Rcp's

Question 1

Purpose of RCP’s

Answer 1

• provide flow to transfer heat from core to S/G’s

- h/u RCS from cold plant conditions

Question 2

Describe RCP’s

Answer 2

• mixed flow pump
• weir plate @ pump discharge ( minimize ECCS backflow during LOCA)
• ~ 90,000 gpm, 280 ft of head ( total 372,000 gpm)(RCS vol 90,000 gal => loop transit time, 15 sec)

Question 3

Labyrinth Seals function

Answer 3

• minimize flow through thermal barrier if seal injection lost
• divert flow past hx tubes instead of along shaft

Question 4

Thermal Barrier /therm barr hx function

Answer 4

• limit heat transfer from RCS ( lose seal inj, 545->140)
• provide valve seating surface (backseat RCP’s) with pump shaft ;
  
  • low pressure coolant isolation
  • leakage isolation into seal package during maintenance

Question 5

Radial bearing function

Answer 5

• constrains pump shaft against lateral movement

Question 6

Describe flow rates/ pressures of seal injection

Answer 6

• 9 gpm below radial bearing. (36 gpm total)(2300psig)
  
  • 3 gpm past #1 seal.
    
    • 3 gpm seal return to VCT (outlet). (12 gpm total)(15-30psig)
  • 6 gpm back to RCS
  • 3 gph past #2 seal
    
    • 3 gph seal leak off to RCDT
• 800 cc/ hr to #3 seal (primary water from 7 ft standpipe)(3psig)
  
  • 400 cc/ hr to RCDT
  • 400 cc/ hr to structure sump

Question 7

What disadvantages are there to loosing seal injection?

Answer 7

• the water going past #1 seal is RCS not CVCS =>
  
  • RCS losing inventory
  • dirtier, debris could damage Seals
  • hotter, must be cooled by thermal Barrier (if CCW lost-> s/d RCP’s)

Question 8

Describe #1 seal

Answer 8

• hydrostatically balanced film riding seal
• minimum d/p 200 psid (255 req by proc) if less (between RCS & VCT
  
  • not enough cooling flow
  • not ensured that two surfaces won’t touch
  • min flow ensures enough cooling to pump radial bearing

Question 9

Describe the low leakage shutdown seal (sds)

Answer 9

• just above #1 seal
• loss seal inj + CCW hot RCS melts wax
• polymer sealing ring grabs shaft reducing leakage <1gpm
• not designed for use during shaft rotation

Question 10

Describe #2 seal

Answer 10

• face rubbing carbon graphite seal
  
  • norm 3 gph flow from 15-30 psig back pressure (vct)
  • # 1 seal failure
    • sees full RCS Press, seal gets distorted to film riding seal
    • new flow ~ 8 gpm
    • acts as b/u to #1 seal

Question 11

Describe #3 seal

Answer 11

• double dam face rubbing seal
• 800 cc/ hr from primary water standpipe (~3 psig)
  
  • 400 cc/ hr downstream to CNMT structure sump
  • 400 cc/ hr upstream to RCDT (with #2 seal leakoff)
• ensures 0 RCS leakage to CNMT

Question 12

Describe CVCS-8141 A/B/C/D

Answer 12

• Isolates seal return from #1 seal outlet to cvcs.

- done when #1 fails => ensure all flow goes to #2 seal turning into film riding

Question 13

Describe CVCS-8100/ 8112

Answer 13

CNMT isolation for seal return (phase A)

Question 14

Describe RCP motor

Answer 14

• 12 k flywheel increase coast down time
• anti-reverse rotation (prevents excess starting currents)
• air cooled

Question 15

RCP’s power supplies

Answer 15

1-1 (12kv) E
1-3 (12kv) E

1-2 (12kv) D
1-4 (12kv) D

Question 16

RCP trips

Answer 16

B/U bkr 
   - man local
   - oc
   - inst. oc
Pri bkr
   - man switch
   - man local
   - 12 kv bus UV
   - 12 kv bus diff (current in = current out)
   - oc
   - RCP bus UF (A)
   - RCP bus UF (B)

Question 17

Interlocks required to start RCP

Answer 17

- rack primary bkr to test
     Or
- b/u bkr closed
- oil lift pump running > 120 sec
- oil lift pressure > 500 psig for 120 sec

With RCP, running oil lift pump will s/d after 50 sec

Question 18

How does CCW interface with RCP’s

Answer 18

• CCW hdr “C” cools thermal Barrier hx and lube oil coolers for brngs
• two headers per pump, one-hx, one-l.o. Coolers
• both isolate on phase B
• hx return header will isolate on hi flow (250 gpm) to protect against RCS leak

Question 19

Precautions and Limitations for RCP’s

Answer 19

• pump radial bearing must be protected when Tave > 150
• seal injection should be in service as long as RCS is pressurized
• RCP seal delta P > 255 psid during RCP operation
• only start one RCP at a time
• do not start RCP when critical
• with LTOP cut in, restrict operation to….
• do not start RCP with cold leg < 283 unless
  
  • Lpzr < 50%.
    or
  • Ts/g < 50 degrees above RCS cold leg
• minimize ops of 1-1 & 1-3 below 350 deg

Question 20

Precautions and limitations for opening seal #1 bypass (CVCS-8142)

Why would you do this?

Answer 20

• radial bearing or seal outlet approaching alarm
• Press RCS 100-1000 psig
• # 1 seal outlet valves open
• # 1 seal leak off < 1 gpm
• seal injection to each RCP > 8 gpm

if your #1 seal is trashed and want to save lower radial bearing