RPS

Question 1

What is the purpose of the RPS?

Answer 1

To initiate a reactor trip to ensure that the Technical Specification Safety Limits are not exceeded.

Linear Heat Rate - < 21kw/ft

DNB > 1.17/1.154/1.141

PCS Pressure < 2750 psia

Question 2

What are the RPS Trips?

Answer 2

1. Reactor High Power
2. Reactor Power High Rate of Change
3. Primary Coolant System Flow
4. Steam Generator Level 1
5. Steam Generator Level 2
6. Steam Generator 1 Low Pressure
7. Steam Generator 2 Low Pressure
8. Pressurizer High Pressure
9. Thermal Margin/Low Pressure
10. Loss of Load
11. Containment High Pressure

Question 3

What are the RPS Power Supplies?

Answer 3

Channel A - Y10

Channel B - Y20

Channel C - Y30

Channel D - Y40

Question 4

What are the two types of RPS Trip Units?

Answer 4

Bistable Trip Units

• 7 of the RPS Trips are from Bistable Trip Units

Auxiliary Trip Units

• 4 of the RPS Trips are from Auxiliary Trip Units

Question 5

What is a Bistable Trip Unit?

Answer 5

Bistable Trip Unit

• The measured value is compared to a pre-determined or calculated set point
  
  • Measured value > set point
    
    • Bistable de-energizes

Question 6

What is an Auxiliary Trip Unit?

Answer 6

Auxiliary Trip Unit

• Digital Input
  
  • Voltage Present = safe
  • No Voltage Present = unsafe
    
    • Trips

Question 7

What are the RPS Bistable Unit Trips?

Answer 7

Can be identified on the RPS panel by the presence of potentiometer adjusting holes.

1. Primary coolant system low flow
2. Steam generator 1 low level
3. Steam generator 2 low level
4. Steam generator 1 low pressure
5. Steam generator 2 low pressure
6. Pressurizer high pressure
7. Thermal margin/low pressure

Question 8

What are the RPS Auxiliary Unit Trips?

Answer 8

Auxiliary Trip Units

1. Reactor high power (variable high power trip)
2. Reactor power high rate of change
3. Loss of load
4. Containment high pressure

Question 9

What makes up the coincendence logic matrix?

Power Supplies?

Trip Inputs?

Answer 9

Six logic matrices, or “logic ladders

• Each ladder compares output of 1 RPS unit to another

1. AB
2. AC
3. AD
4. BC
5. BD
6. CD

Ladders are thus supplied by two different preffered AC busses

11 trips per channel = 22 per ladder

Each ladder powers 4 matrix relays which de-energize with a conicendent trip.

Question 10

How does a logic ladder trip the reactor?

Answer 10

Clutch Power Supplies are fed by Y-30 and Y-40 through four large power “M” relays.

The M relays are controlled by four trip paths of six closed matrix relay contact pairs arranged in series (an OR arrangement).

If a coincedent trip occurs in a ladder, the associated M-relay opens and de-energizes both power supplies. Reactor is tripped.

Question 11

What supplies Clutch DC Power Bus 1, 2, 3 and 4?

Answer 11

Clutch DC Power Bus 1

• Supply 1 (Y-30 via trip paths 1 & 2)
• Supply 3 (Y-40 via trip paths 3 & 4)

Clutch DC Power Bus 2

• Supply 2 (Y-30 via trip paths 1 & 2)
• Supply 4 (Y-40 via trip paths 3 & 4)

Question 12

What is the M-Coil arc suppression?

Answer 12

When M relay contacts open, the magnetic field collapse in the coil induces a large voltage spike in the connected cables.

Could “weld” closed the matrix relay contacts.

Suppression network of capcitor/zehner diode shunts the spike.

Question 13

What is the normal/tripped reading on the M-coil suppression network?

Answer 13

Normally indicates about 20 VAC - 100 VAC is dropped across capacitor, 20 across resistor which is indicated on voltmeter for that M-coil.

If reactor tripped, should read 0 VAC.

Not 20 if reset or 0 if tripped, investigate to ensure matrix relay functionality.

Question 14

What are the K-relay power supplies?

Answer 14

K1 and K2 - DC Clutch Power Bus 1

K3 and K4 - DC Clutch Power Bus 2

Question 15

What is the function of the K-relays?

Answer 15

When de-energized, K-Relays function to:

1. CRDM Rundown - all but part-length
2. Trip Reset - prevents reactor from auto resetting and damaging CRDM gears
3. 30-Second Lockout - prevents manual reset for 30 seconds
4. Turbine Trip - energize 20/AST Relay
5. Reactor Trip signal to PPC/Datalogger
6. EK-0972, “REACTOR TRIP”

Question 16

What are the indications for Clutch Power supplies?

Answer 16

C-06, Channel A & D, bottom rack

Clutch power supplies are de-energized, i.e. after a reactor trip,

• “AC ON,” “AC TROUBLE,” “GROUND,” and “DC ON” lamps go dark
• “TRIP” lamp illuminates (red)

Question 17

How does the manual reactor trip button on C-02 function?

Answer 17

C-02 Trip Button

De-energizes all four M relays, which de-energizes the four clutch power supplies

Question 18

How does manual trip button 2 function?

Answer 18

Reactor Trip Button 2 on C-06

De-energizes the undervoltage coil on reactor trip breakers 42-1/RPS and 42-2/RPS, interrupting the voltage from Preferred AC Busses Y-30 and Y-40 to the clutch power supplies

Question 19

How do you clear a reactor protective trip signal?

Answer 19

Bypass

Clear by correcting the conditon

Question 20

How can you tell what has caused a trip?

Answer 20

Indicated by illuminated red lamps on the affected trip unit front panels, and by illuminated related annunciators.

Question 21

What are the Reactor Protective System Trip Bypasses?

Answer 21

Reactor Protective System Trip Bypasses

There are three means of bypass:

1. Trip Channel Bypass
2. Automatic Bypass

• Only on Loss of Load and High Rate of Power Change
  1. Zero Power Mode Bypass

Question 22

How and when do you apply a trip channel bypass?

Answer 22

Trip Channel Bypass

• Manually implemented via keyswitch directly above the trip unit to be bypassed.
  
  • Only 1 key for each trip; fits all four channels of that trip

Used:

• To prevent an inadvertent reactor trip when a trip unit is being serviced or calibrated
• To temporarily remove a trip unit from service when either it or its instrument channel is inoperable

Question 23

How is the coincendence logic impacted when a trip channel is bypassed?

Answer 23

In BYPASS, the trip logic changes from 2/4 to 2/3 channels

• Yellow light above keyswitch illiminates
  
  • If the supplying preferred AC buss is de-energize, no light

TS limit of 7 days for bypass

Question 24

How is Automatic Bypass accomplished?

Answer 24

Automatic Bypass

Only available on Loss of Load and High Rate of Power Change

Loss of Load

• Enabled >15% power
• Disabled < 15% power

High Rate of Power Change

• Disabled < 10^-4% power by one of two Source/Wide Range NIs
• Disabled > 15% power by power range NI
• Enabled between 10-⁴% power and 15% power

Question 25

What is the function of the Zero Power Mode (ZPM) Bypass?

Answer 25

Zero Power Mode (ZPM) Bypass * It is a manual bypass. * Used when reactor shutdow to bypass certain reactor trip signals to allow control rod withdrawel.

Question 26

What trips can be bypassed using the Zero Power Mode Bypass?

Answer 26

Trips bypassed via Zero Power Mode Bypass: * PCS Low Flow * SG 1 Low Pressure * SG 2 Low Pressure * Thermal Margin/Low Pressure

Question 27

How do you insert a Zero Power Mode Bypass?

Answer 27

Inserting Zero Power Mode Bypass * Manually inserted via 1 keyswitch for each RPS channel (four keyswitches total). * +15V is applied to the output of the four bypassed trip units, ensuring that the trip unit outputs cannot de-energize.

Question 28

How is Zero Power Mode Bypass automatically not allowed?

Answer 28

At \>10^-4% Power - ZPM Bypass is automatically removed. In series with the bypass keyswitch are automatic removal contacts (one for each trip unit) that are operated by the associated Source/Wide Range NIs * NI 1/3A removes the ZPM bypass from trip units in RPS Channels A & C * NI 2/4A removes the ZPM bypass from trip units in RPS Channels B & D

Question 29

How is the insertion/removal of a Zero Power Mode Bypass accomplished?

Answer 29

Lamp 1 on panel - availability of bypass * Dark when test push button depressed if bypass available * Illuminated when test push button depressed at \> 10^-4% power Lamp 2 on panel - insertion of bypass * Dark when test push button depressed if keyswitch in bypass * Illuminated when test push button depressed and no bypass Bottom-Line * Lights dark if bypass inserted/available * Lit if bypass not inserted/not available

Question 30

What are the requirements prior inserting a zero power mode bypass?

Answer 30

Ensure operable both Wide Range NIs Ensure power level less than 10-4% RTP Verify primary system boron concentration greater than Cold Shutdown concentration

Question 31

When testing removal of ZPM bypass, why is only 1 test pushbutton at a time depressed?

Answer 31

SOP-36 contains a Caution that states, “Zero Power Mode test buttons should be operated one at a time to prevent Reactor Protective System trips.”

Question 32

How do you place an RPS unit in trip?

Answer 32

Loosen both hold down screws on desired trip unit Pull RPS trip unit out at least two inches, using the handle on the front of the trip unit Ensure the connections on the back of the trip unit are disengaged Changes 2 out of 4 to 1 out of 3.

Question 33

How do you tell if and where a ground is within the logic matrix?

Answer 33

Two rows of four lights. If ground on positive side: * Top lights go dark, bottom lights get brighter If ground on negative side * Bottom lights go dark, to lights get brighter

Question 34

If a monitored parameter input signal fails high, how will trip unit react?

Answer 34

If trip unit designed to trip on high * Only that channel (A,B,C,D) trips * Logic becomes 1 out of 3, unless bypassed to become 2 of 3. If trip unit desinged to trip on low * That unit will not trip, but other three will.

Question 35

How will a failure of a Preferred AC Bus impact RPS?

Answer 35

All parts of the affected RPS Channel will de-energize: * Field Instrumentation * All eleven trip units * All three 28 VDC logic matrix power supplies( i.e. AB, AC, AD, etc) * If Y-30 fails, then clutch power supplies 1 and 2 will lose their power, causing a half-trip * If Y-40 fails, then clutch power supplies 3 and 4 will lose their power, causing a half-trip

Question 36

Why are the Red Matrix lamps replaced via work order?

Answer 36

due to the potential for a shorted bulb to trip both auctioneered 28VDC Matrix Ladder power supplies and cause a plant trip

Question 37

What supplies ATWAS Power?

Answer 37

ATWAS Power Y-230

Question 38

What are the ATWAS Solenoids?

Answer 38

ATWAS Solenoids If DC control power is lost, then two solenoids, SV-0522G and SV-0522H, de-energize and open the normal air or backup nitrogen supply line to the air-to-open steam supply valve CV-0522B, which provides steam to the steam-driven auxiliary feedwater pump.

Question 39

What is the ATWAS Setpoint?

Answer 39

ATWAS Setpoint 2 out of 4 on pressurizer pressure \> 2375 psia

Question 40

What is the function of ATWAS?

Answer 40

ATWAS Function * Trip the reactor * Initiate auxiliary feedwater * Trip the main turbine

Question 41

What are the 1 Hour or Less TS actions related to RPS?

Answer 41

One Hour or Less TS Actions One or more ZPM Bypass Removal channels inoperable * Immediately Remove the affected ZPM Bypasses. OR * Immediately Declare the affected trip units inoperable. One or more Functions with two RPS trip units or associated instrument channels inoperable. Not applicable to high SUR or Loss of Load * Within 1 hour, Place one trip unit in trip One channel of Trip Initiation Logic inoperable. * Within 1 hour, De-energize the affected clutch power supplies Two channels of Trip Initiation Logic affecting the same trip leg inoperable * Immediately De-energize the affected clutch power supplies.