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LOIT Systems 2018 > RPCB: Reactor Power Cutback > Flashcards

RPCB: Reactor Power Cutback Flashcards

1
Q

If the TEST/RESET button is depressed (backlit) and a RPCB occurs, what will happen?

A

Nothing. TEST/RESET inhibits all RPCB functionality.

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2
Q

What is a Large Load Reject?

A

A signal sent to RPCB sent from SBCS. SBCS compares steam flow and TLI to PZR Pressure (specifically if TLI goes down with Ppzr going up). Need both channels to sense a load change to get a LLR.

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3
Q

What happens if a selected subgroup is on the Hold Bus on a RPCB?

A

That subgroup will not fall into the core. CPCs will then trip the reactor for CEAs being out of sequence because it expected those CEAs to drop.

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4
Q

What happens to the CEAs after the RPCB signal clears?

A

Rods are then able to be controlled by the RRS and/or manual operator control.

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5
Q

What would happen if a Large Load Reject were initiated on a LOFP RPCB?

A

The Quick Open Block for SBCS would not work.

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6
Q

When would a Turbine Setback signal clear?

A

When the Load Limit Potentiometer is dialed below 60% (Load Limit light comes on)

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7
Q

What does the AUTO ACTUATE OOS button do in the RPCB System?

A

Defeats automatic only RPCB operation.

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8
Q

When a Cutback is generated for a lost Main Feed Pump, what signal is sent to SBCS? Why?

A

Quick Open Block

QO is for a Main Turbine Trip. A MFP is lost, not the turbine. We’d couple a significant reduction in feed with a large increase in steam demand.

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9
Q

How do you perform a manual RPCB?

A

Push the DROP SUBGRP button concurrently with the LOFP button or the LLR button on B05.

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10
Q

What two events will result in a RPCB?

A
  • Loss of a Main Feed Pump

- Large Load Reject (LLR)

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11
Q

What happens if RRS Tave fails low on a Main Feed Pump trip?

A

CEAs drop due to RPCB and you’d get a continuous Main Turbine Runback

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12
Q

What needs to work correctly to keep from tripping the Reactor on a Turbine Trip?

A

RPCB
SBCS
Fast Bus Transfer

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13
Q

How long is a RPCB signal present?

A

10 Seconds

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14
Q

How do you reset a RPCB?

A

Press the AUTO ACTUATE OOS and TEST/RESET buttons. Then dial the Load Limit Potentiometer counter clockwise until the Load Limit light illuminates.

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15
Q

What signals are sent to the EHC System on a RPCB?

A

Setback
Runback
Increase Inhibit

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16
Q

What is the purpose in the ARM signal sent to CEDMCS on a Cutback?

A

Prevents CEA re-latch before hitting the bottom of the core.

17
Q

Which signal sent to CEDMCS actually opens the circuit to the CEA coils?

A

DROP

18
Q

To de-select the CEAs for RPCB and leave RPCB in service, what buttons need to be pressed?

A

AUTO ACTUATE OOS and TEST/RESET both, twice.

19
Q

What specific parameter on a Main Feed Pump will initiate a RPCB when you lose it?

A

Main Feed Pump oil pressure <75 psig from both of 2 pressure switches (2/2 logic)

20
Q

What happens on a Turbine Setback?

A

MT Control Valves go to 60% at 480%/minute

21
Q

When is a Main Turbine Runback signal get generated?

A

When both ARM and DROP signals are present concurrent with:

  • TLI > 60% OR
  • sum of PT-1024 and Tave are low.
22
Q

What happens to the RPCB System if NNN-D11 is lost?

A

RPCB is totally disabled (no CEAs or turbine actions)

23
Q

To initiate a RPCB on a loss of a Main Feed Pump, what additional parameter must be met?

A

Reactor Power > 74%

24
Q

What happens to the RPCB System if NNN-D12 is lost?

A

Turbine Runback is disabled.
- On a cutback, the Main Turbine will only setback to 60% which will result in a Reactor Trip due to Secondary Power > Primary Power

25
Q

Where does the signal for a Main Turbine Runback get generated?

A

From SBCS

26
Q

What (if anything) happens to Turbine Runback capability when SBCS is placed in TEST or disconnected?

A

Main Turbine Runback is blocked

27
Q

What happens if PT-1024 fails low on a Main Feed Pump trip?

A

CEAs drop due to RPCB and you’d get a continuous Main Turbine Runback

28
Q

What is a RPCB Flag?

A

Its a signal generated by the CPCs that says its ok if a flagged CEA drops into the core because its associated with a RPCB.

29
Q

What is Turbine Increase Inhibit and when does it occur?

A
  • Prevents the INCREASE LOAD button from raising Main Turbine Load until the RPCB is manually reset.
  • Occurs on any RPCB
30
Q

How fast a Main Turbine Setback?

A

Moves the Main Turbine at 480%/min to 60%

31
Q

If the Main Turbine is in Standby, what features of the RPCB system pertaining to the Main Turbine don’t work?

A

Setback
Runback
Increase Inhibit

32
Q

When does a Turbine Setback occur?

A

When both ARM and DROP (1 and 2) signals exist.

33
Q

What two signals are sent to CEDMCS to drop rods for a Cutback? How long?

A

ARM and DROP

10 seconds

34
Q

What criteria must be met to get a RPCB for a Loss of a Main Feed Pump?

A

Two switches on one Main Feed Pump must read < 75psig control oil pressure

35
Q

How fast is a Main Turbine Runback?

A

Lowers load reference 130%/min due to Load Set Motor limitations.

36
Q

What does the TEST/RESET button do in the RPCB System?

A

It removes ALL auto and manual RPCB capability from service. Also deselects any selected CEAs.

LOIT Systems 2018 (33 decks)

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