A Study on Replacing AmBe Sources with Cf252 or 14MeV Neutrons

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A Study on Replacing Am-Be Sources with Cf-252 or
14-MeV Neutrons

• Cody Peeples

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Compensated Neutron Logging

• Uses two detectors
• The diffusion theory result for a point source in
  an infinite medium
• Is the theoretical underpinning of CNL
• Ls is related to the Hydrogen Index, IH
• Is a good approx. for r2 gt 70 cm
• Due to great distance, thermal flux is used
• Unfortunately b/c, Cl, B, Gd, etc. have great
  effect

For more info see Well Logging for Physical
Properties, Hearst 2000
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CNT-X
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CNT-14
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LWD Neutron Porosity Tool Operating Curve
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Porosity Correlation D-T Source

• Sandstone
• Note uncertainty gtgt! beyond 15 p.u.
• Variance not constant, depends on porosity
• Was calculated w/ isotropic source

• Limestone

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Porosity Correlation Cf252

• Limestone

• Sandstone

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Segmented Tally Design Method

• One detector type at a time
• Near, or
• Far
• Extend length
• Tally rxn rates in 5 cm long segments
• Choose segments carefully
• comparison with traditional simulation

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Accuracy of the Segmental Tally Design Method
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Accuracy of the Segmental Tally Design Method
Contd.
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This linear correlation is used as a correction
to optimize far detector spacing with the
segmented method
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Additional work

• Apply segmented tally design method to
• D-T Acc
• D-D Acc
• Cf-252
• Optimize spacing for maximum precision
• Comparison
• Requires additional considerations
• e.g. actual count rates (scaled by source
  intensity)