ACADs (08-006) Covered

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Reactor Regulating System
ACADs (08-006) Covered Keywords Steam
bypass, transient overshoot, reactor coolant,
main turbine, nuclear instrumentation system,
pressurizer, level control system, CEDMCS,
Control Element Drive Motion Control System,
diagram, input signal processing, turbine load
index, excore control, lag network. Description
Supporting Material
1.1.1.9 1.1.4.6 1.1.9.1.2 1.3.8.2 2.1.15 5.4.1.2 5.4.1.8 5.4.3.9



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NID20
REACTOR REGULATING SYSTEM
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Pre-Job Brief

• Identify critical steps
• Identify error likely situations
• Identify the worst thing(s) that can happen
• Identify specific error prevention defenses to be
  used
• Identify actions to assure proper configuration
  control

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REACTOR REGULATING SYSTEM   COURSE TERMINAL
OBJECTIVE   Given the appropriate reference
material, the IC Technician will describe the
operation and maintenance of the Reactor
Regulating System. Mastery will be demonstrated
by passing a written examination with a score of
80 or better.
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Lesson Enabling Objectives

• EO01 Describe the method of reactor control
  programming used at PVNGS.
• EO02 State the purpose of the RRS.
• EO03 List the input signals for RRS and describe
  the source instrumentation for these signals.
• EO04 Given a block diagram of the RRS for
  reference, describe how the RRS uses signal
  inputs to develop CEA motion demand output
  signals.

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Lesson Enabling Objectives

• EO05 Describe the RRS outputs and the effect of
  these on other systems when RRS is placed in the
  test mode.
• EO06 Given the appropriate procedures, describe
  how the testing of RRS is accomplished
• EO07 Describe the use of Prevent Event Tools and
  Electrical Safe Work Practices to minimize human
  performance errors.
• EO08 Given examples of RRS maintenance problems,
  determine the fault using applicable RRS prints,
  Tech Manual, and Setpoint Document.

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• EO01 Describe the method of reactor control
  programming used at PVNGS.

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Temperature Control Programs
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Ops Info Manual
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TAVG is used to represent Reactor Power
100 RX Pwr
0 RX Pwr
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TLI is scaled and biased so it can be compared to
Tavg
100 Secondary Load
5.707
0 Secondary Load
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• EO02 State the purpose of the RRS.

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Reactor Regulating System Purpose

• The RRS, in conjunction with CEDMCS, forms a
  closed-loop control system which regulates RCS
  TAVG to a setpoint programmed as a function of
  turbine load (TLI) to satisfy 100 power Main
  Steam pressure requirements.
• The RRS provides speed and direction signals to
  CEDMCS to reposition regulating CEA's to maintain
  RCS TAVG within a deadband of programmed
  reference temperature (Tref).

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RRS Overview

• The Reactor Regulating System (RRS) is a
  non-safety related system.
• Located to the rear of control board B05 in
  cabinet J-SFN-C03R.
• Supplements operator manual control actions
  by
• Furnishing rapid response Automatic Control and
  Control Element Drive Mechanism Control
  Withdrawal Prohibit (AWP) signals to the System
  (CEDMCS).

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RRS Design

• The system is designed, in conjunction with SBCS,
  to control without significant transient
  overshoots, reactor power and turbine steam
  by-pass to counter or make adjustment for the
  following
• Load rejection of any magnitude.
• Up to 10 step change in NSSS load.
• Up to 5 per minute ramp change in NSSS load.

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• EO03 List the input signals for RRS and describe
  the source instrumentation for these signals.

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RRS INPUTS

• a) Reactor Coolant System (RC)
• Provides TH and TC signals from both loops to RRS
  used to calculate TAVG
• Supplies TC for AWP. An AWP is generated from any
  TC loop when temperature is gt 575oF.
• b) Main Turbine (MT)
• Provides 1st stage shell pressure signals to RRS
  used as indication of turbine power and TLI
  signal to RRS
• c) Nuclear Instrumentation System (SE)
• Provides signals to RRS from Control Channel
  Nuclear Instruments used in Power Error
  calculation.

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RRS INPUTS

• d) PLCS (SF)
• The system receives from the Pressurizer Level
  Control System a contact closure signal
  indicating that the setpoint program is in Local.
  
• e) CEDMCS (SF)
• The system receives from the Control Element
  Drive Motion Control System a contact closure
  signal indicating that the CEDMCS is in Auto
  -Sequential' mode (AS).
• Sheet 2 of 16

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• EO04 Given a block diagram of the RRS for
  reference, describe how the RRS uses signal
  inputs to develop CEA motion demand output
  signals.

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RRS Input Signal Processing

• TH There is one RTD (RCN-TT-111X and 121X)
  located in each hot leg that is used in
  determination of TAVG.
• The range of these RTDs is 500F to 650F.
• A recorder and meter for both RTDs is located on
  B04.
• TC There is one RTD (RCN-TT-111Y and 121Y)
  located in RCS Cold Leg loops 1A and 2B that is
  used in determination of TAVG.
• The range of these RTDs is 500F to 650F.
• A recorder and meter for both RTDs is located on
  B04.
• An Automatic Withdrawal Prohibit Signal (AWP)
  will be generated in the RRS and sent to CEDMCS
  if either loop TC is gt 575F.

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Turbine load index

• TLI is used by the RRS to develop the reference
  temperature for TAVG based on secondary load.
• Main Turbine first stage pressure (TFSP) is used
  to develop this signal because it is an
  approximate linear correlation to turbine load.
• MTN-PT-PT11A and 11B provide this input to RRS.
• There is not an indicator for these two pressure
  transmitters.
• An additional first stage pressure transmitter
  that DOES NOT input into the RRS (PT-10) provides
  input to the EHC system and can be read on B06.

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Calculation of TREF

• TLI is used to develop a reference temperature,
  TREF which is programmed from 0 to 100 TLI.
• TLI output to the TREF function generator is high
  limited to 100.
• An AMI will occur when selected to average TLI if
  there is gt 5 difference between TLI 1 and 2.

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Excore Control Channel

• There are 2 control channel inputs for reactor
  power.
• Either Rx power input or the average of the 2 may
  be used in RRS which is selectable on the RRS
  test panel.
• Each Rx power input is continuously compared to
  the other channel and an AMI is generated at a 5
  difference between channel inputs if the Rx power
  input is selected to average.

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Lag Network

• The lag network gives higher amplification to
  rapidly changing inputs than for slow changing
  inputs.
• This provides faster response to rapidly changing
  inputs than for slow changing inputs and adds
  stability to the temperature control loop.
• Its output is sent to Total Error.

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Total Error

• Total Error is generated by summing Power Error
  and Temperature Error.
• When TAVE is 3oF above TREF, a CEA insertion
  demand is generated to insert CEA's and lower
  TAVE.
• The insertion demand will reset at a Total Error
  of 2.84oF.
• Likewise, at a Total Error of -3oF, a CEA
  withdrawal demand is generated.
• This will reset at -2.84oF.

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TREF
Vout 3 X Ain (Tavg) 3 X Bin (Tref) 5
Out 5.773vdc
NC5vdc
Gain 0.188 Bias 4.273vdc
Gain 3 Bias 5.0vdc
Different values in different units
ET
Vout Vin X Gain Bias
Gain 0 Tau 0.1min
EB
ET
Vout 2.5 X (Ain) 2.5 X (Din 2) 7.5
NC2vdc
NC5vdc
Ain (ET) has Gain 2.5 Din (EB) has Gain 2.5
Bias(-)2vdc Vout has Bias (-7.5)
Gain 1.25 Bias 2vdc Tau 0.5 min
Values represent U3 conditions
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• EO05 Describe the RRS outputs and the effect of
  these on other systems when RRS is placed in the
  test mode.

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RRS outputs

• PLCS (SF)
• CEDMCS (SF)
• SBCS (SF)
• FWCS (SF)

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PLCS (SF)

• The system outputs to the Pressurizer Level
  Control System a 0 10V signal of TAVE used in
  the generation of programmed level from 0 to 100
  power.

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CEDMCS (SF)

• The system outputs to the Control Element Drive
  Motion Control System as contact closures the
  following
• CEA Withdrawal Demand
• CEA Insertion Demand
• CEA High Rate Movement Demand
• Tavg - Tref High Alarm (AWP - Automatic
  Withdrawal Prohibit)
• A High Input Deviation alarm (AMI - Automatic
  Motion Inhibit)
• A Reactor Coolant Cold Leg High Temperature alarm

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SBCS (SF)

• Uses TAVE from RRS in generation of Quick Open
  Block signal and Turbine Runback Demand signal to
  RPCB.
• Uses Reactor Power from RRS for low power (15)
  AMI generation
• Uses TLI for AMI permissive and AMI threshold
  determination
• CEA Automatic Withdrawal Demand is used to reset
  the AMI

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FWCS (SF)

• Receives TAVE signal from RRS used in generation
  of Refill Demand signal after a Rx trip.
• Receives Reactor Power Signal from RRS which is
  used for the low power (15) bistable -
  Economizer/Downcomer Swapover.

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TROUBLESHOOTING HINTS 1. Optimize the use of
the Test Panel. 2. Make certain that a solid
understanding of the specific modules is obtained
before troubleshooting. 3. Never overlook
switches and transfer stations. They are also
susceptible to failure. 4. Depress the "LIGHT
TEST" pushbutton on the Test Panel to ensure that
all the LEDs are operating properly. 5. Always
ensure that power is applied. 6. Never rule out
the possibility of loose wires or disconnected
cables. 7. Inspect for debris or tools within the
cabinet.