Charging & Letdown(CH) Flashcards
What does Chemical Volume & control system do for the RCS ?
1.)Maintain RCS chemistry for corrosion control
2.)Control RCS PH
3.)Remove corrosion & fission products from RCS
4.)Remove dissolved or entrained gases from RCS
What does Chemical Volume & Control System do for the RCS Inventory Control ?
1.)Maintain RCS water inventory
2.)Replaces RCS losses to containment due to leaks in small lines
3.)Provides makeup to RCS for safe shutdown during Natural Circ.
What does Chemical Volume & Control system do for the RCS Reactivity Control ?
1.) Maintains RCS boron concentration to compensate for reactivity changes
2.)Compensate for changes in RCS boron throughout core life to control RCS temp
3.)Borate RCS for safe shutdown during Natural Circ. Using only one charging pump
4.) Inadvertent deborated can be detected& terminated before loss of shutdown margin
5.) RWT is sized to fill Refueling Pool & Transfer Canal support of refueling operations
What does Chemical Volume & Control System do for RCS Pressure Control ?
Provides Aux. spray for manual control of press. & PZR cooldown during:
-Final stages where RCS pressure is below that required for RCP operation
-Natural Circulation conditions
How does Chemical & Volume & Control System do for Emergency Core Cooling ?
-Letdown line can be isolated in event of SIAS & CSAS
-Passive isolation of charging line is provided by an inboard check valve
When will the Letdown Line penetrating containment automatically isolate ?
-SIAS
-CIAS
When will Control Bleedoff Flow from RCP seals penetration line isolate on what kind of signal ?
CSAS
What signal will isolate Reactor Drain Tank penetration line?
CIAS
What does Chemical Volume & control system do for Reactor Coolant Leakage Detection ?
-Process indication within CVCS provides means to identify & quantify normal RCS leakage
-Instrumentation provided to identify occurrence of letdown line break outside containment
How does CVCS support Steam Generators ?
-Alternate makeup from Reactor Makeup Water Tank to SGs via Aux. Feed water system
How does CVCS support Spent Fuel Pool ?
-Primary method of borated water from RWT to Spent Fuel Pool
How does CVCS support RCS inventory during Station Blackout ?
During station blackout Charging pumps could be used as alternate method of controlling RCS inventory when leakage from RCP seals is <83gpm
Why must letdown temperature & pressure of flow be reduced when going to CVCS ?
Must be reduced to to meet CVCS component design & operational requirements
What does Letdown Flow first run through a Delay Coil ?
To allow decay of N-16 activity
What two flow paths are passing through Regenerative Heat Exchanger ?
-Letdown is flowing through Tube Side
-Charging for Reactor Coolant Makeup is flowing through shell side
What is the Regenerative Heat Exchanger used for ?
-Charging will get cooled by LetDown
-Letdown will Heat up Charging
How’re the Letdown Control Valves positioned ?
Positioned in response to signals from PZR level controller
What other subsystem taps into the letdown flow path ?
Shutdown Cooling Purification which permits purification during shutdown conditions
What cooling water is sent through the Letdown Heat Exchanger shell side to cool Letdown?
Nuclear cooling water
What’re the Back Pressure Control Valves located after letdown heat exchangers used for ?
They’re used to prevent flashing inside the Letdown Heat Exchanger by maintaining pressure inside heat exchanger
Why is Letdown flow passed through 1of2 purification filters ?
-Removes insoluble impurities to reduce crud buildup on equipment
Where is a portion of letdown flow routed to ? What will automatically bypass Letdown flow to ?
-Routed through abandoned Boron meter & Radiation Detector
-High Temperature will bypass boronmeter & Radiation Detector
What kind of Ion Exchangers are used in Letdown system ?
-2of3 are Purification Ion Exchangers
-Third Ion Exchanger is a Deborating Ion Exchanger
Which Ion Exchangers are continuously in service ? What does this Ion Exchanger remove ?
1OF 2 Ion Exchangers are in service continuously removing ionic materials & particulates
How often is the Second Purification Ion Exchanger used? What is it supposed to do ?
It is used periodically & is used to remove lithium from Reactor Coolant as necessary for PH control
What happens once Ion Exchangers lithium capacity becomes exhausted after one core cycle ?
That ion exchanger is then used for continuous purification the following core cycle
When is deborating ion exchanger used & why ?
It is used near the end of core life because it minimizes liquid waste accumulation
What condition will automatically bypass Ion Exchangers ?
They’re bypassed on high temperature to prevent resin from being damaged
What does the outlet flow from Ion Exchangers send flow through ?
Common discharge line strainer to collect any resin particles
What is the gas space filled with in the Control Volume Tank ? What is used for ?
Hydrogen gas is in the CVT & it is used for oxygen scavenging for RCS chemistry
What does the VCT do for the RCS ?
It acts as a surge tank for RCS to accommodate mismatches between: -Actual & programmed PZR level
-Collects RCP bleed off
-Provides NPSH for Charging pumps
What happens when High Water level is reached inside the VCT ?
Excess water is diverted to preholdup ion exchanger which then goes to CVCS Hold up Tank
What is normally the status of the Charging Pumps during operation ?
-1st pump is ALWAYS in service
-2nd pump is normally in service
-3rd pump is in standby
How does Charging flow get heated up before entering RCS ?
Charging Flow gets heated by passing through Regenerative Heat Exchanger at the SAME time at Letdown flow coming from RCS
What does the charging system do for the PZR ?
Charging system provides Aux. Spray to the PZR when Main Spray isn’t available
How is the Letdown & Charging system normally operated
Normally operates by automatic control
How much bigger in diameter are the Delay Coil pipes compared to Letdown Pipe? Why’re the Delay Coil pipes bigger in diameter ?
-Letdown flow pipe is 2inches while Delay Coil pipe is 16 inches
-A bigger diameter will slow water down and allow for more time to allow decay of N-16 gammas within Bioshield
How much delay time does the Delay CoilS provide ?
They provide 95second delay through two 11.5’ section of pipe
What is Letdown Regenerative Heat Exchanger Isolation Valve UV-515/UV-516 used for ?
-Remain open to allow letdown flow
-Auto closes on SIAS or High Regen. Heat Exchanger outlet at 413F
-A CIAS only closes UV-516
-Manually closed to isolate letdown during a letdown line break
What is Regenerative Heat Exchanger Outlet Isolation Valve UV-523 used for ?
-Remain open to provide letdown flow
-Auto closes on CIAS
Or
-High Letdown Heat Exchanger OUTLET temp of 135F
What positions do the RHX isolation valves fail in ?
They failed closed on loss of instrument air or power
What does the “Remote-Local/Local” disconnect on the Remote Shutdown Panel(RSP), do for UV-515 Regen. Heat Exchanger?
REMOTE-LOCAL:
-Will be able to operate valve from control room or RSP & all auto features available
LOCAL:
-Only allows operation from Remote Shutdown Panel, ALL indication & control isolated from main control room
-The ONLY auto feature is HI RHX temp. UV-515 auto close
Where is the UV-516 letdown to Regen. Heat Exchanger controlled from ?
-Valve is controlled from Control room or Remote Shutdown Panel
Where is the UV-523 Regen. Heat Exchanger Outlet Isolation Valves controlled from?
Controlled from Control Room
What is the Regenerative Heat Exchanger used for ?
-Transfers heat from letdown flow into charging flow to prevent thermal shock on charging nozzles
-Letdown water gets cooled by charging to protect letdown system
-Conserves plant heat(EFFICIENT)
What flow is on the shell side & what flow is on the tube side ?
Shell side-Charging Flow
Tube side-Letdown Flow
What temperature is the Outlet Regen. Heat Exchanger supposed to be maintained at ?
Supposed to maintain outlet temp. of <413F
What’re the Letdown Control Valves used for ?
-They adjust letdown flow based on PZR Level Control System
-Reduces pressure for letdown components downstream
What position will Letdown Control Valves fail to ?
They will fail closed on loss of Instrument Air & NK power
When PZR Level Control System is in automatic what is letdown flow limited too ? Why ?
-Limited between 30-135gpm
-Limited to 135gpm to prevent channeling in Ion Exchangers
If RCS pressure is >1000psia, how many letdown valves are in service ?
If RCS pressure is <1050psia, how many letdown valves are in service ?
> 1000psia ONLY 1 letdown valve in service
<1050psia BOTH letdown valves are in service
What is the Letdown bypass valve used for ?
Used to warm up Letdown Heat Exchanger when Letdown is secured at power
What happens if letdown flow is isolated more than 22minutes ?
-Letdown control bypass valve must be opened for at least 4 minutes prior to initiates letdown flow
-Minimizes thermal transients
What cooling water is used Letdown Heat Exchanger ? How much is letdown cooled ?
-Nuclear cooling water cools let down heat exchanger
-Cools it to 110 degrees to prevent damage to Ion Exchangers resin(<140)
What’re the Letdown Back Pressure Control Valves used for?
-Control pressure & ensures sub cooled conditions in letdown heat exchanger
What pressure do the Back pressure Control Valves maintain Downstream & upstream pressure at ?
Upstream-375psig to prevent flashing in letdown heat exchanger
Downstream-Maintained between 40-95psig downstream to prevent damage to components
When will the BackPressure Control Valves automatically isolate ? What position do they fail in ?
-Isolate on HI-HI temp of 148F at outlet of Letdown Heat Exchanger
-They fail close on loss of Instrument Air
What is the Regenerative Heat Exchanger to Letdown Heat Exchanger pressure relief valve Set Point ?
600psig
What is the Purification Filter Inlet relief valve Set Point ?
200psig
Where do the pressure relief valves discharge too ?
Bothe discharge to Equipment Drain Tank
What do the Purification Filters remove ? What micron are they ?
Removes 98% unsoluble particles greater than 2micron from letdown flow
What kind of filters are used for Purification Filters?
Removable cartridge type
What conditions must the purification filters be changed ?
-DP greater than 25psid with max letdown flow of 72gpm (Alarm activates in control room)
-Rad levels 5 R/hr
During normal operations what condition will the Purification filters need to be changed out first by ? What about outage operations ?
-Rad level limit will be reached before DP limit during normal operation
-During outage DP limit will be reach first before Rad Level Limit
What does the RCS Letdown Radiation Monitor do for the system ?
Indirectly monitors Fuel Clad Status
What does Radiation Monitor measure to monitor fuel cladding status ? How is the output displayed?
-Measures gross gamma radiation of the Letdown passing by, if there is a failure gammas will increase
-Output is displayed on RMS computer for current reading,trending,& monitor status
What does the Radiation Monitor Flow Control Valves do for the Radiation Monitor ?
-Throttles to create DP across itself forcing flow through RPM
-Monitors flow & controls to create a flow of 8gpm
When will the Rad Monitor/Boronmeter inlet bypass valve bypass radiation monitor ?
Will divert slip stream flow on High Letdown Temperature
What position m does the Flow Control Valve fail to ?
Will fail open on loss of air or power to flow controller
What is the Ion Exchangers Inlet/Bypass valve used for ?
-Directs letdown flow through Ion Exchangers during normal operation
-Bypasses Ion Exchangers during High outlets temp of Letdown HEX
When temp will the Ion Exchangers Inlet/Bypass valve, bypass the Ion Exchangers ? What happens on a loss of air or power to this valve ?
-Outlet temp of 135F will bypass Ion Exchangers
-On loss of Air & Power it fails to divert flow around Ion Exchangers
What’re the 3 Ion Exchangers labeled as ?
-Purification Ion Exchanger
-Purification Ion Exchanger
-Deborating Ion Exchanger
All Ion Exchangers are interchangeable, but what’re they used for based on the life of the resin ?
Purification-Removes normal levels of RCS impurities and radionuclides from letdown
Delithiation- Removes lithium to control RCS PH
Deborating- Reduces RCS boron concentration at end of cycle when dilution is inefficient
How much resin does each Ion Exchanger hold ?
Holds 35 cubic feet of resin
When is the Purification Ion Exchanger & how is it used ? (Mixed bed 1-1 Cation to Anion)
-Continuously in service
-Placed in standby during delithiation
-Conditioned with boron prior to used to prevent removal from boron so reactivity isn’t affected
-Loaded with lithium to remove Cation impurity removal without affecting Lithium levels in RCS
When is the Delithiating Ion Exchanger placed in service? What happens once Lithium Capacity becomes exhausted? (Mixed Bed1-1 Cation to Anion)
-Normally in standby and only placed in service when lithium levels in RCS are high
-Placed in service on night shift for 15mins or 7hours
-ONCE Exhausted it is used as a purification filter for next core cycle
When is the Deborating Ion Exchanger placed in service ? How is normally maintained ?
-Anion Resin Bed
-Normally used at end of Core Life to remove boron below 30ppm
-Normally maintained inlet & outlet valves secured with equip. Status Tag Hung on hand-wheel to prevent operation
What is the common D/P indicator installed across the three Ion Exchangers used for ? What DP does it typically read out to ?
-Used to it Ion Exchanger is clogged
-Used by AOs to verify proper operation of Ion Exchanger isolation valves
-Typically reads 4-6psid
What is done to place Delithiation Ion Exchanger in service WITHOUT isolating Letdown flow ?
1.)Place delithating in parallel with purification Ion Exchanger
2.)Overall D/P will drop to 2-4psid
3.)Then Purification Ion Exchanger will be placed in standby
4.) D/P will increase
What is the local flow indicator used as a confirming indication for ? What flow does the flow indicator usually indicate ?
-Used as confirming indication during a delithiation
-typically reads 72gpm
What is the Letdown Strainer at the discharge of the Ion Exchanger used for ?
Designed to catch resin bead fines and prevents contaminating system from very small radioactive particles
What is the Volume Control Tank used for?
-Acts as a surge tank for charging/letdown mismatches
-Required NPSH for charging pumps
-Hydrogen to RCS for oxygen scavenging
-Collects bleed off from RCP seals
-Provides make-up to RCS
How many gallons does VCT hold ?
4900 gallon capacity
How does increase pressure in VCT affect RCP Seal Bleedoff ?
Increase in VCT pressure will increase back pressure, for Bleedoff flow which decreases Bleedoff flow rate
What is the VCT pressure normally maintained at ?
Normally between 20 & 250psig
When is Nitrogen added to CVT ?
Nitrogen is added during shutdown modes for Oxygen exclusion
What happens when VCT reaches a high level of 60% lvl? What happens when VCT goes back down to 58%?
-VCT inlet valve will divert letdown flow to Pre-Holdup Ion Exchanger during VCT high level
-Resets level controller, which will divert flow back to the VCT
What happens to VCT when level reaches 5% ?
-VCT outlet valve will close to prevent air binding the charging pump
What happens when discharge valve UV-501 of VCT closes on low low level?
-BAMPs discharge valve UV-514 will open, and a BAMP will start and begin voracious
What happens if UV-514 loses power and VCT level 5%or lower ?
Gravity makeup valve UV-536 will automatically open
If CVT discharge valve(UV-516) is closed, along with Gravity Makeup Valve(UV-536) closed without a VCT low low level what will happen ?
VCT discharge valve(UV-501) will automatically reopen when valve finishes stroking in close direction
When will UV-501 automatically reopen ?
When VCT level recovers to 15% then VCT discharge valve will auto open
What is the LC-226 do for the VCT ?
Sends signals to the Makeup Control Circuitry for auto makeup to VCT
Where does VCT Makeup Control Circuitry send its signals to ?
Makeup Flow Control Valves
-210X-Reactor Makeup Water to VCT
-210Y-Boric Acid Makeup VCT
Makeup Flow Path Valve
-Makeup Inlet to VCT
Although there is a Level Controller to maintain VCT level, what is normally used to control level ?
-VCT level is controlled manually between 40%-60% to maintain positive control of potential reactivity manipulation instead of letting plant control evolutions
What is Blended Makeup to the VCT ?
-Addition of non-borated water from Reactor Makeup Water Tank & Borated Water from Refueling Water Tank to minimize reactivity change
What is the reason for Dilution makeup for the VCT ?
-Addition of Non-Borated water from Reactor Makeup Water Tank to CVT will lower boron of charging water, which will reduce boron in RCS, which will add positive reactivity
Where can the Charging Pumps draw their suction from ?
-Volume Control Tank
-Refueling Water Tank
-Spent Fuel Pool
Where are the charging pumps providing flow to ?
-RCS makeup
-Aux. Spray
-RCS boration
-RCP Seal Injection
What is the designed discharge pressure and gallons per minute for the Charging Pumps ?
Discharges 44gpm at a discharge pressure of 2375psig
What’re statuses of the Charging Pumps during normal operation ?
ALWAYS running-PZR control system CANNOT stop pump
Normally running- High PZR level signal automatically STOP pump
Standby - Low level PZR signal will auto START pump
What’re the Charging Pumps powered from ?
‘A’ pump is powered by class PGA
‘B’ pump is powered by class PGB
‘E’ pump can be powered from either train
How can the ‘E’ charging pump be powered from both trains of PGA OR PGB ?
-Transfer ‘E’ charging pump breaker from one train to another, then closing disconnect to that selected power supply
What does the seal water system do for the Charging Pumps?
-Provides packing lubrication & to control leakage of reactor coolant from charging pump seals
When will Seal Water pump start ?
Will start when associated charging pump is started
When is the Seal Lube Pump started ?
-Seal Lube Pump is ran for 10 minutes BEFORE charging pump is started
-Verifies proper seal lube pressure to prolong life of charging pump packing
How long can Charging Pump run without Seal Lube Pump ?
-It is allowed to run without Seal Lube Pump for 50hours ONLY during emergency conditions
What is the automatic makeup to the Seal Water Expansion Tank?
Automatic makeup from RMW header
What is the suction stabilizer used for ?
Absorbs pressure surges in charging pump suction piping
What is the stabilizer capacity? What does stabilizer contains inside it ?
-Stabilizer capacity is 10 gallons
-Contains a nitrogen charged bladder & flow deflector
What is the pre charge pressure at ? What is the flow deflector used for ?
-Precharge pressure is at 19psig
-Flow deflector directs flow towards the bladder which absorbs the shock,which reduces vibration in pipe
What’re the pulsation dampeners used for ?
Dampens pulsations in the Charging Pump discharge piping
What does the Dampener contain ?
-Contains 1500psig Nitrogen charge bladder
-Spring Loaded Poppet
-Fixed flow diversion baffle
What does the diversion baffle do ?
Diverts some discharge flow through poppet and bladder interface to absorb pressure surges
What is the spring loaded poppet do ?
Compensates for small pressure changes
When is bladder pressure adjusted ? What is the range ?
-Bladder pressure is adjusted during startups & shutdowns to prevent system perturbations
-Range is 30-70% CH header pressure with a target of 60%
What’re the additional requirements for charging pump during pre/post operational checks ?
Pre-start checks:
-Seal Lubricating Pump running at required pressure
-Oil pressure
Post start checks :
-Room ventilation
-Oil pressure based on temp
What is the commitment to NRC regarding the isolation valve at the discharge of the charging pump ?
Commitment is to lock open power supply to prevent isolation of PZR Aux Spray Flow path
What does the Charging Line Back pressure Control Valve do ?
-Ensures proper distribution of charging flow to RCP seals & Aux.Spray
-Maintains backpressure for Aux spray
-Maintains backpressure for RCP Seal Injection
-Maintains backpressure to minimize charging pump pulsations
-Fails closed on loss of power or instrument air
What does the Charging Line Isolation Valve do ?
-opens to provide normal charging flow through RCS loop 2A
-If back pressure control valve fails open, this valve will close to maintain Aux. Spray through a bypass check valve
What is the Bypass Line Check Valve do ?
Opens to let charging flow pass upon closure of valves 239 or 240
What’re the PZR Aux. Spray Valves for?
-Open to provide Aux. Spray Flow to PZR
-Close to terminate spray flow and isolate RCS from charging system
-Provides PZR pressure control when normal pressure control isn’t available
Where do PZR Aux. Spray Valves receive there power from? What position do they fail in ?
-They powered from PKB-D22 & PKA-D21
-Valve fails closed on loss of power
What is Tech Spec for How many charging pumps need to be functional while in shutdown?
-At least one charging pump, one HPSI pump, or one LPSI in Boron Injection flow path
-Shall be function and capable of being powered from an operable emergency power source
-In modes 5&6
During operations how many charging pumps should be functional?
At least two charging pump should be functional in modes 1,2,3,4
What is the Tech Spec for how many Aux. Spray Valves should be functional ?
BOTH aux. spray valves should be functional in mode 1,2,3,4
