Ts, Ps, and Cs

Question 1

Describe a bistable

Answer 1

Compares input signal to a set point
If OK, power supplies to downstream relay
If not OK, power removed from relay causing trip

Question 2

What are OTDT and OPDT trip logic?

Answer 2

2/4 above the loop specific setpoint

Question 3

What feeds the OPDT and OTDT bistables?

Answer 3

OPDT
Loop-specific setpoint
Loop-specific delta-T
OTDT
Same

Question 4

OTDT inputs?

Answer 4

PZR pressure (one P transmitter for each loop)
Loop-specific AFD
Loop-specific Tavg

Question 5

OPDT inputs?

Answer 5

Loop-specific Tavg

Question 6

What is C3? C4?

Answer 6

C3 is for OTDT
C4 is for OPDT
2/4 are 3% less than setpoint
Blocks outward rod motion
Turbine runback until signal clears

Question 7

P12?

Answer 7

Low-low Tavg
Closes SDs when 2/4 Tavg < 550

Question 8

Where does PZR send protection signals?

Answer 8

PZR high level trip
PZR high P trip
PZR low P trip
P11 block
PZR low P SI
OTDT

Question 9

P7?

Answer 9

Enabled if getting P10 or P13
Flow trips enabled
PZR high level enabled
PZR low pressure enabled

Question 10

P13?

Answer 10

1/2 turbine channels > 10%
Feeds P7 when met

Question 11

What PZR trips are blocked when below P7?

Answer 11

PZR high level
PZR low pressure

Question 12

What causes FW isolation (FWIS)?

Answer 12

SIS
P14 (2/4 > 78% on 1/4 SG)
SG lo-lo level on 2/4 in 1/4 SG
Low Tavg (P4 plus 2/4 Tavg < 564)

Question 13

What will trip the FW pumps? (differs from FWIS)

Answer 13

SIS
P14 (2/4 > 78% in 1/4 SG)
All condensate pumps tripped
High discharge P

Question 14

List C1 - C5

Answer 14

C1: stops outward rod motion when 1 IR > 20%
C2: stops outward rod motion when 1 PR > 103%
C3 & C4: runback when OTDT orOPDT < 3%
C5: Rod withdrawal in auto is blocked when Pimp is <15%

Question 15

What makes something a P or a C?

Answer 15

A P is generated in the SSPS and is safety grade and can be credited.

A C is outside the SSPS and is a ‘control’ grade signal.

Question 16

What causes a turbine runback?

Answer 16

C3
C4
Loss of a circ water pump when P > 80%
Others…

Question 17

What signals cause a SIS?

Answer 17

Low PZR P
Low steamline P
High containment P

Question 18

What trips AMSAC?

What does it do?

Answer 18

2/2 Pimp > 40%
3/4 < 5% in 1/4 SG
Trips turbine and starts AFW (MDs and TD)

Question 19

What interlocks are associated with the SD system? (Cs and Ps)

Answer 19

C7: Arms SDs following load rejection that exceeds 5%/min
C9: Blocks SDs if condenser not available
P4: shifts Tavg mode from load reject to plant trip
P12: closes SDs to prevent uncontrolled cooldown

Question 20

List all trips (no flow or volt trips)

Answer 20

SR high flux. >10E5
IR, > 25%
PR low, >25%
PR high, > 109%
PR rate
OTDT
OPDT
PZR low P
PZR high P
PZR high level
SG lo-lo level
Turbine trip
SIS

Question 21

What happens on SG lo-lo level?

Answer 21

Reactor trip -> turbine trip
FWIS
AFW

Question 22

P14

Answer 22

SG level > 78%
Turbine trip -> reactor trip (if > P9)
FWIS
Trip MFP
Start AFW

Question 23

What is P9 and why is it set at that value?

Answer 23

A turbine trip will cause a reactor trip when 2/4 PR > 50%.

50% is used since the SDs (40%) and rods (10%) can handle a loss of load up to 50%.

Question 24

P10

Answer 24

2 PR > 10%
Permits block of IR trip and C1
Permits block of PR low trip
De-energizes SR
Feeds P7

Question 25

P4

Answer 25

Caused by reactor trip
Trips turbine
Switches SD mode
Feeds low Tavg (FWIS)