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1 OPTIMIZATION OF ACTINIDE QUANTIFICATION BY ELECTRON PROBE MICROANALYSIS Aurélien Moy Claude Merlet (UM2/GM) Xavier Llovet (Universitat de Barcelona/CCiTUB)

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Presentation on theme: "1 OPTIMIZATION OF ACTINIDE QUANTIFICATION BY ELECTRON PROBE MICROANALYSIS Aurélien Moy Claude Merlet (UM2/GM) Xavier Llovet (Universitat de Barcelona/CCiTUB)"— Presentation transcript:

1 1 OPTIMIZATION OF ACTINIDE QUANTIFICATION BY ELECTRON PROBE MICROANALYSIS Aurélien Moy Claude Merlet (UM2/GM) Xavier Llovet (Universitat de Barcelona/CCiTUB) Olivier Dugne (CEA/DEN) June 24 th, 2013

2 Context EPMA uses in the nuclear field: Quantitative characterization of actinides. 2 Actinides characterization in spent fuel MOX fabrication and characterization Conception of Gen IV fuel Analysis of serious accidents However, quantitative analysis is not always possible due to the lack of standard samples. Solution: calculated standards. To be reliable, these calculations require accurate atomic data and especially accurate x-ray production cross-section. June 24 th, 2013

3 Electron Probe Quantitation 3 a beam of electrons is fired at a sample the beam causes each element in the sample to emit X-rays at a characteristic energy characteristic x-ray intensities are proportional to the mass fraction of each emitting element present in the sample June 24 th, 2013

4 Standard intensity 4 June 24 th, 2013 [1] C. Walker, Electron probe microanalysis of irradiated nuclear fuel: an overview, J. Anal. At. Spectrom., 1999, 14, 447-454.

5 Calculated standard 5 The x-ray production cross section is not well known especially for heavy elements and needs new evaluations. Calculated intensity on a bulk sample can be expressed by : Number of target atoms per unit volume Number of primary electrons reaching the target X-ray production cross-section Secondary fluorescence Number of photon emerging from the sample Spectrometer efficiency June 24 th, 2013

6 X-ray production cross-section 6 L (resp. M) x-ray lines are emitted when a vacancy in the L (resp. M) shell is filled by an electron from an outer shell.

7 Measurements method 7 On a thin auto-supported sample, the equation reduces to: June 24 th, 2013

8 X-ray intensity measurement 8 Thin auto-supported sample were used: high signal-to-noise ratio no electron backscattering no photon absorption into the sample. Samples composition: 1nm thick layer of the active material deposited on 5nm thick self-supporting carbon backing film. To ensure a good counting statistic, x-ray intensities were recorded at 60 different positions during 600s. Deposit Auto-supported carbon layer Grid Faraday cage Statistical uncertainties were about 4% or 5% for the lowest intense lines. June 24 th, 2013

9 X-ray intensity measurement 9 June 24 th, 2013

10 Target thickness determination 10 Thickness determination: measurement of the k-ratio (ratio between the emitted x-ray intensity from the sample and from a tick standard target) versus electron beam energy. analysis of the k-ratio by the EPMA software X-film. Uncertainty on the determination of the thinnest target thickness (1.94µg/cm²) < 5%. June 24 th, 2013

11 Spectrometer efficiency 11 Spectrometer efficiencys uncertainty < 5%. June 24 th, 2013

12 12 Results: uranium L-shell x-ray production cross section 12 Total uncertainties for the Lα line was estimated to be 10%. Lα x-ray production cross section was recorded from the ionization threshold up to 38 keV. No experimental data were found for comparison. June 24 th, 2013

13 Results: lead L-shell x-ray production cross sections 13 Total uncertainties were estimated to be 7% and 7.5% for the Lα and Lβ lines, respectively. [2] A. Moy, C. Merlet, X. Llovet and O. Dugne, 2013, J. Phys. B: At. Mol. Opt. Phys. 46, 115202. [3] Y. Wu, Z. An, Y. M. Duan, M. T. Liu et C. H. Tang, 2007, J. Phys. B: At. Mol. Opt. Phys. 40, 735. Lα and Lβ x-ray production cross sections were recorded from the ionization threshold up to 36 keV [2]. Experimental results were compared with the only set of experimental data found in the literature [3]. June 24 th, 2013

14 DWBA cross-section 14 Theoretical ionization cross sections were calculated by Bote et al. [4] into the distorted-wave Born approximation (DWBA) theory. Ionization cross sections were converted into x-ray production cross sections with atomic relaxation data extracted from the Evaluated Atomic Data Library (EADL). [4] D. Bote, F. Salvat, A. Jablonski and C. J. Powell, 2009, At. Data Nucl. Data Tables 96, 871. June 24 th, 2013

15 Results: lead M-shell x-ray production cross sections 15 Total uncertainties were estimated to be 6.5% and 7% for the Mα and Mβ lines, respectively. Mα and Mβ x-ray production cross sections were recorded from the ionization threshold up to 38keV. Grey shaded areas represent the uncertainty bands of the converted Bote et al. DWBA calculation. June 24 th, 2013

16 Results: lead M-shell x-ray production cross sections 16 Total uncertainty was estimated to be 12% for the M line. The shape of the experimental curve is in good agreement with the DWBA calculation. June 24 th, 2013

17 Results: uranium 17 Total uncertainties were estimated to be 9.5% and 8.5% for the Mα and Mβ lines, respectively. Experimental results are in very good agreement with theoretical DWBA cross sections in shape and magnitude. June 24 th, 2013

18 Results: uranium 18 Total uncertainty was estimated to be 15% for the M line. M experimental results agree with the theoretical DWBA cross-section. June 24 th, 2013

19 Conclusion and perspectives 19 L and M x-ray production cross sections are in good agreement with other experimental data (Pb L-shells) with converted theoretical DWBA cross sections. DWBA model good candidate to calculate x-ray production cross sections for the conception of calculated standards (standardless analysis). The x-ray production cross-section represents one term in the calculated standard intensity To obtain absolute intensity, other terms have to be carefully evaluated. X-ray production cross sections for Th will be measured prediction of the DWBA model will also be tested. Virtual standards will be set up intensity predictions for Pu, Np and Am will be tested (with measured intensity) to asses the reliability. June 24 th, 2013

20 Thank you for your attention June 24 th, 2013


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