Presented by : Dr' Robert W' Mills, UK NNL'

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(No Transcript)
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A decay heat benchmark based on SKB published
calorimetric measurements of BWR and PWR spent
fuel assemblies by Robert Mills and Andrew
Sutton.
JEF/DOC-1272UKNSF(09)P235
Presented by Dr. Robert W. Mills, UK NNL.
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Outline

• Decay Heat Validation
• Current Status
• Recent published measurements
• Extended validation
• Purpose of this new benchmark document
• Future work

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Existing decay heat validation (1)

• Measurements of 24 fuel assemblies reported in
• F. Schmittroth, ORIGEN2 Calculations of PWR
  spent fuel decay heat compare with calorimeter
  data. HEDL-TME 83-32 UC-85 (1984)
• Assemblies from 3 reactors San Onofre,
  Point Beach and Turkey Point
• Whole assemblies measured.
• Burnup values of 25 to 40 GWd/t
• Cooling 2.4 to 8.2 years
• Enrichments 2.5 to 3.4 Wt U235.
• Measurements are reported to be 2

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Existing decay heat validation (2)

• 4 measurements removed due to reported
  inconsistencies.
• San Onofre stainless steel clad no data on
  cobalt content
• Expected to be between 120 and 1200 ppm
• Mean C/E at 1200 ppm was 1.09
• Mean C/E at 1000 ppm was 1.06
• Mean C/E at 120 ppm was 0.93
• Unless cobalt content know cant justify use.
• Only 12 measurements could be used for
  validation.

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Existing PWR decay heat validation
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Recent published SKB decay heat measurements (1)

• Reference Svensk Kärnbränslehantering AB,
  "Measurements of decay heat in spent nuclear fuel
  at the Swedish interim storage facility, Clab",
  SKB Report R-05-62, ISSN 1402-3091 (2006).
• Swedish Nuclear Fuel and Waste Management
  Company (SKB) have completed calorimetric
  measurements on BWR and PWR assemblies at the
  Swedish Interim Spent Fuel Storage Facility,
  CLAB, at Oskarshamn.
• 43 measurements of PWR assemblies and 66 of
  BWR assemblies.
• Estimate of accuracy between 1 and 2.

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Recent published SKB decay heat measurements (2)

• The PWR assemblies range in
• irradiation from 19.7 to 51.0 GWd/t
• cooling from 13 to 23 years and
• enrichment from 2.1 to 3.4.
• The BWR assemblies range in
• irradiation from 14.5 to 46.6 GWd/t
• cooling from 11 to 27 years and
• enrichment from 2.1 to 3.1.

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Recent published SKB decay heat measurements (3)

• This considerably extends the current FISPIN
  decay heat validation.
• 12 measurements gt 121 measurements
• PWR gt PWR and
  BWR
• Cooling 2.4 8.2 years gt 2.4 27 years
• Irradiation 25 40 gt 14.5 51
  GWd/t
• Enrichment 2.5 3.4 wt gt 2.1 3.4 wt

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SKB Calorimeter design
Water level
Calorimeter
Gamma Radiation Detectors
Recirculation Pump
Temperature sensors
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Modelling assumptions

• Published reactor design information
• 2D slice model through assembly
• WIMS/TRAIL/FISPIN route
• Neutron Cross sections from TRAIL database
  DB.WIMS172.6A_S5
• Assumptions
• PWR 500 ppm boron during whole irradiation
• BWR 40 void fraction during whole irradiation
• Structural materials irradiated in same flux as
  fuel

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PWR results (1)
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PWR results (2)
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PWR comparison
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BWR results (1)
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BWR results (2)
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BWR results (3)
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BWR comparison
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Overall C/E results ( 1 standard deviation)
BWR
PWR
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Decay Heat Calculated against Experimental
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Purpose of benchmark document (Issue 1)

• Reports reactor design parameters modelled
• Reports assembly design and irradiation
  information modelled
• Where necessary make reasonable assumptions
  for missing data.
• Should allow others to repeat validation and
• Review data used.
• Review methods used.
• Report data errors or differences in results from
  other methods.

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Future work

• Within NNL
• Improved data (JEFF-3.2?)
• Improved codes (WIMS10?)
• Improved modelling ?
• 3D model
• variation of axial void fraction with height
  during operation.
• Incorporating any errors found by others.
• Incorporating other validation results by others.

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Acknowledgements
The authors would like to thank the NDA for
funding this work.