RRCS

Question 1

Hi Pressure initiation logic.
(part of table)

Answer 1

Hi Pressure >1071psig

ARI - Immediate

RPT Trip - Immediate

Feedwater Runback to 2500 RPM (650 RPM IF Speed Control Failure) - After 25 second TD IF APRMs not Downscale or INOP

SLC initiation and RWCU isolation - After 3.9 minute TD IF APRMs not Downscale or INOP

Question 2

Low Level initiation logic.
(part of table)

Answer 2

Low Level <-38”

ARI - Immediate

RPT Trip - After 9 sec TD (Seals in)

SLC initiation and RWCU isolation - After 3.9 minute TD IF RPV level < -38” AND IF APRMs not Downscale or INOP

Question 3

Manual Initiation of logic.
(part of table)

Answer 3

ARI - Immediate

SLC initiation and RWCU isolation - After 3.9 minute TD IF APRMs not Downscale or INOP

Question 4

RRCS initiation logic coincidence.

Answer 4

RRCS has 2 channels. An entire channel must energize to satisfy logic. (2-out-of-2 taken once)

Question 5

SLC Initiation seal in.

Answer 5

High Pressure Seals in, Low Level does not.

Question 6

When can RRCS be reset?

Answer 6

After 13.9 mins.

Question 7

Why can RRCS be reset after 13.9 mins?

Answer 7

3.9 minutes for SLC timer to clear and an additional 10 minutes for the TD logic. If power level goes above 4% or the APRMs become inoperable during the 10 minute seal-in of the RRCS logic, SLC will actuate.

Question 8

When can ARI Logic be reset?

Answer 8

• ARI logic can be reset after 30 seconds. This allows for complete Control Rod insertion.
  a) Reset Light @ 10C651D

Question 9

High Pressure initiation time line.

Answer 9

0 sec - ARI Valves Open, Both Recirc Pump RPT Breakers Trip, RFP, ARI, SLC Timers Start

25 sec - RFPs Runback (2500 RPM)

30 sec - “ARI Ready for Reset” IF High Press Clear

55 sec - RFP control returned to operator in MAN

3.9 min - SLC Initiates IF APRMs INOP or not DNSCL Starts 10 min reset timer

13.9 min - “RRCS Ready for Reset” light

Question 10

Low Level Initiation Timeline.

Answer 10

0 sec - ARI valves open, RPT , ARI, SLC timer starts.

9 sec - Both recirc pump RPT breakers trip

30 sec - “ARI Ready for Reset” If Low Level Clear

3.9 min - SLC Initiates IF APRMs INOP or not DNSCL Starts 10 min reset timer

13.9 min - “RRCS Ready for Reset” light

Question 11

How quickly do rods move/are fully inserted with ARI actuation?

Answer 11

ARI valves are sized so that Rod Insertion will begin within 15 seconds of signal with rods fully inserted by 25 seconds.

Question 12

ARI valves:
Power source and bus
Where are they located in the system?

Answer 12

1. The CRDH system contains 8 valves (4 per RRCS logic channel) which depressurize the scram air header to ensure control rod insertion.
   a) Each valve is 125 VDC, energize to actuate.
   b) Powered from 1AD417 and 1BD417.
   c) One valve per trip channel at each location:
   1. Air Supply header to North Bank HCUs
   2. Air Supply header to South Bank HCUs
   3. Air Supply to the inboard SDV vent and drain valves.
   4. Main CRD Air Header (in line with RPS backup scram pilot valves)

Question 13

Where can RRCS be manually initiated from?

Answer 13

1. 10C651 Switches (“MANUAL INITIATION PERMISSIVE” and “MANUAL INITIATION” PBs @ 10C651D)
   a) Need to depress 2 buttons in EACH sublogic for at least 1 RRCS channel to initiate ARI (during ATWS, 8 total ARI buttons would be depressed).
2. Test Switches in RRCS panels in the upper control equipment room (162’)

Question 14

Purpose of the time delays.

Answer 14

1. 25 seconds for RFP runback – Adequate time to insert control rods
2. 9 seconds for RPT breakers – Simulates coast down of MG set
3. 3.9 minutes (230 seconds) SLC – allows for other methods of power reduction.

Question 15

Loss of the AD483 (BD483)

Answer 15

A loss of the AD483 (BD483) will cause a loss of ‘A’ and ‘C’ (‘B’ and ‘D’) APRM downscale signals to RRCS.

Question 16

RPT breaker trips.

Answer 16

RRCS Channel A (B) controls RPT breakers AN205 (CN205) and BN205 (DN205) – Thus either channel will trip both recirc pumps.