Monitoring System for Accuracy and Reliability Characteristics of Design Temperature Measurements in

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Monitoring System for Accuracy and
Reliability Characteristics of Design Temperature
Measurements in PWR/VVER-440 Reactors
Dr. Stanislav tanc Mário Repa Martin Slanina
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Slovakia
Official language Slovak Capital city
Bratislava (population 428 672) Neighbouring
countries Czech Republic, Poland, Ukraine,
Hungary, Austria Area 49 035 km2 Population 5
379 455 (51.4 women) Population density
109/km2
Membership of international organisations EU,
NATO UN, UNESCO, OECD, OBSE, CERN, WHO, INTERPOL
etc.
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VUJE, a.s.

• Establishment
• 1977 as the Nuclear Power Plant Research
  Institute
• Number of employees 600
• Scope of work
• engineering
• projecting
• research
• (de)commissioning

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Nuclear Power Plants in Slovakia

• Bohunice NPP
• - V1 2 Units type VVER-440/V-230
• V2 2 Units type VVER-440/ V-213
• - A1 in decommissioning
• Mochovce NPP
• 2 Units type VVER-440/ V-213
• - 2 Units type VVER-440/V-213 in finishing

Total installed power 2 640MW NPPs produce
53 of total produced electric energy
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Design in-core temperature measurements in
VVER-440 reactors

• Accuracy and Reliability of temperature
  measurements - important factors of safe and
  economical exploitation
• Level of design temperature measurement accuracy
  and reliability was continually increased

Output of fuel assemblies 216 TCs Circulation
loops 24 TCs and 12 RTDs
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Calibration procedure of in-core measurements

• Calibration during quasi-isothermal state of
  design temperature measurements
• QIS is adjusted with technology

• Calibration procedure
• QIS is reached and adjusted with technology
• Establishing an estimate average value calculated
  from non-calibrated design temperature
  measurements
• Comparison each temperature with calculated
  average corrections

• Drawback
• Missing metrologic link up
• Unknown quality of QIS

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SPAS
Important influence on the increasing of that
level had realisation of SPAS (designed by
VUJE) What is the SPAS? Monitoring system for
accuracy and reliability characteristics of
design temperature measurements in PWR/VVER-440
(SPAS abbr. from Slovak Sledovanie Presnosti
A Spolahlivosti Monitoring of the Accuracy And
Reliability)

• Most important features of SPAS
• calibration of design temperature measurements
  during quasi-isothermal states
• verification of design temperature measurements
  accuracy during power operation in each
  measurement cycle
• monitoring of temperature detectors condition
  during power operation
• data collection for evaluation of the accuracy
  and reliability of equipment
• dialog analysis of the accuracy and reliability

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Reactor temperature standard

• Autonomous measurement system installed on
  coolant loops
• Allows high accurate measurement of reactor
  coolant temperature
• Checks itself at each measuring cycle accuracy
  (random systematic deviations)
• reliability (circuit isolation resistances)

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Reactor temperature standard

• Its combined temperature detectors
• are installed in all reactor coolant loops
• are individually calibrated
• contain two resistance temperature detectors and
  three thermocouples
• are using four conductor connection

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Main output screen of reactor
temperature standard
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The binding between SPAS and in-core reactor
control system (as in Mochovce)
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SPAS

• Functions of SPAS
• temperature standard accuracy, determined in each
  measuring cycle during the whole fuel cycle
• validation of QIS quality
• corrections to the design temperature measurement
  results, obtained during QIS, including
  evaluation of their quality
• sensor databases of design measurements and the
  temperature standard including detailed data from
  the installation up to removal
• accuracy validation of temperature measurements
  by design system in each measuring cycle, during
  the reactor power operation

• Advantages
• capability to provide metrologic basement,
  automatic control of measuring channels accuracy
  and reliability during fuel cycle
• explanation of anomalous states during reactor
  fuel cycle
• monitoring of detectors characteristics and
  measuring lines long term changes

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Main output screen of SPAS
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Monitoring of output fuel assemblies temperatures
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Monitoring of temperatures in the loops
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Instrument database of in-core reactor
temperature sensors
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Histogram of correction constants during QIS
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Conclusion

• Systems SPAS is applied on two units with V-230
  reactors at NPP Bohunice and two units with
  reactors V-213 at NPP Mochovce
• Useful support to the IC staff for continual
  monitoring of design temperature measurements
  quality, and for the staff of reactor physics and
  technology works as effective tool for
  clarification of anomalous situations in the
  units
• Described systems were elaborated and applied in
  close co-operation with IC and physics staff in
  mentioned NPPs