Actual Interest and Status of Reactor Instrumentation OnLine Monitoring at Cernavoda NPP

1
Actual Interest and Status of Reactor
Instrumentation On-Line Monitoring at Cernavoda
NPP

• Dragos Popa-NemoiuProcess Computers Branch, NPP
  CernavodaStr.Medgidiei nr.1, 905200 Cernavoda,
  Constanta, ROMANIAdpopa_at_cne.ro

On-Line Condition Monitoring of Equipment and
Processes in Nuclear Power Plants Using Advanced
Diagnostic Systems June
27-30, 2005 Knoxville Tennessee USA
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Introduction

• Cernavoda NPP is a CANDU 600 reactor, PHWR type,
  exported by AECL Canadian designer in ROMANIA
• The plant is in commercial operation from
  December 1997 after a long construction period
  which made many equipments obsolete
• This fact generated actual efforts for
  modernization.
• On-Line Monitoring Methods ( signal validation)
  are not yet systematically used at Cernavoda NPP
  but preparations for introducing these methods
  have started.

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Introduction (2)

• This presentation is an overview of the
  implementations intents based on local experience
  and available data acquisition systems
• There are also exposed expectations of plant
  personnel from On-Line Monitoring (OLM) promises.
• Organization reluctance in front of new
  technologies may be defeated only by well
  organized and coordinated efforts of the
  technology groups inside/outside the
  organization to reveal the benefits and gain
  confidence by pilot projects
• In Cernavoda NPP one of these technology groups
  is Control Computers Group, a technical group
  responsible for software based automation systems
  from plant.

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Introduction (3)

• Control Computers Group has taken the role of
  promoting internally these methods based on
  previous achievements of the group
• Plant scale data acquisition systems
• Successful introduction of IT based process data
  analysis methods in all plant departments
• Large experience with control software
  development

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Data acquisition developments

• In-house development of a Process LAN Plant
  Information System
• 2 approaches
• Control Computers Data using Gateways
• 2 DAQ systems for Shutdown Systems 1 2
• Use of COTS PC LAN technologies
• Continuous update of hardware software
• Cybersecurity Threats

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Data acquisition developments (2)

• Results
• On-Line Process variables trending facilities
  became available for Responsible Systems
  Engineers, the qualified personnel in charge with
  various plant systems surveillance
• Using from the beginning WEB based technologies
  and process LAN, the system became very popular
• Successful of timely regulatory requested
  transient analysis
• OSART Mission recorded large scale use of the
  Plant Information by all plant personnel as Good
  Practice Note

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Data acquisition developments (3)

• Plant management approved the development of
  several on-line systems and technologies.
• Unit 2 under construction requested deployment of
  the system for commissioning work reduction
• Became evident that Historical Data needs be
  preserved for any post-event and long term
  behaviors of systems analyses
• Deployment of the PLATON web server
• (PLAnt data Tailored informatiON) is the GUI of
  the various plant users

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Data acquisition developments (4)

• The PLATON web server allows station-wide access
  for real-time and historical parameters
  monitoring and are used by a total 400 users for
  (daily by 50 - 100 users)
• Trending visualization,
• Historical archives data retrieval,
• Plant status
• System health and performance monitoring,
• Work management,
• Training .
• 7000 parameters ( 3190 analog parameters ) are
  available at 4-sec time sampling from plant
  computers and 2180 parameters at 0.1 sec from
  the 2 DAQ systems .

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Data acquisition developments (5)
Friendly and customized user interfaces of PLATON
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Data acquisition developments (6)

• -Project Design was done by computer staff.
• Software in-house development was performed under
  Control Computers Quality Management available
  procedures.
• Few components were externally ordered.
• - Different software technologies (OPC,
  DataSocket) and programming systems (Varian
  assembler, Delphi, DSC LabView, Java, ASP) were
  used.

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Data acquisition developments (7)
Plant needs dictate development

• Real time and Historical alarms visualization
• Mouse Click on any alarms open the Alarm Response
  Operating Manual
• Became necessary to qualify for Main Control Room
  as Operator Support

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Data acquisition developments (8)

• Example of Empirical Condition Monitoring
  BO2LCV305-306 Changeover

• Every RSE create retrievable data sets which
  can be shifted against time.
• Create normal or abnormal patterns of plant
  process, system or equipment behaviors
• A lot of such patterns reveal need of OLM

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Data acquisition developments (9)
Example of on-line module

• The calculus module use level in various D2O
  tanks to evaluate mass and eventual leaks
• The system give immediate information in Main
  Control Room

On-line calculus of D2O available and leak rate
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Data acquisition developments (10)
Another Example of Empirical Condition
Monitoring

• Operators from Main Control Room perform displays
  hardcopy
• Hardcopies are historical data revealing what
  operator focused in plant behavior
• During transients this is the fast way to
  initiate technical support

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• Available IT Technologies
• Implement OLM on the available Process LAN and
  Plant Information
• OLM will be requested from the beginning on-line
  and providing alarms generation
• OLM modules need be OPC and SQL compatible to
  access existing real time and historical data

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Calibration concerns

• The calibration of instruments many times raised
  concerns, especially in the special safety
  systems (Shut-Down Systems 1 and 2 and Emergency
  Core Cooling) but also in control computers.
• Principles of independence, diversity and
  redundancy of these systems incorporated in CANDU
  600 design lead to an increased number of
  transmitters and associated calibration problems.
  
• Because different systems are independent and has
  redundant sensors for the same process variable
  it is an ideal case for OLM when an appropriate
  daq system concentrates all signals.
• A lot of calibration work is performed
  periodically as part of the preventive
  maintenance programs. Calibration drift is
  usually found only in 15-20 of transmitters. It
  is also well known that demounting/mounting
  transmitters from the loop is the subject of
  human errors. Sometimes these periodic
  calibrations are not enough to avoid unexpected
  signal problems

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Calibration concerns (1)
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Calibration concerns (2)
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Initial considerations for starting an OLM -
sensor validation pilot project at Cernavoda NPP

• Most of the process parameters in a nuclear
  power plant are strongly or weakly power related.
  At Cernavoda NPP there are 2 additional
  challenges related with reactor power which
  oriented computer group to the study of OLM as
  power sensors validation method
• Romanian National Regulatory Board has licensed
  Cernavoda NPP to operate reactor thermal power
  bellow a maximum limit of 100.5 from Nominal
  Power.
• Romanian National Grid as part of European Grid
  requested at every plant to participate at
  primary frequency control. In terms of reactor
  control this imposes a power modulation in a
  small band of /-1 from Nominal Power.

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Candu 600 Power Measurements

• Rapid Flux Measurements
• (i) 3 ion chambers located at one side of the
  calandria, and used at low power levels (less
  than 15 FP) for bulk regulation.
• (ii) 14 pairs of in-core platinum detectors, one
  pair in each of the reactor's 14 power zones, and
  used at higher power levels, (above 5 FP), for
  bulk regulation and (above 15 FP) for flux tilt
  control.
• Slow Flux Tilt Measurements
• (iii) 102 in-core vanadium detectors. The signals
  from these detectors are processed at 2 minute
  intervals by the Flux Mapping Routine . Among its
  other functions, the Flux Mapping Routine
  computes 14 zone flux calibration factors that
  are provided to the Power Measurement and
  Calibration Routine for the purpose of dynamic
  spatial flux calibration.
• Thermal Power Measurements
• (iv) 24 resistance temperature devices (RTDs),
  distributed in the four pairs of reactor inlet
  and outlet headers, and used below 70 FP, for
  dynamic calibration of bulk power.
• (v) 4 sets of boiler power measurement devices,
  each set consisting of a steam flow meter, a
  feedwater flow meter, and a feedwater temperature
  detector. These are located on the secondary side
  of the four steam generators, and are used above
  50 FP for dynamic calibration of bulk power.

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Other identified use of OLM

• Plant Information system is used also in the
  Emergency Control Center (ECC) for coordination
  of station response in large accidents.
• Special application in ECC is Critical Safety
  Parameters Monitor. This is a symptom based
  system expected to be used during harsh
  conditions of site accident.
• The design of this system raised concerns about
  the sensor accuracy validation.
• Sensors connected at this system are associated
  with Plant Post-Accident Monitor system in Main
  Control Room, a bulk of earthquake and
  environmental qualified sensors

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Other identified use of OLM

• In ECC there are no means to verify accuracy of
  sensors as in Main Control Room where there are
  methods of validation which could be performed
  using alternative panel indications and Secondary
  Control Room sensors.
• For the time being OLM methods seems to be a
  candidate for sensors validation in ECC during
  accident.
• The models training will be done at zero power
  level, with special data sets, specific for
  accident conditions.

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Other identified use of OLM
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Conclusions

• The precursors of OLM techniques exist in the
  recent history of Plant Information system and
  these facts prepared the plant personnel for
  impact of new automated methods.
• The OLM pilot will focus on power measurement
  sensors and on the on-line alarming capabilities
  of the system.
• Used in parallel with conventional maintenance of
  instruments eventually could contribute to
  calibration reduction (pessimistic point of view
  but depend on success).

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Conclusions (2)

• The Plant Information system at Cernavoda NPP is
  a strategic investment and several developments
  are in progress.
• As soon as this system became fully qualified for
  operation use it will contribute to the evolving
  plant control center needs and will constitute
  the baseline for the development of new automated
  facilities.
• OLM signal validation is the best and immediate
  approach and not only for calibration reduction