verification of important cross-section data*

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

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

Verification of Important Cross Sections

• Si28(n,n’p)Al27

• V51(n,n’p)Ti50

• Helium Production Data

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

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

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

Source: D. Rockman, et al. NNDC, BNL (2005)

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

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

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

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)