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Measurement of the 241 Am(n,2n) reaction cross section using the activation method

Measurement of the 241 Am(n,2n) reaction cross section using the activation method. G. Perdikakis 1,2 , C. T. Papadopoulos 1 , R. Vlastou 1 , A. Lagoyannis 2 , A. Spyrou 2 , M. Kokkoris 1 , S. Galanopoulos 1 , N. Patronis 1 , D. Karamanis 3 , Ch. Zarkadas 2 , G. Kalyva 2 , and S. Kossionides 2.

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Measurement of the 241 Am(n,2n) reaction cross section using the activation method

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  1. Measurement of the 241Am(n,2n) reaction cross section using the activation method G. Perdikakis1,2, C. T. Papadopoulos1, R. Vlastou1, A. Lagoyannis2, A. Spyrou2, M. Kokkoris1, S. Galanopoulos1, N. Patronis1, D. Karamanis3, Ch. Zarkadas2, G. Kalyva2, and S. Kossionides2 n_TOF Collaboration 1 Department of Physics, National Technical University of Athens, Athens, Greece 2Institute of Nuclear Physics, NCSR “Demokritos”, Athens, Greece 3 Department of Physics, University of Ioannina, Ioannina, Greece G. Perdikakis

  2. Outline of the talk • Motivation • Experimental • Analysis • Results for 241Am(n,2n) • Theoretical Calculations (in progress) • Other reactions studied – Future Plans G. Perdikakis

  3. Not enough experimental data ! Theoretical Predictions Transmutation of MAs - Important Reaction Channels • Neutron emission channels σ(n,xn) σ(n,xnf) • Fission Channels Experimental Investigation of Theoretical Model Parametres required G. Perdikakis

  4. 241Am: One of the most abundant isotopes in nuclear waste and one of the most radiotoxic elements Existing Data G. Perdikakis

  5. 241Am(n,2n)240Am Energy Range of Interest: 8-12 MeV G. Perdikakis

  6. Shielding wall Monoenergetic Neutron Beams @ INP “Demokritos” 5.5MV Tandem VdG p+ or d+ beam ~ 105n/cm2s 7Li(p,n)7Be 150 – 650 keV ~ 106n/cm2s 2H(d,n)3He 5 – 12 MeV ~ 105n/cm2s 3H(d,n)4He 16 – 20 MeV G. Perdikakis

  7. The Activation Target 3mm Pb shield 27 Al foil n Beam 37 GBq 241 Am target Stainless Steel G. Perdikakis

  8. Pb HPGe Irradiation Setup D filled Gas Cell d+ 9cm ΔΕn: < 100 keV n Beam 241Am Target 2 m Parafin BF3 Neutron Counter G. Perdikakis

  9. n+241Am n+241Am 240Pu Outline of the Reaction 241Am(n,2n)240Am Fission E,J,π 3n+239Am n T1/2=50.8h 2n+240Am γ 242Am Most Intense γ-rays: 5 days of irradiation for each beam energy ! 987.8 keV (I=73%) 888.8 keV (I=25%) G. Perdikakis

  10. 987.8 keV 240Am 154Eu 1014.7 keV 241Am 955.7 keV 241Am 984.5 keV 238Np +154Eu HPGe spectrum @ 10.6 MeV

  11. Reaction Cross Section G. Perdikakis

  12. Results G. Perdikakis

  13. G. Perdikakis et al. , Phys. Rev. C - In press Results G. Perdikakis

  14. n+241Am n+241Am 240Pu Outline of the Reaction 241Am(n,2n)240Am Fission E,J,π 3n+239Am n T1/2=50.8h 2n+240Am γ 242Am Hauser Feshbach: Preequilibrium contribution : Exciton Model STAPRE/F G. Perdikakis

  15. n+X The double-humped fission barrier ρΝ ρΑ ρΒ Saddle A states Saddle B states Normal states Fission n ħωΑ ħωΒ UA UB scission βΝ βΒ βΑ Deformation, β G. Perdikakis `

  16. Main parametres of the calculation • Level Density, ρ(U,J), at the saddles and at normal deformation • Transmission Coefficients for neutrons,Τn Coupled Channels OMP for actinides (Ignatyuk et. al. Sov. J. Nucl. Phys. 51, (5), 1990) • Fission Barrier Parametre UA,UB,ħωΑ,ħωΒ Deduced from experimental data (V. M. Maslov. RIPL-1 Handbook. TEXDOC-000, IAEA, Vienna, 1998, Ch. 5.) G. Perdikakis

  17. Shell, Superfluid pairing and Collective effects, important for the calculation a=ã[1+δw·f(U-Econd)] Generalized Superfluid Model of the nucleus Ignatyuk et al, Sov. J. Nucl. Phys 29, (4), 1979 G. Perdikakis

  18. 241Am(n,F) Results Preliminary !!! 241Am(n,2n) G. Perdikakis

  19. Conclusions Measurement of the 241Am(n,2n) reaction @ En = 8.8 – 11.4 MeV 241Am(n,2n) Theoretical calculations in progress 241Am(n,F) Other measurements • 232Th(n,2n) D. Karamanis et al. NIM A 505, 381, (2003) • n-induced reactions on Ge, Hf and Ir isotopes In progress • 237Np(n,2n) To be done G. Perdikakis

  20. THE END

  21. Results Preliminary !!! 241Am(n,2n) G. Perdikakis

  22. Conclusions and Future Perspectives • Systematic Experimental Investigation of 241Am(n,2n) Reaction Cross Section, for the first time • Consistent Theoretical Description of 241Am(n,2n) Reaction, in Reasonable Agreement with Experimental Data. • Experimental Investigation to be Continued at Lower Energies • Improvement of Theoretical Description over the whole energy range

  23. 241Am(n,2n)240Am

  24. Results 241Am(n,f) 241Am(n,2n)240Am

  25. Higher Fission/Capture ratio More effective Transmutation Main Characteristics • Sub-critical Systems • Transmutation of Nuclear Waste • Neutrons produced by Spallation Reaction in Accelerator S. Taczanowski et. al. Applied Energy 75, 97, (2003) Minor Actinides (Am, Cm, Np) • Not enough delayed neutrons Not a good reactor fuel Energy Production and Nuclear Waste Transmutation in ADS Systems Neutron Flux in Reactor Core affected by n-induced reactions

  26. Off Line HPGe 241Am Target Pb shielding

  27. Neutron Flux vs Time 5000000 4000000 3000000 Neutron Flux (counts) 2000000 5 days of Irradiation 1000000 Parafin E = 10.6 MeV 0 n 0 100000 200000 300000 400000 Irradiation Time (sec) Irradiation Setup D filled Gas Cell d+ n Beam 241Am Target BF3 Neutron Counter

  28. Neutron Flux vs Time 5000000 4000000 3000000 (counts) Neutron Flux 2000000 5 days of Irradiation 1000000 E = 10.6 MeV 0 n 0 100000 200000 300000 400000 Irradiation Time (sec) Mapping the Neutron beam fluctuations

  29. Pb HPGe

  30. Measurement of the 241Am(n,2n) cross section by the activation method ExperimentalDifficulties • Highly radioactive target, • Relatively long half life of 240Am (50.8 h)

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