Mode 3 to Mode 5

Question 1

Describe the scope of 40OP-9ZZ10 Mode 3 to Mode 5 operations

Answer 1

• Stabilizes the plant in Mode 3 to set up for cooldown or start-up
• Plant cool down to Mode 5.
• Secondary plant shutdown while using the EOP

Question 2

State the precaution associated with RCS heat addition or removal methods.

Answer 2

• Changes to RCS heat addition or removal methods (RCPs, SGs and ADV/SBCS, etc.) should be made by only one method at a time and sufficient time allowed for accurate indication temperature change before making the adjustment.

Question 3

State the precautions associated with performing dilutions while subcritical.

Answer 3

• Anticipate criticality for any dilutions
• Stop dilutions if power / count rate doubles
• EOL: large dilutions required to achieve Estimated Critical Boron Concentration (ECBC).
  
  • Dilution is allowed to start as long as final C_b is maintain 50 ppm > ECBC or 50 ppm > SDM C_b.

Question 4

State when PZR boron equalization is required to be performed.

Answer 4

• RCS/PZR boron equalization started if RCS boron changed by 50 ppm. Maintain ≤ 10 ppm difference.

Question 5

What is the SDM boron concentration admin limit and why is it in place?

Answer 5

• Admin boron limit is maintain 100 ppm above required SDM boron.
  
  • Compensates for changes in NCW / letdown temperatures

Question 6

State the auto features associated with PZR level temperature compensation.

Answer 6

• LT-110X/110Y (hot cal) / LT-103 (cold cal) PZR level
  
  • LT-110X/Y: if colder than 653°F/2250 psia, indicated will be higher than actual (swaps < 20%)
  • LT 103: if hotter than 60°F/14.7 psia, indicated will be lower than actual (swaps < 20%)

Question 7

WHen is LTOP required to be placed in service?

Answer 7

• LTOP required when any Tcold is ≤ 221°F (Both SDC suction relief valves in-service)

Question 8

State the temperature requirements associated with SDC:

• SDC design limit:
• LPSI pump seal temperature limit:
• Extended SDC operations temperature limit:
• CS pump to SDC temperature/pressure limits:

Answer 8

• 350°F – SDC design temperature limit (FSAR)
• To extend LPSI Pump seal life, SDC normally initiated when RCS is < 300°F. (SM permission to align > 300°F)
• Extended SDC ops (> 4 days), should be performed at ≤ 135°F
• CSP cannot be aligned to SDC until ≤ 200°F / ≤ 250 psia. (Limits prevent pump damage.)

Question 9

What is a concern when venting from penetration rooms when in midloop conditions?

Answer 9

Venting may introduce air into SDC System.

Question 10

State the CHP pulsation dampener precharge pressure limitations.

Answer 10

• Charging Pump pulsation dampener precharge pressure should be maintained at ~ 60% of charging operating pressure and will always be maintained at 25-75% of charging system pressure.

Question 11

State the requirements of LCO 3.6.6 CS system.

Answer 11

• LCO 3.6.6 requires both trains of CS to be operable Modes 1-4 ≥ 385 psia.
  
  • One train of CS is required to be available until Mode 5 entry (PRA requirement)
  • Due to not having class CTMT HVAC. LOCA in Mode 4 < 385 psia may not be covered.

Question 12

Why are generator PCBs limited to 2 hours of being energized and open?

Answer 12

• Generator PCBs (935/938) should not be open and energized for > 2 hours.
  
  • Reduces life or causes premature break down of the surge capacitors which are shunted to the breaker contacts.
  • Reclose for SWYD reliability (ring bus)
  • U1: Switching may cause a drop in voltage (3kV). If SIAS present, it could load shed WRF.

Question 13

What could occur if RCS pressure is lowered below the shutoff head of the RMW pump?

Answer 13

• ↓ RCS pressure below shutoff head of RMW pump may allow an uncontrolled dilution of the RCS.

Question 14

State the max amperage to the following MFW pumps:

AFA:

AFB:

AFN:

Answer 14

It’s steam driven…

151 amps

122 amps

Question 15

What is a consequence of extended use of AFNP01 when SG lvl is < 27% NR?

How is this avoided?

Answer 15

• Extended use of AFW to maintain ≤ 27% NR may damage the downcomer feed ring and piping. Lines become voided < 27%. Minimize voiding and water hammer.
• Feed ≥ 250 gpm until > 27% NR
  
  • < 250 gpm – potential water hammer

Question 16

D/C isolation block valve dP is limited to > 600psid.

Why?

Answer 16

It may prevent valve closure.

Question 17

State the RCP operational limits associated with pump combinations.

Answer 17

• RCPs 1A and 1B are the preferred pumps to leave running to maintain max Spray capability.
• If SG forced cooldown will be performed, keep 1A/2A running or 1B/2B running.
• Avoid running 1A and 2B or 1B and 2A. Minimizes RCP journal bearing damage.
• To prevent lift, RCPs are limited to 3 or less when temp is < 500°F.
• For P-T concerns, only two RCPs are allowed < 200°F

Question 18

State the natural circulation flow indications and what successful nc flow looks like.

loop dT

Thot

Tcold

CET SCM

dT between Thot and max CET

Answer 18

• < 65°F Loop ΔT
• Thot ↔ or ↓
• Tcold ↔ or ↓ (should be at Tsat for SG pressure)
• ≥ 24°F CET SCM
• < 30°F ΔT between Thot and max CET

Question 19

What shoudl automatically occur at < 1x10-4%?

What must be done prior to <1x10-5%

and <=2x10-6%?

Answer 19

• < 1x10^-4%: ensure high log power bypasses automatically removed (red/white lights off)
• < 1x10^-5%: bypass CPC trips
• ≤ 2x10^-6%: energize start-up channel NIs (select SU NI, press HV Permit/HV On button)
  
  • BDAS channel checks within 1 hour

Question 20

State the major evolutions associated with staying in Mode 3 operation.

Answer 20

• Re-ring the SWYD bus. (Close PCBs within 2 hours)
• Maintain Tcold < 570°F
• If Tcold is lowering, Close MS drains if MSIVs are open and stop SGBD
• Align BFT to the condenser
• Restart RCPs if required
• Secure HDTPs if running
• Cooldown feedwater lines if MFW is in-service.
• Place an AFW pump in-service (AFN→AFB→AFA)
• Secure the MFW pumps
• Maintain SGWL 30-50% NR
• Restore vacuum / CW if required
• Restore the Main Steam lines / SBCS if required:
  
  • 75°F/hour steam line HUR limit
  • < 15°F/hour RCS CDR limit when warming the steam lines
• Align Turbine / generator support systems
• Stop all but one Condensate pump
• Evaluate placing long path recirc in-service (short M3 entry followed by start-up, secondary pressurized, vacuum maintained)
• Maintain SDM

Question 21

What should be first bypassed during cooldown to Mode 5?

Answer 21

DAFAS

Question 22

When are D/C control valves isolated and control of feed swapped to bypas mov’s?

Answer 22

• Isolate DCCV when control becomes unstable. Feed with bypass MOVs.

Question 23

When do we begin establishing the correlary boron concentration for cooldown?

Answer 23

• Prior to commencing cooldown, begin establishing initial RCS boron concentration for cooldown (Target ~270°F: SDC entry temperature - 20°F)

Question 24

What is the preferred AFW pump operation?

Answer 24

• Place AFW pump in-service (AFN→AFB→AFA)

Question 25

How many MAIN spray valves should be used for RCS cooldown?

Answer 25

ONE

Question 26

What method is used to initially cooldown the RCS?

Answer 26

• Start RCS cooldown and depressurization
  
  • Use SBCVs or ADVs
  • Thottle open one spray valve to maintain constant pressure reduction (throttling will minimize thermal stresses when < 4 RCPs are operating).

Question 27

What precautions associated with lowering Low Ppzr setpoints must be observed before lowering the setpoint?

Answer 27

• If Tc is ≥ 485°F, maintain setpoint ≥ 140 psia above Tc saturation pressure. Ensures SIAS prior to upper head void formation in the event of RCS depressurization caused by a SLB. (LCO 3.3.5 bases)
• If exceeded, raise RCS pressure or cooldown to < 485°F within 2 hours.
• If pressure is too low for the existing temperature, and an accident occurs, saturation conditions could exist in the RCS before the new, lower SIAS setpoint is reached. When saturation conditions occur, the pressure drop due to the LOCA is greatly reduced as water flashes to steam and holds the pressure up. This could prevent (or delay) the SIAS actuation and HPSI injection. Maintaining the setpoint 140 psia above saturation pressure ensures proper SIAS and HPSI injection.

Question 28

At what temperatures are RCPs nomrally stopped?

Answer 28

• ≤ 505°F: Stop one RCP
• ≤ 350°F: Stop the 3^rd RCP

Question 29

What must be adjusted on the CHPs during RCS depressurization?

Answer 29

• Adjust charging pump pulsation dampener pressure as RCS pressure lowers
  
  • Pump is non-functional during adjustment

Question 30

When is the second LD control valve placed in service?

Answer 30

• < 1050 psia PZR: place the 2^nd letdown control valve in-service

Question 31

Why do we stabilize RCS pressure at 750 psia?

Answer 31

• Stabilize at 750 psia:
  
  • ↓ SIT pressures to 300 psig
  • Place 2^nd letdown back pressure control valve in-service

Question 32

When is the Ppzr low press trip and SIAS actuation bypassed?

When are SITs isolated?

When can the SDC inlet isolations be opened?

Answer 32

• < 400 psia: bypass low PZR pressure trip/SIAS
• 400-380 psia: isolate the SITs
• < 385 psia: Recirc the SDC loop that will be placed in-service

Question 33

What occurs at 300F RCS temperature?

Answer 33

• 300°F: stop the cooldown and perform crud burst clean-up

Question 34

When is SDC placed in service?

If it is desired to place SDC in service above this temperature, whose permission is required?

Answer 34

• Place SDC in-service:
  
  • Tcold < 300°F
  • SM/CRS permission if < 350°F, but > 300°F

Question 35

When are the SGs isolated/shutdown?

What occurs following this?

When can the SGs be placed in wet layup?

Answer 35

• Shutdown Main Steam when SG pressure < 20 psig
• Perform forced cooldown of the Steam Generators. (If required)
• < 227°F: Place SG WLU in service

Question 36

State the remaining major evolutions following placing SG’s in wet layup.

Answer 36

• Shutdown AFW
• 222-227°F Tcold: place LTOP in-service on the loop that is not aligned for SDC
• Reduce RCS pressure to ~ 250 psia.
• Monitor for voids
• Enter Mode 5 when Tc ≤ 210°F
• Commence tracking CTMT penetrations (if SNOW or refueling outage)
• Stabilize at 180°F unless further cooldown is required (performed in outage GOPs)
• Isolate NC CIV relief valve
• De-energize CS MOVs
• HPSI pumps breakers disabled in Mode 5 (LTOP / positive control)
• Go to ZZ23 (refueling outage) or ZZ24 (SNOW outage)