Rcp's Flashcards
Purpose of RCP’s
- provide flow to transfer heat from core to S/G’s
- h/u RCS from cold plant conditions
Describe RCP’s
- 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)
Labyrinth Seals function
- minimize flow through thermal barrier if seal injection lost
- divert flow past hx tubes instead of along shaft
Thermal Barrier /therm barr hx function
- 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
Radial bearing function
- constrains pump shaft against lateral movement
Describe flow rates/ pressures of seal injection
- 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
- 3 gpm past #1 seal.
- 800 cc/ hr to #3 seal (primary water from 7 ft standpipe)(3psig)
- 400 cc/ hr to RCDT
- 400 cc/ hr to structure sump
What disadvantages are there to loosing seal injection?
- 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)
Describe #1 seal
- 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
Describe the low leakage shutdown seal (sds)
- 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
Describe #2 seal
- 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
Describe #3 seal
- 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
Describe CVCS-8141 A/B/C/D
- Isolates seal return from #1 seal outlet to cvcs.
- done when #1 fails => ensure all flow goes to #2 seal turning into film riding
Describe CVCS-8100/ 8112
CNMT isolation for seal return (phase A)
Describe RCP motor
- 12 k flywheel increase coast down time
- anti-reverse rotation (prevents excess starting currents)
- air cooled
RCP’s power supplies
1-1 (12kv) E
1-3 (12kv) E
1-2 (12kv) D
1-4 (12kv) D
RCP trips
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)
Interlocks required to start RCP
- 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
How does CCW interface with RCP’s
- 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
Precautions and Limitations for RCP’s
- 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
- Lpzr < 50%.
- minimize ops of 1-1 & 1-3 below 350 deg
Precautions and limitations for opening seal #1 bypass (CVCS-8142)
Why would you do this?
- 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
