Luigi Mercatali mercatali@irs.fzk.de

1. On the accuracy in the theoretical prediction of neutron induced reaction cross-sections above 0.1 MeV Luigi Mercatali mercatali@irs.fzk.de Forschungszentrum Karlsruhe / Institute for Reactor Safety 2nd IP EUROTRANS Internal Training Course “Nuclear Data for Transmutation: Status, Needs and Methods” Santiago de Compostela (Spain), June 7-10, 2006 IP EUROTRANS Training Course Santiago de Compostela (Spain), June 7-10, 2006

2. IP-EUROTRANS • DM5: NUDATRA (NUclear DAta for TRAnsmutation) Improvement and assessment of the simulation tools and associated uncertainties for ADS transmuters and its associated fuel cycle The activity is essentially focused on the evaluated nuclear data libraries and reaction models for materials in transmutation fuels, coolants, spallation targets, internal structures, and reactor and accelerator shielding, relevant for the design and optimisation of the Generic ETD and XT-ADS • FZK contribution is related to: WP5.1 Sensitivity Analysis and Validation of Nuclear Data and Simulation Tools IP EUROTRANS Training Course Santiago de Compostela (Spain), June 7-10, 2006

3. Background • Nuclear data libraries are mainly focused on neutron induced reaction cross-sections up to 20 MeV. At present there is a significant effort to extend the energy range of the library up to 200 MeV in order to comply with recent developments in transmutation research with ADS’s. This extension is not trivial because of the increasing number of open channels. In addition, the scarcity of experimental data at intermediate energies requires to rely extensevely on model calculations • Results of model calculations should be provided together with the associated uncertainties • Arjan Koning has shown that it possible (in principle) to generate a complete covariance matrix for all neutron-induced reactions using random variations of nuclear model paramenters (via a Monte Carlo algorithm), following the original idea of D. Smith (ANL) IP EUROTRANS Training Course Santiago de Compostela (Spain), June 7-10, 2006

4. Background (cont’d) • Several open issues related to the approach of D. Smith: • Actual distribution of the model paramenters (Gaussian, …?) • Parameters correlations not only within one model, but also within paramenters of different models that have the same effect on a calculated quantity • Uncertainty due to nuclear models • How to disentangle uncertainties due to the models with the ones due to the model parameters • Comparison of massively calculated cross-sections against all the experimental data of the periodic table of elements would be needed in order to use the average deviations from experiments to assess the most pessimistic uncertainties for unmeasured reaction channels IP EUROTRANS Training Course Santiago de Compostela (Spain), June 7-10, 2006

5. Background (cont’d) H. Leeb et. al., Covariances for Evaluations Based on Extensive Modelling, Proc. ND2004, Santa Fe (USA) • uncertainties of the model parameters • errors due to numerical implementation • deficiencies of the model Minimization IP EUROTRANS Training Course Santiago de Compostela (Spain), June 7-10, 2006

6. Background (cont’d) Mean model error extracted from the reproduction of observable not included in the evaluation ; ; Ci,j obtained by intuition IP EUROTRANS Training Course Santiago de Compostela (Spain), June 7-10, 2006

7. Assessment of the predictive power of modern nuclear models • Comparison between experimental cross-sections and theoretical predictions • Calculations performed with the state of the art of nuclear models and simulation tools: • GNASH, TALYS, ALICE/ASH, HMS/ALICE, EMPIRE, MCNPX • Goals: • Provide recommendations on the best combinations of theoretical models and codes to optimize the accuracy of the simulations (as for different energy groups, as for different nuclides, as for different channels) • Comparison of nuclear models on a large variety of materials (from C up to transuranics) to improve the systematics of the model parameters IP EUROTRANS Training Course Santiago de Compostela (Spain), June 7-10, 2006

8. Experimental data • Processing of EXFOR via FORTRAN coding and X4TOC4 code: • All target nuclei with 13 ≤ Z ≤ 83 • Initial neutron energy above 0.1 MeV • All (n,xnypzα) reactions • Data excluded: • Out-dated and superceded measurements • Targets containing natural mixtures of isotopes • Reactions with metastable products • Data averaged for a wide range of neutron incident energies • (n,γ), (n,np), (n,nd) and (n,3He) reactions • Identical data IP EUROTRANS Training Course Santiago de Compostela (Spain), June 7-10, 2006

9. Experimental data (cont’d) • Total experimental points (Z,A,E): 17937 • Energy range: 0.1÷64.4 MeV • Points with projectile energy > 20 MeV: 615 • Reactions available: (n,n’), (n,p), (n,α), (n,t), (n,2n), (n,nα), (n,2p) (n,pα), (n,2α), (n,3n), (n,4n) other reactions noted in EXFOR as (n,x) IP EUROTRANS Training Course Santiago de Compostela (Spain), June 7-10, 2006

10. Calculations • TALYS and ALICE/ASH codes • Nuclear reaction simulations in the range 1 keV ÷ 200 MeV • Neutrons, protons, deuterons, tritons, helions, alphas and photons • All open reaction channels covered • Uncertainty assessment on the use of different phenomenological and microscopic nuclear level density models Numbers of nuclear levels per MeV around an excitation energy E IP EUROTRANS Training Course Santiago de Compostela (Spain), June 7-10, 2006

11. Nuclear level density calculation with TALYS and ALICE/ASH * at low energy of the excitation the “constant temperature” model is used. IP EUROTRANS Training Course Santiago de Compostela (Spain), June 7-10, 2006

12. Data Treatment Deviation factors can be provided as for single target nulide, energy, channel or groups of these IP EUROTRANS Training Course Santiago de Compostela (Spain), June 7-10, 2006

13. IP EUROTRANS Training Course Santiago de Compostela (Spain), June 7-10, 2006

14. H IP EUROTRANS Training Course Santiago de Compostela (Spain), June 7-10, 2006

15. Representation by A IP EUROTRANS Training Course Santiago de Compostela (Spain), June 7-10, 2006

16. TALYS and ALICE/ASH: Best performances by A IP EUROTRANS Training Course Santiago de Compostela (Spain), June 7-10, 2006

17. Evaluations vs. experiments IP EUROTRANS Training Course Santiago de Compostela (Spain), June 7-10, 2006

18. H- minimization procedure IP EUROTRANS Training Course Santiago de Compostela (Spain), June 7-10, 2006

19. Ongoing and future activities • Uncertainty assessment for proton induced reaction cross-section up to the highest energy for ADS applications (~ 1 GeV) The processing and the simulations of all (p,xnypzα) reactions up to 150 MeV is completed → ~ 19300 experiments IP EUROTRANS Training Course Santiago de Compostela (Spain), June 7-10, 2006

20. Ongoing and future activities (cont’d) • Extension of the assessment to transuranics target nuclei • Investigation of the performance of different tools: • EMPIRE, MCNPX (Bertini, ISABEL, INCL4, CEM2k models combined with pre-equilibrium exciton models and with evaporation Dresner and ABLA model) • Creation of a new activation library for proton induced reaction cross-sections based on the recommendations coming from the above analyses • Covariance studies via Leeb’s and Smith’s approaches • Global integral deviation factor: IP EUROTRANS Training Course Santiago de Compostela (Spain), June 7-10, 2006