Class 125V DC

Question 1

A LOP has occurred on PBA-S03. DGA has since sequenced unto the bus. What happens on a loss of PKA-M41?

Answer 1

Diesel trips and cannot be restarted. The diesel output breaker must be locally opened due to loss of control power, or the diesel generator will turn into an induction motor and damage to the machine will occcur.

Question 2

AFA is running feeding both SGs. What will be the effect of a loss of PKA-M41 on AFA feed pump?

Answer 2

Without control power, the governor for AFA will fail open and cause AFA to trip on over speed.

Question 3

What ECCS valves will we lose the ability to operate on a loss of their respective PK busses?

Answer 3

SDC suction isolation valves SIC-UV-653, and SID-UV-654, and long term HPSI cooling valves SIC-UV-321 and SID-UV-331.

Question 4

How does a loss of PKB affect the ADVs?

Answer 4

Power to the permissive solenoids for the ‘B’ train ADVs will not be available, leaving only one ADV per S/G available.

Question 5

How does a loss of PK affect PN in each Unit?

Answer 5

In Unit 1, power to PN must be restored locally by manual transfer of the power supply. In Units 2 and 3, a static transfer switch will transfer power from the DC/AC inverter to the backup voltage regulator.

Question 6

How is shifting battery charges for PK different than NK?

Answer 6

PK does not have a load sharing circuit like NK does, so when transferring PK the sequence is break before make. NK is make before break.

Question 7

What must happen prior to placing a PK battery on an equalizing charge?

Answer 7

Power to PN must be transferred from the inverter to the voltage regulator to prevent damage to the inverter.

Question 8

How can the control room determine which class DC bus is being powered from a swing charger?

Answer 8

There is a small normally green indication under the control for the battery breaker that will be red for the bus with a swing charger aligned.

Question 9

What prevents alignment of a swing charger to more than bus at a time?

Answer 9

A mechanical interlock physically blocks operation of the the open breaker on the side of the swing charger.

Question 10

How many battery cells are in each class battery and what is their configuration?

Answer 10

60 cells, in series.

Question 11

How is battery capacity maintained?

Answer 11

Batteries are maintained on a float charge from the battery charger, and are periodically placed on equalizing charge.

Question 12

What are the main loads off of PKA?

Answer 12

Control power for ‘A’ class switchgear (breaker control power comes from PKA-D21), PNA inverter, AFA steam supply valves and feed flow stop and control valves, D21 panel, ‘A’RTSG breaker control power.

Question 13

What is the status of the closing spring on a closed battery breaker?

Answer 13

Charged.

Question 14

Are the PK busses grounded or ungrounded?

Answer 14

Ungrounded.

Question 15

Why are ground detectors necessary for PK busses?

Answer 15

PK busses are ungrounded, which means ground detection must be accomplished with a detector.

Question 16

What controls are available in the control room related to PK?

Answer 16

Battery breakers can be operated from the control room, that is all.

Question 17

What SESS indications are available for PK?

Answer 17

Battery breaker open or not operable for each PK bus.

Question 18

What normally cools the DC equipment rooms?

Answer 18

Air is normally supplied by ESF switchgear normal AHUs, and is removed by the Control Building Normal AHU.

Question 19

Upon a SIAS or a LOP, what cools the DC equipment rooms?

Answer 19

The DC Equipment room essential AHUs.

Question 20

How many PK buses have LOCAL/REMOTE Disconnect switches?

Answer 20

3. PKA-M41, PKB-M42 and PKD-M44.

Question 21

What Safety Injection valves are powered from PK?

Answer 21

SIC-UV-321, SID-UV-331 (HPSI long term cooling)

SIC-UV-653, SID-UV-654 (Shutdown cooling suction isolation valves)

Question 22

Is the PK system grounded?
A) No
B) Yes
C) Maybe
D) All of the above

Answer 22

A) No

Question 23

With a Class battery charger INOPERABLE, what action is required within one hour?

Answer 23

LCO 3.8.4.C.1- Verify battery cell parameters met Table 3.8.6-1 category A Limits.