RPS Flashcards by Larry King

What is the purpose of the RPS?

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

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What are the RPS Trips?

Reactor High Power
Reactor Power High Rate of Change
Primary Coolant System Flow
Steam Generator Level 1
Steam Generator Level 2
Steam Generator 1 Low Pressure
Steam Generator 2 Low Pressure
Pressurizer High Pressure
Thermal Margin/Low Pressure
Loss of Load
Containment High Pressure

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What are the RPS Power Supplies?

Channel A - Y10

Channel B - Y20

Channel C - Y30

Channel D - Y40

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What are the two types of RPS Trip Units?

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

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What is a Bistable Trip Unit?

Bistable Trip Unit

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

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What is an Auxiliary Trip Unit?

Auxiliary Trip Unit

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

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What are the RPS Bistable Unit Trips?

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

Primary coolant system low flow
Steam generator 1 low level
Steam generator 2 low level
Steam generator 1 low pressure
Steam generator 2 low pressure
Pressurizer high pressure
Thermal margin/low pressure

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What are the RPS Auxiliary Unit Trips?

Auxiliary Trip Units

Reactor high power (variable high power trip)
Reactor power high rate of change
Loss of load
Containment high pressure

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What makes up the coincendence logic matrix?

Power Supplies?

Trip Inputs?

Six logic matrices, or “logic ladders

Each ladder compares output of 1 RPS unit to another

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.

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How does a logic ladder trip the reactor?

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.

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

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)

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What is the M-Coil arc suppression?

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.

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

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.

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What are the K-relay power supplies?

K1 and K2 - DC Clutch Power Bus 1

K3 and K4 - DC Clutch Power Bus 2

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What is the function of the K-relays?

When de-energized, K-Relays function to:

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

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What are the indications for Clutch Power supplies?

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)

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

C-02 Trip Button

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

How does manual trip button 2 function?

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

How do you clear a reactor protective trip signal?

Bypass

Clear by correcting the conditon

How can you tell what has caused a trip?

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

What are the Reactor Protective System Trip Bypasses?

Reactor Protective System Trip Bypasses

There are three means of bypass:

Trip Channel Bypass
Automatic Bypass

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

How and when do you apply a trip channel bypass?

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

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

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

How is Automatic Bypass accomplished?

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

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

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.

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

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

How do you insert a Zero Power Mode Bypass?

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.

How is Zero Power Mode Bypass automatically not allowed?

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

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

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

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

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

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

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.”

How do you place an RPS unit in trip?

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.

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

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

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

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.

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

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

Why are the Red Matrix lamps replaced via work order?

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

What supplies ATWAS Power?

ATWAS Power Y-230

What are the ATWAS Solenoids?

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.

What is the ATWAS Setpoint?

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

What is the function of ATWAS?

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

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

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.