Electrical Distribution

Question 1

“LCO 3.8.1 - AC Sources - Operating” requirements

Answer 1

2 off-site sources available

2 EDG’s available

Question 2

What is the required action if 1 off-site source OR EDG is inoperable in modes 1-4?

Answer 2

Perform off-site source checks WITHIN 1 HOUR

Question 3

What is the required action if 3 off-site sources are inoperable in modes 1-4?

Answer 3

IMMEDIATELY Enter LCO 3.0.3

Question 4

“LCO 3.8.2 - AC Sources - Shutdown” requirements

Answer 4

1 off-site source (startup 1-2 counts) and 1 EDG

Question 5

What is the required action if a required off-site source or EDG is inoperable in modes 5 or 6 or during movement of irradiated fuel assemblies?

Answer 5

IMMEDIATELY Declare affected required features with no off-site sources available inoperable

                        OR

IMMEDIATELY Stop core alterations, suspend irradiated fuel moves, stop all actions that add positive reactivity, and initiate action to restore off-site power source or EDG to operable status

Question 6

What happens to C/D bus on a loss of safeguards bus?

Answer 6

Fast transfer to Startup 1-2

Question 7

What happens if C and/or D bus being supplied by its respective diesel, and the plant trips?

Answer 7

EDG output breaker opens, load shed, output breaker re-closes, and shutdown sequencer loads the EDG.
EDG doesn’t trip

Question 8

What happens on a 2400 volt bus overcurrent?

Answer 8

Trip and lockout incoming breakers

Lock out EDG output breakers

Question 9

What happens on a 2400 volt bus ground?

Answer 9

Control Room alarm only. No automatic actions

Question 10

What happens on a 2400 volt bus undervoltage?

Answer 10

Instantaneous (77% of rated voltage) - -Trip incoming breakers, Load shed bus, EDG Starts, EDG breaker closes, Shutdown Sequencer brings loads back one at a time

Sustained (93% of rated voltage) - Degraded Voltage, After .6 seconds EDG Starts, After an additional 6 seconds Under voltage condition still in feeder breakers open and EDG breaker closes, Shutdown Sequencer brings loads back one at a time

Question 11

At what percent power are buses powered from startup vs station power and why?

Answer 11

Startup - less than 20%
Station - greater than 20%

Keeps coastdown feature enabled for as long as possible

Question 12

What is the generator coastdown feature?

Answer 12

prevents Generator output breakers from opening and fast transfer on a plant trip for 10 seconds to allow more time for RCP operation to aid in establishing natural circulation
Blocked when there is a fault on the main generator or transformer

Question 13

What happens on a 4160 volt bus overcurrent?

Answer 13

When Supplied from Start Up Transformers - Trips Start up Power Feeders

When Supplied from Station Power Transformers - Trips Station Power Feeders, Block Fast Transfer, Block Manual closure of feeder breakers

Question 14

What happens on a 4160 volt bus undervoltage?

Answer 14

• Inverse time delay that when times out trips RCPs, Cooling Tower Pumps, and Condensate Pumps to prevent motor damage
• Opens Station Power Feeders and prevents fast transfer and locks out bus to prevent connecting a source of supply to a faulted bus

Question 15

What happens on a station power transformer fault on phase differential?

Answer 15

• Opens all feeder breakers from Station Power Transformers
• Trips Plant (386B relay) – Opens 25F7 and 25H9 no coast down feature
• Buses Fast Transfer to Startup Transformers

Question 16

What happens on a station power transformer fault on sudden pressure?

Answer 16

• Deluge Actuates

- Control Room Alarm

Question 17

What happens on a startup power transformer fault on sudden pressure?

Answer 17

• Deluge Actuates

- Control Room Alarm

Question 18

“LCO 3.8.1 - AC Sources - Operating” applicability

Answer 18

Modes 1-4

Question 19

“LCO 3.8.2 - AC Sources - Shutdown” applicability

Answer 19

Modes 5 and 6, or during movement of irradiated fuel assemblies