Verification of Important Cross-Section Data*
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Verification of ImportantCross-Section Data*
E.T. ChengSolana Beach, California
IAEA Technical Meeting on Nuclear Data for IFMIF4-6 October 2005
FZK, Karlsruhe, Germany
*Work Supported by the USDOE, Office of Fusion Energy Sciences
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Verification of Fusion Nuclear Data
• Continuing Efforts in Nuclear Data Development Have Made Fusion Design Less Uncertain
• Integral Neutronics Experiments Being Performed for ITER and Power Plant Development
• Nuclear Data Measurements Needed to Verify Important Evaluated Cross Sections
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Verification of Important Cross Sections
• Si28(n,n’p)Al27
• V51(n,n’p)Ti50
• Helium Production Data
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Si28(n,n’p)Al27• Si28(n,n’p)Al27 Reaction leads to Production of
Long-lived Radionuclide Al26(7.17x105 y half-life; gamma-emitter)
• Low Level Waste Disposal Rating: Ratio of Activation Level to the Limiting Activity for Low Level Waste
• Calculations of Al26 Production in SiC Using the Best Evaluated Nuclear Data Result in a (Class C) Low Level Waste Disposal Rating of 0.5 after Lifetime Irradiation of SiC in a Fusion Power Reactor
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Measurements of Si28(n,n’p)Al27• Activation Method
– Suggested by Hermann Vonach, Successfully Detected Nb as an Impurity in Vanadium [Nb93(n,2n)Nb92m]
– Required High-purity Si Samples– Detecting Na24 Activity [Si28(n,n’p)Al27(n,α)Na24]
• Proton Measurements– Thin Si Samples– Measuring Total Si28(n,xp) Cross Sections– Subtracting Si28(n,p) from Si28(n,xp)
• Measurements Performed at 14 MeV Energy and Above
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Measurements of Si28(n,n’p)Al27(Activation Method)
• High-purity Si Samples– Al27 Production Concentrations: ~0.05 appb (1
h); ~1.3 appb (1 d); and ~40 appb (30 d) [1011 n/s/cm2]
• Irradiate Samples for Several Hours and Detect Na24 [Al27(n,α)] Activity to Determine Al Content
• Verify Purity of Si Samples (Al/Si Must be < 1 appb)
• For Confirmed Pure Si Samples, Continue Irradiation for Weeks or Months and Measure the Increase of Na24 Activity
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Source: D. Rockman, et al. NNDC, BNL (2005)
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V51(n,n’p)Ti50
• Inaccurate V51(n,n’p)Ti50 Cross Section leads to an Overestimate of Hydrogen Production in the Vanadium Alloy, and Transmutation Product Ti
• Prediction of Vanadium Alloy Life Time Depends on the Accuracy of the Cross Section– Hydrogen Embrittlement– Degradation in Structural Properties
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Measurements of V51(n,n’p)Ti50
• Proton Production Cross Sections– Thin V Samples– Measuring Total V51(n,xp) Cross Sections– Subtracting V51(n,p)Ti51 from V51(n,xp)
• Measurements Performed at 14 MeV Energy and Above
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Materials Testing with IFMIF• IFMIF can Produce High Neutron Flux to
Reach Needed Helium Concentrations and Atomic Displacements (DPA) for Materials Damage Assessment in a Reasonable Time
• Helium to DPA in IFMIF Neutron Spectrum is Estimated to be Similar to that in a D-T Fusion Neutron Spectrum
• Helium Production Cross Sections are Fundamental to the Radiation Damage Assessment
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Helium Production Data for IFMIF
Verify Helium Production Data with IFMIF and D-T 14 MeV Neutron Sources
• Irradiate Samples at the 14 MeV Neutron Sources and IFMIF-like Facilities
• Measure Helium Contents
• Derive Helium Production Cross Sections and Compare to Evaluations (or Calculations)