Laser Ablation Techniques for the Analysis of Key Radionuclides in Nuclear Decommissioning

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Laser Ablation Techniques for the Analysis of Key
Radionuclides in Nuclear Decommissioning

• David N. Douglas, Barry L. Sharp and Helen J.
  Reid
• The Centre for Analytical Science, Department of
  Chemistry, Loughborough University

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Topics

• Laser ablation
• LAIF - Laser Ablation In Fluid
• MALA - Matrix Assisted Laser Ablation

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What is Laser Ablation?
Viewing optics

• ICP-MS (coupled to a LA system)
• Elements 6Li - 241Am
• Limits of detection 10-100 ng/g
• Linear range over 6 orders of magnitude

Splitter
Optical window
Ablation cell
Ablated particles usually lt5 µm
Carrier gas (He or Ar)
Sample
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Calibration Strategies

• Direct liquid ablation
• Ablation of aqueous solutions spiked with
  internal standard

• Dual sample/standard
• Simultaneous introduction of ablated sample
  aerosol and nebulised aqueous standard

F Boué-Bigne, B J Masters, J S Crighton and B L
Sharp, J. Anal. At. Spectrom., 1999, 14, 1665
1672.
C OConnor, B L Sharp and P Evans, J. Anal. At.
Spectrom., 2006, 21, 556 565.
3 classes of calibration strategy

• Matrix matched solid standard
• Use of matrix matched standards often
  incorporating internal standardisation or isotope
  dilution

C OConnor, M R Landon and B L Sharp, J. Anal.
At. Spectrom., 2007, 22, 273 282.
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Management of Nuclear Waste for Disposal
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LA for Nuclear Applications
Decontamination of concrete 1
Simulated vitrified HLW waste in a steel
container 2

• Advantages of using LA in nuclear applications
• In-situ or laboratory based analysis.
• Safety and speed.
• Screening for unknowns.

1 http//www.dep.state.pa.us/dep/deputate/airwaste
/rp/Quehanna/HotCells2.htm 2 http//www.nda.gov.uk
/ukinventory/waste/waste-now-hlw.cfm
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Laser Ablation In Fluid (LAIF)
Solution collected for analysis
Lab-based analysis
Ablation plume

• Advantages of underwater laser ablation
• Higher ablation efficiency.
• Ablated material collected in solution safer as
  alpha and beta particles contained, not in an
  aerosol.
• Allows for solution based calibration of ejected
  material.
• Dissolution process reducing overall waste volume.

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Current Problems
Degassed water
Normal water

• Obstacles
• Cavitation leading to bubbles in solution
  resulting in interaction with the incoming laser
  beam.
• Smaller ablation site than spot size.
• Less material released as the different focal
  image gives roughly 9 times less material
  ejection.

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LAIF Preliminary Results
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In-situ LAIF

• New laser technologies
• The development of a stand off collection system.
• Material would be ablated in water where a water
  jet/collection cell would be used to capture the
  ablated particulate.

• Combining ablation and Laser Induced Breakdown
  Spectroscopy (LIBS)
• The ablation process through water can also be
  used with a LIBS based system.

LIBS
Collection cell
Collection cell
Liquid Jet
Liquid Jet
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Matrix Assisted Laser Ablation (MALA)

• Principle
• Use of a strongly absorbing binder matrix so that
  ablation yield is to a first approximation
  independent of the sample composition.
• Vanillic acid is material of choice for 213 nm
• Enables external calibration with non-matrix
  matched standards.
• Internal standardisation of isotope dilution also
  possible.

• Applications
• Analysis of powdered materials, sludges,
  sediments etc.

C OConnor, M R Landon and B L Sharp, J. Anal.
At. Spectrom., 2007, 22, 273 282.
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Management of Nuclear Waste for Disposal
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A Strategy for Sludge Analysis
Slurry, liquid phase pressed into binder
Sludge with vanillic acid binder on top
Sludge and vanillic acid binder mixed
Solid phase
Liquid phase
Pre-formed pot made from vanillic acid binder
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MALA Preformed Pots

• Advantages of a pre-formed sample pot
• Reduced volume of material
• Reduced contamination to the plunger and press
• Liquid phase retained in the vanillic acid,
  allows for analysis of liquid phase as well as
  solid.

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MALA Preliminary Results
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Acknowledgements
The DIAMOND consortium The EPSRC Centre for
Analytical Science, Department of Chemistry,
Loughborough
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