Systems Exam 1 - 208/120 & 118 VAC Distribution Flashcards
What do XEC1 and XEC2 supply?
Rated Non-1E, Train C, with regards to nuclear safety, but supply loads required by Technical Specifications.
The main loads are:
→radiation monitoring
→fire protection
→alarm annunciation equipment
Tech Spec 3.7.20 UPS HVAC System Modes 1-4
Two UPS HVAC System Trains shall be OPERABLE (Modes 1-4)
One UPS HVAC System train inoperable
→verify the affected UPS & Distribution Room is supported by an OPERABLE UPS A/C Train immediately
AND
→restore the inoperable UPS HVAC train to OPERABLE status within 30 days
Tech Spec 3.8.7 Inverters Operating (Modes 1-4)
The required Train A and Train B inverters shall be OPERABLE (Modes 1-4)
NOTE: Inverters may be disconnected from one DC bus for ≤ 24 hours to perform an equalizing charge on their associated common battery, provided:
→The associated AC vital bus(es) are energized; and
→All other AC vital buses are energized from their associated OPERABLE inverters
Tech Spec 3.8.8 Inverters Shutdown (Modes 5-6)
The Train A or Train B inverters shall be OPERABLE to support one train of the onsite Class 1E AC vital bus electrical power distribution subsystems required by LCO 3.8.10, “Distribution Systems - Shutdown.” (Modes 5-6)
1 hour or less, actions:
One or more required inverters inoperable
→Declare affected required feature(s) inoperable immediately
OR
→Suspend CORE ALTERATIONS immediately
AND
→Suspend movement of irradiated fuel assemblies immediately
AND
→Suspend operations involving positive reactivity additions that could result in loss of required SDM or boron concentration immediately
AND
→Initiate action to restore required inverters to OPERABLE status immediately
Tech Spec 3.8.9 Distribution System Operating (Modes 1-4)
Train A and Train B AC, DC, and AC vital bus electrical power distribution subsystem shall be OPERABLE (Modes 1-4)
One AC electrical power distribution system inoperable
→restore AC electrical power distribution subsystem to OPERABLE status within 8 hours
Two trains with inoperable distribution subsystems that result in a loss of safety function
→enter TS LCO 3.0.3 immediately
Tech Spec 3.8.10 Distribution System Shutdown (Modes 5-6)
The necessary portion of the Train A or Train B AC, DC, and AC vital bus electrical power distribution subsystems shall be OPERABLE to support one train of equipment required to be OPERABLE. (Modes 5-6).
1 hour or less, actions:
One or more required AC, DC, or AC vital bus electrical power distribution subsystems inoperable
→Declare associated supported required feature(s) inoperable
OR
→Suspend CORE ALTERATIONS immediately
AND
→Suspend movement of irradiated fuel assemblies immediately
AND
→Suspend operations involving positive reactivity additions that could result in loss of required SDM or boron concentration immediately
AND
→Initiate actions to restore required AC, DC, and AC vital bus electrical power distribution subsystems to OPERABLE status immediately
AND
→Declare associated required residual heat removal subsystem(s) inoperable and not in operation immediately
What supplies DRPI?
How is it interlocked?
uC14 supplies DRPI, normally powered from uC1 but can be fed from uC4
normal and alternate power supplies mechanically interlocked
How is the spare inverter supplied?
What can the spare inverter supply?
How does it provide this supply?
The spare inverter can be supplied from either train related DC bus or dirty power.
It can supply power to any of the 4 train related Instrument buses.
Through the appropriate inverters being replaced via removing from service a static transfer switch on the inverter itself.
When uEC1 and uEC2 are on Bypass power, their train related Blackout Sequencer is…
Inoperable
→on a loss of offsite power the sequencers will de-energize.
→also on a loss of power to these panels the EDG will trip if running normally and not start in auto or manual due to 86-2
→it will however start in Emergency Manual or SI.
What occurs on a loss of EC1 and EC2?
(Unit difference)
Unit 2 Only
Loss of 2EC1 or 2EC2 will result in:
→loss of Water Hammer interlocks, resulting in
→Feedwater Isolation, and requiring a
→Manual Reactor trip
(Unit 1 doesn’t have water hammer interlocks because of SG replacement)
What causes a fan failure alarm in an inverter cabinet?
→one or both cabinet cooling fans not running
→high ambient temperature
→component failure leading to high cabinet temperatures
Static Switch Auto Transfer Criteria
→DC input voltage ≤105 VDC
→AC output voltage drops to 50% normal value (~59 VAC)
→Output load current rises to 120% of rated value (~175 Amps)
What do uC5 and uC6 supply?
→Plant Computer
→MFP and Condensate Polishing Digital Controls
→SSII
→AMSAC
→Electronic Kilowatt-Hour Counter Panel
AC Essential Lighting
(powered from 480 VAC via step down transformers)
Supplies lighting in areas essential to the safe shutdown of the plant (ECB, Aux Bldg, U1 and U2 SFGDs)
DC Emergency Lighting
Provided as a backup to AC lighting systems in locations where safety related functions are performed and for personnel safety in access and egress routes
In areas where the DC Emergency Lighting is provided, 8-hour rated battery packs or station batteries are provided
Security Lighting
Power to the lights on masts is split between Train A and B so that on a loss of a single train only half the lights are lost
Aviation Obstruction Lighting
If normal power is lost (1E), an automatic transfer switch in each flasher controller will energize ALL the lamps from 125 VDC (XD2-2).
(bypasses photocell, flasher and spare lamp transfer relays)
118 VAC Operability
→The individual distribution panels must be powered from an inverter which is supplied from a 125 VDC bus.
→When the swing inverter is used it must be supplied from the same DC bus as the inverter it is replacing.
→The off-going inverter must be removed from the DC bus prior to placing the swing inverter on the same DC bus.
