The role of I

1
The role of IC systems in power uprating
projects

• Presented by dr. Janos Eiler
• Portoroz, April 16, 2008

2
Contents

• Power uprating bases
• Power uprating and IC
• IAEA TECDOC on power uprating
• Power uprating in the Paks NPP
• Modernization of the Verona in-core monitoring
  system
• Next phases and future activities

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Why to uprate?

• Market changes induce the claim to operate the
  plants in an ever increasing efficiency.
• Efficiency can be increased either by a better
  utilization of existing capacities or by
  increasing the capacities.
• The utilities are aiming for additional
  production through the better utilization of
  available assets.
• Gaining public acceptance to increasing existing
  nuclear power plant capacity is significantly
  easier than that to constructing a new NPP.

4
Conditions enabling power uprating

• The average age of the nuclear units operating
  for the time being is above 23 years.
• The units were designed in the mid-seventies.
• Today, there is a more accurate knowledge on the
  behavior of structural materials and integrated
  effects of external and internal factors exerted
  on the components.
• Today demands affecting components during
  transients can be defined more exactly,
  uncertainties of calculations can be reduced,
  and, as a result, the conservatism applied in the
  original design can be reduced.
• Today more accurate and reliable control and
  assessment methods are available (accuracy of
  measurements, reduction of detection thresholds,
  etc)
• Knowledge related to nuclear fuel and core
  thermal hydraulics also had a considerable
  development. Fuel utilization arose to one and a
  half times of that in the eighties.

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Definition of power uprate

• The process of increasing the maximum licensed
  power level at which a commercial nuclear power
  plant may operate is called a power uprate.
  (Definition from the U.S. NRC)
• Types of power uprates
• measurement uncertainty recapture power uprates
• stretch power uprates
• extended power uprates

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Basic ways of power uprating

• Reducing uncertainty
• Improving efficiency
• Increasing thermal power

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Measurement uncertainty recapture uprates

• The reactor thermal power is validated by the
  nuclear steam supply system energy balance
  calculation.
• The reliability of this calculation depends
  primarily on the accuracy of feedwater flow,
  temperature, and pressure measurements.
• Because the measuring instruments have
  measurement uncertainties, margins are included
  to ensure the reactor core thermal power does not
  exceed safe operating levels.
• 10 CFR, Part 50, Appendix K (1973), required
  licensees to assume a 2.0 percent measurement
  uncertainty for the reactor thermal power.
• The current rule (2000) allows licensees to
  justify a smaller margin for power measurement
  uncertainty when more accurate instrumentation is
  used to calculate the reactor thermal power.

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Measurement uncertainty recapture uprates 2.

• Measurement uncertainty recapture (MUR) power
  uprates are those which seek to take advantage of
  more accurate measurement of the reactor thermal
  power in order to operate closer to, but still
  within, the analyzed maximum power level. They
  are achieved by implementing enhanced techniques,
  such as the improved performance of plant
  equipment both on the primary and secondary side,
  protection and monitoring system, operator
  performance, etc. These uprates are less than 2
  measured in electrical output power.
• The use of state-of-the-art feedwater flow
  measurement devices that reduce the degree of
  uncertainty associated with feedwater flow
  measurement can be an example.

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Measurement uncertainty recapture example
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Stretch power uprates

• Uprates are typically up to 7-percent and are
  within the design capacity of the plant. The
  actual value for percentage increase in power a
  plant can achieve and stay within the stretch
  power uprate category is plant-specific and
  depends on the operating margins included in the
  design of a particular plant.
• Stretch power uprates usually involve changes to
  instrumentation setpoints, but do not involve
  major plant modifications. This is especially
  true for boiling-water reactor (BWR) plants.
• In some limited cases where plant equipment was
  operated near capacity prior to the power uprate,
  more substantial changes may be required.

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Extended power uprates

• Extended power uprates are greater than stretch
  power uprates and are usually limited by critical
  reactor components such as the reactor vessel,
  pressurizer, primary heat transport systems,
  piping etc., or secondary components such as the
  turbine or main generator. To cope with these
  limitations, extended uprates usually require
  significant modifications to major
  balance-of-plant equipment such as the
  high-pressure turbines, condensate pumps and
  motors, main generators, and/or transformers.
  Extended power uprates have been approved for
  increases as high as 20 percent.

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Power uprate examples

• Many of the operating nuclear power plants in the
  world have already completed or are in the
  process of power uprating
• Loviisa Finland
• Paks Hungary
• Doel, Tihange Belgium
• Philippsburg, Emsland, Isar, and
  Unterweser Germany
• Gösgen, Mühleberg, Leibstadt Switzerland
• 7 out of 8 BWRs, and a PWR Sweden
• Kori, Yongwang Korea
• 105 power uprates as of July 2005 USA

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Current status of power uprates (examples)

• United States As of February 2004, NRC-approved
  power uprates of 12,500 MWt of capacity in 101
  cases. Planned power uprates in 31 operating
  units. About 6288 Megawatts thermal (MWt) or
  approximately 2068 Megawatts electric (MWe) power
  uprating by 2008.
• Spain Since 1990, capacity increase from power
  uprates is 609 MW (6,4).
• Sweden Between 1989 and 2003 the capacity of the
  nuclear power plants rose by 1183 MW.
• Finland The power of Olkiluoto has been raised
  in two stages (in 1984 and 1998) altogether by
  27. In the Loviisa plant the program completed
  in 1998. The two VVER440 units are operating at
  510 MW power level (9,1).
• Belgium The Tihange 1 Unit has carried out a
  power uprating of 8 .
• Hungary The Paks VVER-440 units are now operated
  at 465 to 500 MWe power and future increases are
  foreseen.

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Power uprates and IC

• Needed modifications in the instrumentation and
  control systems in relation to power upratings
  are not necessarily very substantial. The
  following preconditions must be fulfilled in the
  frame of IC
• Sufficient measurement ranges
• Sufficient accuracy of process parameter
  measurements
• Sufficient calculation algorithms to indicate
  credible reactor thermal power
• Sufficient possibilities for the adaptation of
  new limit values in the Reactor Protection
  System, limitation systems and control systems

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Typical examples of IC changes

• Inclusion of additional process sensors
• Replacement of sensors by ones with improved
  accuracy
• Modification of specific control systems to
  enable operation under different conditions.
• Development of more sophisticated calculation
  algorithms
• Optimised calculation of the measurement
  uncertainties permitting a reduction in the
  margin applied to the measurement of reactor
  thermal power.
• Modification of the reactor protection system
  setpoints
• Changes in the appropriate HSIs to accurately
  assess the current state of the plant
• Changes in alarm setpoints
• Changes in the instrument calibration procedures
• Adjustment of the plant computer and safety
  parameter display system

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IAEA TECDOC onThe Role of IC Systemsin Power
Uprating Projectsin NPPs
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IAEA TECDOC
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TECDOC contents

• Introduction to power uprating
• Limits, margins and their relevance to IC
• Calculation of thermal power
• Impact of power uprating on plant IC
• Human and training aspects
• Regulatory aspects
• IC implementation guidelines for power uprating
• IC benefits and lessons learned from power
  uprating
• Key recommendations
• References
• Glossary
• Country reports

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IC benefits and lessons learned

• Benefits
• Any modernization project, including a power
  uprating project, provides a good opportunity to
  improve areas where the IC design is judged to
  be deficient against modern standards or where
  the equipment is becoming obsolescent or
  unreliable.
• Concerns
• INPO reported that More than 40 events have
  occurred over the past five years as a result of
  inadequate analysis, design, or implementation of
  plant power uprates.
• Some units have operated beyond their licensed
  power levels for extended periods because of
  errors in reactor thermal power calculations
  following uprates
• Specific issues with the use of ultrasonic
  flowmeters

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Key recommendations

• It is important to fully understand the safety
  and technical bases for the claimed margins and
  limits.
• It is important to fully evaluate the areas of
  potential measurement uncertainty.
• Power uprates could potentially lead to various
  unwanted effects. It may be necessary to add new
  instrumentation to ensure that the operating
  conditions at the higher power level are
  adequately monitored and controlled.
• A power uprating could provide the opportunity
  for a wider modernisation of the plant IC
  systems.
• A comprehensive analysis should be undertaken
  covering all aspects of plant behaviour in all
  operational modes to provide input for the
  modified IC design.
• It is important to consider the changed (possibly
  more severe) operating conditions for IC
  equipment, qualification, etc.

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Key recommendations (contd)

• Particular attention should be paid to the design
  of the HSI modifications (if any), and of
  integration of this with the existing HSI, to
  ensure that operating staff performance is
  enhanced rather than degraded.
• In terms of the licensing application for a power
  uprate project, it should be noted that the
  Regulatory Authority will require the licensing
  submission to positively demonstrate that the
  existing safety level has been maintained or
  preferably increased, including all the IC
  aspects and consequences of it.
• Experience feedback from past power uprate
  projects has shown that some plants have incurred
  serious problems with their implementation (e.g.
  inadvertent violation of licensed power limits),
  due to instrumentation issues. Lessons learned
  from other PU projects should be considered.

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Power Uprating in the Paks NPP
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Early activities (uprate from 440 to 465 MW)

• High Pressure Turbine
• Blades of all stages of the High Pressure Rotor
  the 1st stage excepted were exchanged.
• From the diaphragms in the HP housing, stages No.
  5 and 6 were exchanged. As for the diaphragms of
  stages No. 2, 3 and 4, only the projections above
  the bandage were replaced.
• Final (end) - and diaphragm sealing were
  exchanged from flat springs to spiral ones.
• Low Pressure Turbine 
• Blades of rotor stages No. 1, 2, 3 and 4 were
  exchanged.
• From diaphragms of LP housing, those of stages
  No. 1, 2, 3 and 4 were exchanged.
• Having the steam separator exchanged, steam
  intake of the LP housing was modernized.
• Final (end) - and diaphragm sealing were
  exchanged from flat springs to spiral ones.

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The replacement of the turbine rotor
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Modifications for the new, 8 power uprating

• New fuel
• Primary circuit
• Secondary circuit
• Electrical systems
• IC systems
• Improvement of the primary circuit pressure
  control
• Implementation of a new in-core monitoring system
  and new reactor-physics calculations
• Modification of Reactor Protection System
  setpoints
• Modification of set values of control and
  protection systems and interlocks
• No feedwater flow measurement problems

26
Feedwater flow measurement orifice
27
The specific modifications
28
The specific modifications (contd)
29
The new encased bus bar for Units 1 and 2
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The new encased bus bar for Units 1 and 2
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Implementation of power uprating in Paks

• The first modified fuel was loaded in 2005 in
  Unit 4 (one third of the core). In 2006, when the
  Unit 4 reactor contained two loads of the
  modified fuel, the 108 power was possible to be
  attained.
• The stepwise increase of power, however, required
  a test run at about 104 for several months
  thus, the further increase up to 108 took about
  four months from the unit restart, and was
  reached on 28 September, 2006.
• All the necessary modifications were completed in
  Unit 1 in 2007, and after the stepwise increase
  of power, this unit also runs at 108 presently.
• As for Units 2-3, operation with fuel assemblies
  that are suspected to contain deposits will be
  terminated in 2008. This will provide the
  possibility for Unit 2 to reach 108 of power
  with clean fuel in 2008. Unit 3 will reach 104
  now, as further turbine modifications will need
  to be conducted in 2009.

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Main parameter changes after power uprating
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Primary circuit pressure control improvement
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Physical parameters limiting thermal power

• Maximum allowable temperature at the core
  sub-channel outlets 325 oC
• Corresponding primary circuit pressure 120,57
  bar

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The saturation temperature and pressure
bar
0C
36
The saturation temperature and pressure
bar
0C
37
The saturation temperature and pressure
bar
Real operating temperature
0C
The operating pressure must be maintained at a
stable 123.0 bar (abs) with an accuracy of /-
0.25 bar.
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Modernization of the VERONA In-Core Monitoring
System
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The old Hindukus in-core monitoring system
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The original system architecture
Nuclear Safety Dpt.
Unit Supervisor
Reactor Operator
Reactor Physicists
Computer Room
Bridge
MICROVAX 3100
MICROVAX 3100
Double Ethernet Network
Core noise diag-nostic output
PDA 1 Data Acquisitor
PDA 5
PDA 2
PDA 4
PDA 3
Signal Processing
To Diagnostic
Same as PDA 1
Sameas PDA 1
Same as PDA 1
Same as PDA 1
PAI
ADC
DIC
M68000VMEmachine
Lab
Data Acquisition
294 TP
288 PAIC
84 BU
359 GLV
SENSORS, TRANSMITTERS, PROCESS SIGNALS
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PDA Data acquisition cabinets
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Data acquisition cabinets
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Reactor in-core diagnostic cabinet
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The old MicroVAX servers
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System functions

• Process data acquisition
• Primary data processing
• Core calculations, limit processing
• Event processing
• Display functions, about 30 different mimics
• 3 types of archives, archive processing
• Logging
• On-line and archive trending
• Full scope archive playback
• Remote information services

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Core calculations

• Synchronous tasks
• Temperature calculation
• Calculation of loop and reactor heat balance
• Determination of core heat distribution (2D
  extrapolation)
• Asynchronous tasks
• Determination of linear power distribution (3D
  extrapolation),
• Hot-spot monitoring
• Data accumulation (assembly burn-out, etc.)
• New core models e.g. new power limitation
  regulations
• Limit violation check and alarm generation
• Periodic and change-sensitive archives

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Typical display presentation 1.
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Typical display presentation 2.
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Typical display presentation 3.
50
Typical display presentation 4.
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Main reasons for the upgrade

• Plant power uprating project
• 108 can be achieved only by using new fuel
  (3,82 radially profiled, 12.3 mm lattice pitch)
• On-line core analysis a more detailed modeling
  and higher accuracy is required
• Reduction of the current saturation temperature
  uncertainty margin
• Plant life time extension program
• Plant systems will run far beyond 2012 ? accurate
  and reliable monitoring systems are required

52
The saturation temperature and pressure
bar
Real operating temperature
0C
53
The saturation temperature and pressure
bar
Real operating temperature
0C
54
New system architecture

• Extension of the PDA hardware (2 CPUs / rack)
• Distributed system configuration Two new, 32
  bit, dedicated servers for data processing and
  for core analysis
• Windows based RPH servers ? (40x CPU speed)
• Windows based VDP servers
• 100 Mbps Fast-Ethernet network
• SCADA-based operator workstations
• Migration porting from OpenVMS to Windows
• Modernization of software tools
• Database archive management SQL standard
• Data visualization industrial (SCADA) tool
• Remote displays HTML / Java (browser only)
• Reliable system supervision resource allocation
• Open architecture, easy system expansion
• Graphic tools for system operation maintenance

55
The original system architecture
Nuclear Safety Dpt.
Unit Supervisor
Reactor Operator
Reactor Physicists
Computer Room
Bridge
MICROVAX 3100
MICROVAX 3100
Double Ethernet Network
Core noise diag-nostic output
PDA 1 Data Acquisitor
PDA 5
PDA 2
PDA 4
PDA 3
Signal Processing
To Diagnostic
Same as PDA 1
Sameas PDA 1
Same as PDA 1
Same as PDA 1
PAI
ADC
DIC
M68000VMEmachine
Lab
Data Acquisition
294 TP
288 PAIC
84 BU
359 GLV
SENSORS, TRANSMITTERS, PROCESS SIGNALS
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The new system architecture
Nuclear Safety Dpt.
Unit Supervisor
Reactor Operator
Reactor Physicists
Computer Room
Control Rod Position Meter
Firewall
Process Computer
RHP server PC Windows 2000
VDP server PC Windows 2000
VDP server PC Windows 2000
RHP server PC Windows 2000
Reactor Protection System Gateway
Double Fast-Ethernet Network
Core noise diag-nostic output
PDA 1 Data Acquisitor
PDA 5
PDA 2
PDA 4
PDA 3
Signal Processing
To Diagnostic
Same as PDA 1
Sameas PDA 1
Same as PDA 1
Same as PDA 1
PAI
ADC
DIC
Lab
Data Acquisition
294 TP
288 PAIC
84 BU
359 GLV
SENSORS, TRANSMITTERS, PROCESS SIGNALS
Two-proc. Motorola PowerPCVMEmachine
57
The new in-core monitoring system
58
Typical display presentation 1.
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Typical display presentation 2.
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Typical display presentation 2.
61
Typical display presentation 4.
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Modification of RPS set point values

• Keep the number of altered setpoints at a minimum
• All the ECCS signals and interlocks will remain
  unchanged
• Only three reactor shutdown signal setpoints need
  to be altered
• The turbine trip related signal (EP108)
• The limitation signals for neutron flux increase
  (EP114, EP115, and EP309),
• The reactor power limitation signal that embeds
  the number of running reactor coolant pumps too
  (EP302.a).

63
Next phases and future activities
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Next phases and future activities

• Internal radiation monitoring system (SEJVAL)
  replacement (tentative deadline 2010)
• Further realization of IC instrument replacement
• Facilitating the companys strategic tasks
• power uprating
• plant life time and aging management
• Entire replacement of the Plant Control Center
• Establishment and start of the remaining IC
  modernization

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The plant control center
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Preparation for the remaining IC modernization
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Old relay logic cabinets
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The main goals and tasks of the preparation

• The goals are to justify
• the necessity,
• the feasibility, and
• the economic suitability of the modernization,
  considering the planned license renewal of the
  plant
• Main tasks
• Literature research
• Elaboration of a formal methodology to describe
  the plant IC systems
• Development of the plant IC system database
• Identification of an optimized scope for the
  modernization
• Elaboration of the idealized system structure
• Equipment selection

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Most recent activities

• An IC expert group (composed of lead Hungarian
  professionals) published their statement on the
  necessity of the modernization (January 29,
  2007)
• Modernization in one large step per unit
• Immediate start of the project
• A long-term IC modernization strategy was
  published on September 6, 2007. The company
  management accepted the strategy.
• Review of functional adequacy of the existing
  systems
• Review of existing system structures
• Replacement of obsolete instrumentation
• Addition of missing functions
• Control room replacement
• Consistent physical separation
• The feasibility study has been completed
• The formal functional specification tool and an
  adequate simulation tool must be selected

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The functional architecture
71
Subsystems in the future, plant-wide IC
72
Functional model of the planned IC system
73
IC system functions

• F1 Safety functions
• F2 Process protection functions, interlocks
• F3 Automatic controls (functional group control,
  sequential control)
• F4 Manual remote control (through the MCR, ECR,
  or process computer)
• F5 Automatic closed-loop control
• F6 Information (Control room and process
  computer information presentation)
• F7 Diagnostic functions (Process diagnostics and
  IC self-diagnostics)

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Experiences and developments

• Safety IC system modernization project
• The number of process parameters to be measured
  will not change to a large extent
• The type and number of process sensors may change
  significantly
• The number of outputs and the type of actuation
  devices including their electrical power supply
  will not change dramatically
• The functions of the existing IC systems must be
  revised thoroughly
• Primary circuit pressure controller modernization
• The use of intelligent field devices and field
  buses is possible now
• The functional design of a pilot system (the
  reactor make-up water system) has been completed
• The number of process sensors in the existing
  system is 250
• The number of process sensors in the pilot system
  is 150

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The feasibility study cost estimates

• Based on Paks cost-benefit calculations, if the
  license renewal is successful and the plant
  lifetime is extended to 50 years, the economic
  gain is very significant

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Thank you for your attention!

• Any questions?