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Block 2 > Chemical and Volume Control System > Flashcards

Chemical and Volume Control System Flashcards

1
Q

Discuss Letdown basic Design.

A

Letdown originates from the B1 Intermediate Leg

Unit 1
Two valves in series.
V2515 & V2516 are both Inside CTMT

Unit 2
Three valves in series.
V2515 & V2516 are Inside CTMT.
V2522 is Outside CTMT

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2
Q

Discuss Letdown Isolation Valve V2515

A

Unit 1
Shuts on (any of the following):
* SIAS
* CIAS
* T>470F as sensed on TIC-2221
(Indicative of a loss of CHG – alarms @ 460F)
* All fail closed on loss of air or power.

Unit 2
Shuts on (any of the following):
* SIAS
* T>470F as sensed on TIC-2221
(Indicative of a loss of CHG – alarms @ 460F)
* All fail closed on loss of air or power.

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3
Q

Discuss Letdown Isolation Valve V2516.

A

Unit 1
Shuts on:
* SIAS
* CIAS
* D/P >275 psid across RHX
(Indicative of a L/D line rupture d/s of RHX)

Unit 2
Shuts on:
* SIAS
* CIAS
* D/P >275 psid across RHX
(Indicative of a L/D line rupture d/s of RHX)

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4
Q

Discuss Letdown Isolation Valve V2522.

A

Unit 1
Does not exist on Unit 1.

Unit 2
Shuts on:
* CIAS

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5
Q

Discuss the Regenerative Heat Exchanger (RHX).

A

Preheats charging flow – minimizes thermal stresses on the charging connection to the RCS
Helps cool letdown flow (~ 550 °F to ~270 °F)
RCS letdown flows thru tube side
Charging flows through the shell side
Since CHG is at a higher pressure (~2300 psia vs. 2250 psia RCS pressure) a RHX tube leak would result in CHG flowing into letdown line

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6
Q

Discuss Letdown Level Control Valves LCV-2110P & 2110Q.

A

Controlled by the PZR Pressure & Level Control System to maintain PZR level
Even though these valves maintain PZR level, the first major reduction in Letdown Pressure occurs across these valves (2250 psia – 430 psig) due to their throttling characteristics.
Normally one valve in service when RCS > 1400 psia.
Place the 2nd valve in service when RCS pressure < 1100 psia.

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7
Q

Discuss Letdown Level Control Valve Control Location.

A

Controlled from RTGB: “P” – “Both” – “Q”

Unit 1
Both valves capable of control from HSP

Unit 2
Only the P valve control is available from the HSP

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8
Q

Discuss Letdown Limiter LY-1110

A

Limits the position of the LCVs in order to maintain flows between 29 and 128 GPM
29 GPM: Occurs @ – 1.0% level deviation
128 GPM: Occurs @ +9.0% level deviation.
Can be bypassed, allows the LCVs to be fully opened or closed to aid in re-establishing letdown flow

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9
Q

Discuss Letdown Pressure Control Valves PCV-2201P and PCV-2201Q

A

Maintains a backpressure of pressure at 430 psig upstream of the PCV’s
Prevents flashing from occurring prior to letdown flow going through the LDHX, as there is a major pressure reduction across the LCV’s
Can Bypass to charge faster when going solid with a Keyswitch

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10
Q

Discuss Letdown Pressure Control Valve Control Location.

A

Controlled from RTGB: “P” – “Both” – “Q”

Unit 1
Both valves capable of control from HSP

Unit 2
Only the P valve control is available from the HSP

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11
Q

Discuss Letdown Temperature Indication and Control.

A
  • Temperature is sensed upstream of the Pressure Control Valves
  • TIC-2223: Senses L/D temperature and controls position of TCV-2223 which adjusts CCW flow to L/D HX
  • Reverse-Acting Controller:
     0% output is calling for TCV-2223 to be full open
     100% output is calling for TCV-2223 to be full closed
     Remember the effects of temp changes on IX’s (i.e. “Cold sucks”) and how they may affect SDM
  • Alarms at 135F
  • TE 2224 - High Temp @ 140F: positions V2520 to automatically bypass the CVCS Demineralizers to protect the resin
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12
Q

Discuss Letdown Relief Valves.

A

Discharge to the relief valve collection header

Unit 1
* V2345 Set pressure is 600 psig

Unit 2
* V2345 Set pressure is 600 psig
* TIA-6660, on the downstream relief line.
* TIA-6660 will actuate annunciator LC-15 on PACB #2 on high temperature 200F

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13
Q

Discuss Letdown Radiation Monitor.

A
  • Used on Unit 1 only
  • Channel 40 Gross Activity
    • indicates Crud Burst if alarming during power changes
  • Channel 41 Iodine
    • indicates Fuel Clad failure when alarming during steady state conditions
  • Fuel Clad Failure will cause both alarms
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14
Q

Discuss Letdown Divert Valve V2500.

A

Control Switch Positions:
“VCT – Auto – WMS”
With Control switch in:
“VCT” - Flow to VCT only
“Auto” - VCT or WMS automatically based on VCT level program
“WMS” - Flow to WMS only
Waste Management flowpath
Normally aligned to in-service HUT
Alternate path – Flash Tank

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15
Q

Discuss the Volume Control Tank.

A
  • 4200 gallon tank. 33.8 gals/%
  • ~27-29 psig H2 overpressure normally maintained. Scavenges oxygen. Swapped to N2 during outages (If <20 psig, risk getting oxygen entrained in Charging pump suction)
  • RCS surge volume & NPSH for charging pumps
  • High Temp alarm at 130F
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16
Q

Discuss VCT Level Transmitters.

A

LT-2226:
* Indication on RTGB & DCS.
* Provides Auto Makeup Function, and Hi/Lo Level Alarm
LT-2227:
* Indication on DCS only. (If LT fails, would get divert/swap without indication on RTGB for level issue)
* Provides Auto Divert Function, Swap To/From RWT, Lo-Lo Level Alarm

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17
Q

Discuss VCT Outlet Valve V2501 and RWT to Charging V2504.

A

On SIAS:
V2501 – Closes
V2504 – Does not reposition

On VCT level of 5% and lowering Swaps to RWT:
V2501 – Closes
V2504 – Opens

On VCT level of 15% and rising Swaps from RWT:
V2501 – Opens
V2504 – Closes

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18
Q

Discuss VCT Level Program.

A

Hi level Alarm (LT-2226) 90 % 94 %

Auto Divert to WMS begins via V2500 (LT-2227) 88 % 92 %

Auto Divert to WMS secures (LT-2227) 88 % 83 %

Auto Makeup secures (LT-2226) 55 % 54 %

Auto Makeup starts (LT-2226) 40 % 40 %

Low Level Alarm (LT-2226) 35 % 37 %

Charging Pump suction swaps back to VCT (LT-2227) 15 % 15 %
* V2504, RWT to Charging Valve, closes
* V2501, VCT Outlet Valve, opens

VCT Lo-Lo Level Alarm. 5 % 15 %

Charging Pump suctions swaps to RWT (LT-2227) 5 % 5 %
* V2504, RWT to Charging Valve, opens
* V2501, VCT Outlet Valve, closes

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19
Q

What are the VCT High Level alarm setpoints?
LT-2226

A

Unit 1
90%

Unit 2
94%

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20
Q

What level does VCT Auto Divert to WMS begin via V2500?
LT-2227

A

Unit 1
88%

Unit 2
92%

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21
Q

What level does VCT Auto Divert to WMS via V2500 secure?
LT-2227

A

Unit 1
88%

Unit 2
83%

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22
Q

What level does VCT Auto Makeup secure?
LT-2226

A

Unit 1
55%

Unit 2
54%

23
Q

What level does VCT Auto Makeup start?
LT-2226

A

Unit 1
40%

Unit 2
40%

24
Q

What level does Charging Pump Suction swap from VCT to RWT?
LT-2227

A

Unit 1
5%

Unit 2
5%

25
Q

What level does Charging Pump Suction swap back to VCT from RWT?
LT-2227

A

Unit 1
15%

Unit 2
15%

26
Q

At what level does the VCT Low Level Alarm Acuate?
LT-2226

A

Unit 1
35%

Unit 2
37%

27
Q

At what level does the VCT Lo-Lo Level Alarm actuate?

A

Unit 1
5%

Unit 2
15%

28
Q

What is the Charging Pump nominal flowrate?

A

44gpm per pump

29
Q

What are the Charging Pump power supplies?

A

A - A2 480V LC
B - B2 480V LC
C - AB 480V LC

30
Q

Discuss the RTGB Control Switches for the Charging Pumps.

A
  • STOP – AUTO – START positions
  • Maintains in STOP – Pump considered inoperable while switch in STOP

Unit 1
* Spring returns to Auto after taken to start

Unit 2
* Has a “Hard Start” Position on the Hand switch – does not spring return to Auto

31
Q

Discuss Charging Pump Backup Selector Switch.

A

Unit 1
* Indicates 1st & 2nd backup CHG pumps
* 1A-1B / 1B-1C / 1C-1A

Unit 2
* Indicates running & backup CHG pumps (U2 is a 2 pump unit)
* 2A-2B / 2B-2C / 2C-2A

32
Q

Discuss Charging Pump Auto Starting Logic.

A

Unit 1
* SIAS – Start signal sent to all 3 pumps
* PZR level signal – start signals sent to backup pumps as level lowers

+4% ↑ (3.6) Backup pumps receive B/U stop signal
-1% ↑ 1st Backup pump stops
-2% ↑ 2nd Backup pump stops
-3% ↓ 1st Backup pump starts
-4% ↓ 2nd Backup pump starts
-5% ↓ All Charging pumps receive B/U start

Unit 2
* SIAS – All 3 pumps get SIAS start signal but only A&B pumps normally start.
The 2C pump will start in place of the A or B only if the pump on the side it is electrically tied to is disabled by placing handswitch in STOP.
* PZR level signal – start signals sent to backup pumps as level lowers

+4% ↑ (3.6) Selected B/U pump receives a B/U stop signal
-1% ↑ Selected B/U pump stops
-2% ↑ N/A
-3% ↓ Selected B/U Pump Start Signal
-4% ↓ N/A
-5% ↓ Selected B/U Start signal to B/U pump

33
Q

Discuss Charging Pump Trips.

A

Unit 1
Low Suction Pressure @ ≤ 10 PSIA
* Bypassed by SIAS signal
* On SIAS, when BAM Tanks empty – CHG Pumps become gas bound if no action taken

Unit 2
Low Suction Pressure @ ≤ 10 PSIA
Low Oil Pressure @ ≤ 4 psig
* Trips NOT bypassed by SIAS signal. Recirc fully opens then pump stops
* On SIAS when BAM Tanks empty – CHG Pumps trip on Low Suction Pressure
* Low Oil Pressure is an input to the CHG Pump Trouble Alarm

34
Q

Discuss Charging Pump Recirc Path.

A

Unit 1
No Recirc path back to VCT

Unit 2
Charging Pump Recirculation MOV’s back to VCT
* Valves are OPEN when the pump is secured.
* When CHG Pump is started, the Recirc MOV’s begin modulating closed over a ~ 3 minute interval. As they close you should see CHG flow rising towards ~44 gpm.
* If CHG PP running on PPLCS signal, and PZR level has reached an auto stop setpoint, the recirc valves start to open. When full open, CHG PP stops
* CHG PP will immediately stop if Control Switch taken to stop, but recirc valves will begin stroking open. If pump is re-started (manually or PPLCS) before the recirc valve has fully opened, then pump will trip once the recirc is fully open.
* If a SIAS occurs while a recirc valve is opening or closing, the valve will stop moving, have a 2 second time delay, and then start closing

35
Q

Discuss the impact of the Unit 1 1C Charging Pump U/V Trip.

A

If the 1C Charging Pump is running, and a LOOP occurs – it will not re-start when the bus is re-powered. PZR level will begin to drop and the selected B/U PP’s will start on a level deviation.

If a LOOP & SIAS occur, the 1C Charging Pump will restart automatically at the 18 second load block

36
Q

Discuss the Alternate Charging Path.

A

Procedurally addressed in 1(2)-AOP-02.03, Charging & Letdown
* Used if there is a break in the normal Charging flowpath.
* Letdown is isolated, as no RHX cooling exists with Charging flow stopped.
* Requires placing all Charging Pumps in stop which requires entry into T/S 3.0.3. This is the 1st T/S entered.

  • Uses “A” HPSI flowpath and causes “A” HPSI to be inoperable when in use. T/S 3.5.2 must be entered also.
  • If break downstream of Manual Header Isolation V2429 any charging pump can be used
  • If the break is upstream of the Manual Charging Header Isolation Valve V2429:
     Only 1A [2C] Charging Pump can be used
  • RCS pressure must be maintained less than 2250 psia to use this flowpath – prevents lifting a relief valve
  • Results in an RCS boration of up to 650 gal
37
Q

Discuss CVCS Additional Automatic Actions.

A

Additional CVCS automatic actions – Know these
* MV2525 (Load Control) Closes on SIAS
* MV2512 (normal boration) Closes on SIAS
* FCV2161 (U1 borate line) Closes on SIAS
* FCV2210Y (U2 borate line) Closes on SIAS
* {V2510 & 2511 (BAMT recirc)} Closes on SIAS
* [V2650 & 2651 (BAMT recirc)] Closes on SIAS
* MV2509 & 2508 (Gravity Feed) Opens on SIAS
* MV2514 (Emergency borate) Opens on SIAS
* SE-01-1 [V2524] (CBO) Closes on CIS
* V2505 (CBO) Closes on CIS

38
Q

Discuss the Boric Acid Batch Tank.

A
  • 636 gallon stainless steel tank is filled with approximately 500 gallons of DI water from the reactor makeup water system and then heated to >80F by three 15 KW electrical immersion heaters.
  • Normally, sufficient acid is added to yield a concentration of 4371 to 6119 ppm boron
  • Must be >70F to dump to BAMT
39
Q

Discuss the Boric Acid Makeup Tank (BAMT)

A
  • (2) 9975 gal Level indication sw. controls which RTGB alarm is active, usually TS tank active
  • Concentration: 4371 ppm to 6119 ppm (approx 2.5 to 3.5 weight % BA), Heated
  • Bubbler type level indicators, Lose indication if lose Instrument Air
  • Use {90 gal per %} / [92 gal per %] for calculations
40
Q

Discuss Boric Acid Pumps.

A
  • Pumps start on SIAS, unless in OFF (switches do have a hard stop), Recirc Valves close on SIAS
  • Power Supplies: - Know how loss of power on either bus would affect boration capability
    ‘A’ Train:
     A & B BAM Pumps - MCC A6
     Emergency Borate Valve (MV-2514) - MCC A5
    ‘B’ Train:
     Gravity feed valves (MV-2509 & 2508) - MCC B5
     VCT Outlet Valve (MV-2501) - MCC {1B5} / [2B6]
41
Q

Discuss the Normal Boric Acid Blended Flow Path.

A
  • BAM Tank - BAM Pump - FCV-2161 / V2161 - FCV-2210Y - blend header and combines with the PMW (if any) and then normally continues on to the RCS via V2512 (To VCT – normal method for maintaining steady state power) or MV-2525 (To CHG PP suction via VCT outlet piping – if more rapid power change is needed).
  • The normal boration flowpath is automatically isolated by a safety injection actuation signal. This isolation is accomplished by automatic closure of the boric acid header isolation valve FCV-2161 / FCV 2210Y
  • Note: Small additions must chased with ~ 30 gallons of PMW to flush the piping
42
Q

What is the RAB temperature limit and why?

A

Maintain above 55F to ensure Boric Acid does not precipitate out of solution

43
Q

What is the equation for RCS Boron Concentration Change Calculations?

A

V mu = V sys x Ln ((Cmu - Ci)/(Cmu - Cf))

  • RCS volume = {62,500} [66,891] gal Hot or {80,000} [85,600] gal cold
  • ** If you are diluting then concentration of M/U is zero (primary water) **
44
Q

What is the equation for Blended Makeup for the VCT?

A

Blend Ration = (Cbamt / Crcs) - 1

  • 33.8 gallons /% level in VCT
45
Q

Discuss RCS chemistry chemicals.

A
  • Lithium Hydroxide to maintain pH,
  • Hydrogen overpressure on the VCT at power – scavenges O2
  • Nitrogen is used to purge VCT of Hydrogen when shutting down (establish <5 cc/kg)
  • Hydrogen Peroxide added for Crud Burst.
  • Hydrazine – scavenges O2 when shutdown
  • Zinc Acetate is injected to the suction of the Charging Pumps (prevents crud from plating out on piping & component internals)
46
Q

Discuss RCP Controlled Bleedoff.

A
  • The bleedoff flow from each RCP pump passes through an excess flow check valve and enters a common controlled bleedoff header.
  • If this flow should increase to 10 gpm, the respective Excess Flow Check Valve will automatically close and thereby isolate the damaged seal. The check valve will not reopen until the differential pressure across the check valve is reduced to < 30 psid.
  • The combined controlled bleedoff flow then passes through CTMT isolation valves, which close on CIAS:
     SE 01 1 [V2524] (inside CTMT)
     V2505 (outside CTMT)
  • Automatic closure of CBO CTMT isolation valves would result in increased pressure in the bleedoff header upstream of the isolation valves. This can be dealt with by manually opening V2507 (RTGB) which lines up a flowpath to a relief valve (V2199 w/ lift setpoint of 150 psig), that relieves to the Quench Tank.
     V2507 procedurally placed in service following a SIAS / CIAS per Appendix J of 1(2)-EOP-99.
47
Q

Discuss NOP-02.02 – Charging & Letdown.

A
  • Placing a second or third charging pump in service increases letdown flow and may result in general area dose rates in vicinity of letdown line in 19.5’ Pipe Penetration room or 19.5’ Letdown Cubicle room to exceed 1000 mr/hr (Locked High Radiation Area limit) due to reduced transport time of short-lived radioactive isotopes.
  • Changes in letdown temperature directly affect purification ion exchanger resin absorption characteristics. Lowering letdown temperature dilutes the RCS, adding positive reactivity. Raising letdown temperature borates the RCS, adding negative reactivity.
  • MV-02-1, REGENERATIVE HEAT EXCHANGER BYPASS VALVE, is normally OPEN and MV-02-2, CHARGING PUMPS DISCH TO REGEN HX INLET, is normally LOCKED OPEN locally. Both valves are normally de-energized due to Appendix R hot short concerns. Section 7.1.3 Management Directive 5
48
Q

Discuss NOP-02.03 – CVCS Purification System.

A
  • The RCS flow rate shall be greater than or equal to 3000 gpm whenever a reduction in RCS boron concentration is being made per TR 13.1.1, Boron Dilution.
  • When placing a CVCS Ion Exchanger in service in MODE 1 or MODE 2 and the ion exchanger is NOT being used for deboration, then the resin bed must have been borated to within 25 ppm of RCS boron concentration before the effluent is returned to the RCS.
49
Q

Discuss NOP-02.05 - VOLUME CONTROL TANK HYDROGEN AND NITROGEN CONCENTRATION CONTROL.

A
  • VCT pressures below 20 psig could result in gases coming out of solution at the suction of the Charging Pumps. This could result in gas binding of the Charging Pumps.
  • To avoid a potentially explosive mixture, the oxygen concentration in the VCT should be maintained less than 2%
50
Q

Discuss loss of charging or letdown.

A
  • Loss of either requires the isolation of the other.
  • Minimize time without charging/letdown due to RCS inventory reduction from seal leak off.
  • Loss of Letdown while in Solid Plant OPS could cause RCS overpressure event.
  • FSAR assumes operator will secure Charging within 10 [20] minutes of a loss of Letdown to prevent taking the PZR solid.
  • Inability to makeup to RCS.
51
Q

Discuss Loss of Instrument Air affect on CVCS.

A
  • Major effect on CVCS components is Letdown isolation and RCP bleedoff isolation.
  • Many other plant systems affected with complete loss resulting in plant trip.
52
Q

Discuss Loss of ICW or CCW on CVCS.

A
  • Causes CCW temperatures to increase affecting letdown heat exchanger performance.
  • High letdown heat exchanger outlet temperature bypasses the ion exchangers.
  • Letdown isolation valve closes on high RHX outlet temperature.
  • Many other components severely affected by loss of ICW or CCW likely resulting in a plant shutdown or trip (RCPs).
53
Q

Discuss Inadvertent Start of a charging pump while the RCS is solid.

A
  • RCS pressure increase
  • Potential RCS integrity challenge
54
Q

Discuss affect of SIAS / CIS [CIAS] on CVCS.

A
  • Auto actions for boration and containment isolation (of letdown).
  • Charging pumps start
  • Emergency borate valves open (including gravity feeds)
  • VCT suction isolates from charging
  • BAM pumps start and recircs close
  • Letdown line isolates by closure of 2 containment isolation valves. [Unit 2 has 3 valves, 2 of the 3 receive a SIAS signal, 2 of the 3 receive a CIAS signal]
  • Some emergency procedures also call for auxiliary spray as a method for RCS pressure control.

Block 2 (8 decks)

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