• Maintain RCP Seal Injection
• Control RCS Chemistry (B-, N2, H2) and RCS Activity
• Process Rx coolant effluent to recover/reuse B & make up water
• Fill, drain and hydro test the RCS
• Cooldown the PZR during shutdown (Alternate Spray)
• Performs Saftey Injection Function
• Emergency Boration
• Maintain RCS water inventory thru auto control of Pzr water level

CVCS Design Basis:

Safety Related

Safety Related

• High Head safety injection to cold legs on LOCA
• Containment Isolation Valves
• Emergency Boration
• Two Charging Paths (Regen HX and RCP Seal Injection)
• One safety grade LTDN (Letdown) Path from RX head vent
• 2 Non Safety Related LTDN Paths (Normal and Excess)

CVCS Design Basis:

Non-Safety Related

Non-Safety Related

• Maintain PZR Level
• RCP Seal Injection
• Reduce concentration of fission and corrosion products thru filtration and ion exchange
• Adjust RCS Boron
• Cooldown PZR during plant cooldown
• Enough B- to shutdown the Rx from any operating condition to cold shut down
• Maintain concentration of dissolved gases in RCS within the proper range
• Reclaim Boron
• Fill and Hydrotest RCS

Regen HX:

Purpose and Function

Designed to transer heat from LTDN flow to charging flow to decrease thermal shock to RCS charging inlet nozzles and decrease the heat load on LTDN HX.

Cools LTDN to 275 F and preheats Charging to 495 F.

Eliminates reactivity effects of adding cold water to the RCS, 3 shell and tube HX, shell side 2485 psig, charging flow and tube side 2735

LTDN takes RCS from 24 intermediate leg cools and transports RCS to Demin Beds for filtration and recirc thru the Charging Portion of the system.

2CV2 and 2CV277

LTDN Isolation Valves

Isolate LTDN on Low PZR level, fail closed AOVs

Interlocks:

• Both must be open for CV 3/4/5 to open, prevents water hammer.
• If either CV2 or CV277 close then CV 3/4/5 will close
• Isolate on Lo-Lo Pzr Level (17%) when in automatic
• CV2 (control channel) CV277 (Alarm Channel) can be blocked with key interlock, will not isolate if valves are in manual.

CV3/4/5 LTDN Orafice Isolation Valves

Purpose and Interlocks

Used to isolate containment in accident conditions and place orafice in and out of service. AOVs, fail closed. Limit LTDN flow to < 120gpm.Individual flow rates CV3=45 gpm; CV4=75 gpm, CV5=75 gpm.

Interlocks:

• Close on Phase A isolation
• Close on loss of all Charging Pps
• Close when CV2/CV277 close
• Close on Lo-Lo Pzr level (17%)

_{CV 6 LTDN Relief Valve}

_{Purpose and Setpoint}

Relief valve for LDTN system, near CV3/4/5.

Relieves to PRT, setpoint is 600 psig; capacity is greater than max LTDN flow thru all orafices (500 gpm water or 43,000 Lbm/hr saturated steam)

CV8 RHR Purification Flow Control Valve and

RHR Booster Pump

Purpose

CV8- controls LTDN during RHR operation and allows for clean up thru demins upto 100 gpm, controls the flow rate of RHR.

RHR LTDN Booster Pp- increase flow (~ 180 gpm) to improve crud burst efficiency.  Decreases outage time b/c less waiting for doses to come down in the plant. Located upstream of CV8, can only be used in Modes 5 and 6.

CC-71 LTDN Temperature Control Valve

Purpose and Interlocks

Safety Related AOV, Fails closed 

"Auto" operation, CCW flow maintains 100 F CVCS LTDN (temperature protects Demin Beds from resin degradation)

"Manual" MCR adjust temperature up and down.

Interlock-

CV7 closure will close CC71 because a limit switch on CV7 de-energizes the CC71 solenoid.

This interlock is in place to address CCW hydraulic concerns during a LOCA; to prevent CCW pp runout for a single CCW train operation with single CCW PP running, prevents diversion of cooling water flow from RHR HX and ECCS Pp seals.

Control Pressure downstream of LTDN heat exchanger to prevent flashing of steam downstream of letdown orafice. Also used for RCS pressure control when solid. AOV fails open.

Operated in Auto or Manual, will modulate to maintain pressure setpoint of 300 psig.

CV-35 Diversion Valve

3-way AOV fails to VCT, except on loss of vital instrument bus which causes it to fail to the CVCS-HUT. Diverts LTDN to CVCS-HUT when VCT level is high (LT-114), when in auto.

Modulates open at > 77%, fully open at 87%.

LT 112 will trip open CV35 at 87% (This is a backup signal)

Fails High:

Loss of auto makeup 

CV35 goes to full divert

No swap signal @ 3.57%

VCT High Level Bezel Alarm

Bezel indicator reads high

Fails Low: 

VCT Low Level Alarm

No CV35 trip (full divert)

Bezel indicator reads low

Continuous Auto Makeup

Fails High-

CV35 goes to full divert

No swap signal at 3.57%

VCT level lo-lo alarm disabled

Fails Low-

VCT level lo-lo alarm

CV35 can't modulate

VCT Purpose and

Indications/Setpoints

Functions: 

• Surge Capacity for RCS (2990 gallons)
• Degas RCS prior to SD (via CV243 to WG Header)
• Add H2 to RCS 
• Head Tank for Charging Pps
• Reservoir for RCP Seal Leakage

Indications and Set Points:

Hi Level- 87.2%

Lo Level w/o auto m/u- 14%

Lo Level w/auto m/u- 11%

Lo-Lo Level- 3.57%

Hi Pressure- 50 psig

Lo Pressure-10 psig

Hi temperature

Adds depleated zinc oxide to RCS which supports source term and dose reduction, and mitigates Primary Water Stress Corrosion Cracking. Maintain 5-10 ppb, with max of 30 ppb.

Potential Risks of Zinc Addition are clad corrosion, crud induced power shifts and axial offset anomoly

MOVs, Power Supplies (CV40, A train, 230V C West; CV41, B Train, 230VB West)

Interlocks-

CV40/41 with VCT Lo-Lo Level 3.57%- purpose of this interlock is to maintain suction head for Charging Pps. Occurs when VCT level is lo-lo, and swaps suction to RWST.

• Interlocked with SJ1/2 RWST to Charging Pp Suction isolations. On 2/2 Lo-Lo level in VCT, SJ1/2 will open. When either SJ1/2 are open then CV 40/41 will close, if in Auto. No transfer if in manual.

SI Interlocks- response to LOCA, SI will complete the swap correctly whether in Auto or Manual.

• In Auto: SJ1/2 told to open, all valves have operator lock out until SI reset, once SJ1/2 are open, then CV40/41 will close.
• In Manual- SJ1/2 told to open, all valves have operator lock out until SI reset, once SJ1/2 are open, then CV40/41 will close.

Charging Pumps:

Suction Supplies

• VCT (normal)
• RWST (back upand emergency via SJ1/2)
• 22 RHR Pp Discharge- 22SJ45 cold leg recirc following and SI.
• 21 RHR Pp discharge-21SJ45 and 21SJ113 or 22SJ113, used during cold leg recirc following SI

Flow Demand- Controlled by Master Flow Controller (MFC) (on CC2).

In Auto, MFC recieves input from LC 459 (PZR level) and outputs signal to PDP and CV55 to raise/lower flow to maintain PZR level.

Max Flow- 98 gpm at 2500 psig

Low Speed Stop-Min Flow of 47 gpm

at 2500 psig, ensures adequate seal injection to RCPs.

Interlocks:

• Pp motor tripped by SEC stripping in modes 2/3/4
• Pp Starting Circuit provides open permissive to letdown orafice isolation valves CV3/4/5
• All modes prevent start/stop until SEC Reset.

System Interfaces-

• Seal Water Tank- Lubricates Plungers
• Low Lube Oil Pressure (< 4psig)
• CCW (100 gpm) cools speed changer and lube oil coolers
• Power A 460V Vital Bus
• Relief Valve- CV-141 on Pp discharge line, setpoint 2735 psig, relieves 100 gpm to VCT

Functions: Provide High Head Safety Injection (via RWST and BIT) to all RCS cold Legs during LOCA. Also provide charging flow at rates greater than the PDP.

Capacity- 150 gpm at 2500 psig

System Interfaces:

• Power- 21- 4KV B VB, 22- 4KV C VB
• Aux Lube Oil Pp and cooler supplied by SW
• Constant Speed w/ flow control via modulating CV55
• Min Flow Recirc Valve (CV 139/140) maintain 60 gpm flow thru seal water HX to ensure Ch and SI pps don' overheat, opens 2000 psig, close 1500 psig

Interlocks:

• Start on SEC and operator Lock out until SEC reset
• Provide open permissive for CV3/4/5
• energize/open SW supply to gear/lube oil coolers
• Pp start/stop signals Aux Lube Oil Pp (start on PP start, off at >12 psig; starts on Pp stop, runs for 1 min, starts when Ch Pp operating and lube oil pressure is < 8 psig, runs until pressure is >12 psig (SEC blocks Aux Lube Oil in modes II/ III, 230V AC lock out.

Trips:

• Bus Diff
• Bus Overload
• SEC Load Shed
• Brkr Overload Ground

Modulates to maintain flow rate based on error between PZR actual level and programmed level.

Low Flow stop at 47 gpm to ensure adequate seal injection to RCPs. Fails FO at 3 psig and closed at 15 psig, normal position range is 3-11.3 psig; auto or manual operation.

Fed signals from 2CA2015, does not have a bumpless transfer when placed in normal/bypass, charging flow controller must be above minimum setpoint prior to manipulating.

Maintains back pressure in charging header to RCP seal flow.

Normally open, fails closed to ensure seal injection.

Seal Water Return Valves

CV 116/CV 284

CV 115

The CV 116 and CV 284 are Phase A containment  isolation valves. CV 284 is isolation on containment side. 

If seal return isolates, then relief valve CV 115 opens at 150 psig and relives to the PRT providing a flow path to the RCP seals.

Used in place of or to supplement LTDN. Max flow is 25 gpm.

Challenges with operation of Excess LTDN-

• No Clean Up of RCS, because this path does not flow thru Demins
• Boration and Dilution will take longer, limit power changes
• PZR level will slowly increase as Ch flow exceeds the capacity of the Excess LTDN
• Normally aligned to the VCT by can go to the PRT.

Make Up Control System

Purpose and Modes

Provide makeup water to the VCT. This system is compromised of the PWST and Pp and Boric Acid Tanks/Piping and Pp.

Performs:

• Auto make up- suction water from PWST and BAT/BAT Pp to match the B concentration of the RCS.  (more detail on next card)
• Boration- via the BAT and Pps (BAT Pp to fast, open CV185 to suction of Ch Pps, CV-172 Close to Obtain BA flow=setpoint, Auto stops when flow totalizer reaches Setpoint.
• Rapid Boration- via the BAT and Pps (used when SD Margin < TS limit, RX Trip with 2 Rods not fully inserted, Rods below Rod insertion Limit.
• Dilution- PWST via via open CV 181 VCT inlet/ open CV179 obtain PWST flow= setpoint, CV172 closes, will auto stop when flow totalizer reaches setpoint
• Alternate Dilution- PWST via open CV 181 VCT inlet/ open CV179 obtain PWST flow= setpoint, CV172 closes, will auto stop when flow totalizer reaches setpoint
• Alternate-Alternate Dilution- use Alt Dilute Flow path and administratively controls CV181. 

Make Up Control:

Auto Make Up, Setpoints and Operation

Auto Make Up:Operates on demand from VCT level (LT112), start 14%, dilution will auto stop when flow totalizer reaches setpoint (24%).

Make Up-Non-Auto:VCT Level Lo 14% and Make up mode not selected or make up in auto but not did not start on selected mode switch.

@14% VCT Lvl

1. Auto BAT Pp shifts to fast (75 gpm)
2. Auto PW Pp starts
3. CV 185 opens at suction of Ch Pps
4. CV 179 opens to obtain PW flow, set point 62 gpm
5. CV-172 closes to obtain Boron Flow, setpoint determined by current RCS concentration.

@ 24% VCT Lvl

1. CV 185 Closes
2. CV 179 Closes
3. Auto Primary Water Pp stops (Bezel Alarm)
4. Auto BAT Pp shifts to slow (37.5 gpm) (Bezel Alarm)
5. CV-172 Opens, increase light lit on Bezel

SEC Modes:

• Mode I: If in Auto Make Up- SEC trips Boric Acid Pp only and operator Lock Out until SEC reset. (Loss of Boric Acid causes Boric Acid Flow Deviation, closes CV181 and 185 after 2-60 sec). PW Pp continues to run w/ operator lock out until SEC reset.
• Mode I: If in Dilute or Alternate Dilute when SI mode op occurs the PW Make Up Pp keeps running and valves CV179/181/185 stay open until PW Flow Controller reaches its shutdown point, valves close at the end of the cycle. The PW Pp will continue to run if SEC not reset, if SEC has been reset by the time the Flow Controller is done the Pps will shut off.
• Mode II, III, IV: SEC shifts control to manual and trips Pp Breaker. Prevents auto start and potential dilution of RCS by imposing operator Lock Out.

PWST

Function and Specs

Function: to supply (fill or make up to) the following loads- CVCS, PRT, RCP Standpipe, SRST, BAE, Sluicing.

Specs:

250,000 gallons, maintained at 35 F

Hi Level 99% (44.5 inches)

Lo Level 7% (3 inches)

Overflow at 45 feet

Normal Line Up: One Pp in manual stop, Second pump in auto stop (Pp starts when make up system demands and trips on Lo-Lo Level of 5% PWST level

Pps Trip on Motor Overcurrent

(SEC response was covered on the Make Up Cards)

BAT and BA Pps

Function and Specs

system consists of two types of tanks and associated Pps and Piping, designed for 150 psig and 200F.

Batch Tanks- purpose to mix Boric Acid and Water; 400 gallons stainless steel, 300F tank temp and level alarms

Boric Acid Tanks (2)- 8000 gallons each, heated to ensure 63 F (TS Value) with air at 40 F; heaters turn on at 70 F and turn off at 80F, no low level trips, heaters are unconvered at 11.6%.

Boron Concentration (4% by weight) or 6990 ppm, to meet TS required 3.75% by weight Boron.

Boric Acid Transfer Pps- 2 speeds, slow used for tank recirc (37.5 gpm) and fast used for chemical addiitons, (75 gpm)

Normal Operation: 1 Pp manual stop, 1 Pp auto, slow

Trips: Motor Overcurrent

Power Supplies

21 BAT Pp 460 V AC, A Bus

22 BAT Pp 460 V AC C Bus