is LCO for pressurizer ?
-Must be operable in modes 1-3
Level:>27% & <56%
2 groups of heaters
How many Pressurizer Relief Valves must be available in modes 1-3 ?
Four PZR relief valves must be available
How many PZR relief valves must be available in mode 4 ?
One must be available in Mode 4 when temp is above LTOP limit
How many PZR Vent Paths must be operable in Modes 1-3?
Four vent paths must be operable
What’re RCS Operational Leakage limited to what ?
-NO pressure boundary leakage
-1 gpm unidentified leakage
-10 gpm identified leakage
-150 gpm leakage through any one SG
What kind of leak detection is needed in modes 1-4?
-One Containment sump level Monitor
- One containment atmosphere radioactivity monitor
