[en] This thesis work consists in two parts. The first part is the description of the creation of a photonuclear activation file which will be used to calculated photonuclear activation. To build this file we have used different data sources: evaluations but also calculations done using several cross sections codes (HMS-ALICE, GNASH, ABLA). This file contains photonuclear activation cross sections for more than 600 nuclides and fission fragments distributions for 30 actinides at tree different Bremsstrahlung energies and the delay neutron spectrum associated. These spectra are not in good agreement with experimental data. That is why we decided to launch measurement of delayed neutrons spectra from photofission. The second part of this thesis consists in demonstrating the possibility to do such measurements at the ELSA accelerator facility. To that purpose, we have developed the detection, the acquisition system and the analysis method of such spectra. These were tested for the measurement of the delayed neutron spectrum of uranium-238 after irradiation in a 2 MeV neutron flux. Finally, we have measured the delayed neutron spectrum of uranium-238 after irradiation in a 15 MeV Bremsstrahlung flux. We compare our results with experimental data. The experiment has allowed us to improve the value of ν_p-bar with an absolute uncertainty below 7%, we propose ν_p-bar = (3.03 ± 0.02) n/100 fissions, and to correct the Nikotin's parameters for the six group representation. Particularly, we have improved the data concerning the sixth group by taking into account results from different irradiation times

[en] This thesis work consists in two parts. The first is the description of the creation of a photonuclear activation file which will be use to calculated photonuclear activation. To build this file we used different data sources: evaluations but also calculations done using several cross sections codes (HMSALICE, GNASH, ABLA). This file contains photonuclear activation cross sections for more than 600 nuclides and fission fragments distributions for 30 actinides at tree different Bremsstrahlung energies and the delay neutron spectrum associated. These spectra are not in good agreement with experimental data. That is why we decided to launch measurement of delayed neutrons spectra from photofission. The second part of this thesis consists in demonstrating the possibility to do such measurements at ELSA For that we developed the detection, the acquisition system and the analysis method of such spectra. These were tested for the measurement of the delayed neutron spectrum of uranium-238 after irradiation in a 2 MeV neutron flux. After all, we measured the delayed neutron spectrum of uranium-238 after irradiation in a 15 MeV Bremsstrahlung flux. We compare our results with experimental data. (author)

[en] This document describes the method used to compute the activation of the structure components near the electron-positron converter of the Lure accelerator (Orsay). Activation comes from photon and neutron reactions on nuclei belonging to the concrete structure. Only radio-nuclides with a half-life greater than 200 days are considered penalizing for dismantling operations. The main photonuclear reactions produce the following nuclides: Na²², Cl³⁶, Mn⁵⁴, Nb⁹², Ba¹³³, Co⁵⁷ and Co⁶⁰. The main neutron reaction generate the following nuclides: H³, C¹⁴, Cl³⁶, K⁴⁰, Co⁶⁰, Ni⁶³, Zn⁶⁵, Se⁷⁹, Zr⁹³, Ag¹⁰⁸, Ag¹¹⁰, Ba¹³³, Cs¹³⁴, Eu¹⁵², Eu¹⁵⁴, Fe⁵⁵, Ca⁴¹, Na²², Mn⁵⁴, Cs¹³⁷, Nb⁹² and Ti²⁰⁴. The MCNPX code has been used to compute the values of the photon and neutron fluxes received by the structure components, the activation has been computed with the Cinder code from the flux values. The main contributors for radioactivity on long term basis appear to be Ca⁴¹ and Ni⁶³. Calculations have been compared with the measurement of activities of 3 concrete samples drilled out from the structure. The results of the comparison are given for Co⁶⁰, Cs¹³⁴, Eu¹⁵² and Eu¹⁵⁴. The computed values appear to be greater by a factor varying from 2 to 5 which is consistent with the method used that naturally overestimates the activation. These results are considered as satisfactory for performing waste zone labelling. (A.C.)

[en] In this article we present the development of a photonuclear activation data library for CINDER'90. The IAEA evaluations for 164 nuclei are included explicitly and reactions for another ∝500 isotopes are added using the HMS-ALICE predictions. We also test the GNASH code for some evaluations in the case of actinides. Some preliminary calculations of photo-fission yields are done with the GSI fission-evaporation program. Finally, the transmutation analysis of nuclear waste in high photon fluxes is performed as a test case of the newly developed photonuclear data library. (orig.)

[en] This article presents calculations of photonuclear reaction cross sections for actinides by using different reaction codes, namely an improved version of HMS-ALICE and GNASH. The GDR parameters from the RIPL2 data library are used to describe the total photo-absorption cross section. In general, our results show satisfactory agreement with experimental data and IAEA evaluations. We plan to include our GNASH evaluations for ²³⁵U, ²³⁸U, ²³⁷Np, ²³⁹Pu, ²⁴⁰Pu and ²⁴¹Am into a new release of the ENDF-B/VII data files. (authors)