The European Activation File: EAF-2007 neutron-induced cross section library
In the European fusion programme, safety and environmental issues are of great importance in the continuing development of power plants. In support of this programme, a sound, complete and reliable neutron-induced cross section data library is required. The European Activation File (EAF) project has been an ongoing process performed through European and world-wide co-operation that has led to the creation of succeeding EAF versions. The latest release, EAF-2007, in a significant change from previous versions includes cross section data for deuteron- and proton-induced reactions. As with EAF-2005 all cross sections have an upper energy limit of 60 MeV. EAF-2007 has benefited from the generation and maintenance of comprehensive activation files and the development of the processing code SAFEPAQ-II. Cross section validation exercises against both experimental data and systematics, which were started on the EAF-4 file (1995), enable a comprehensive assessment of the data. SAFEPAQ-II is used to apply a series of modifications to the original source data. A very important set of modifications concerns renormalisation and branching using experimental or systematic data. A total of 8,276 reactions have been so changed; 12% of all the reactions. These are challenging tasks when the source contains nonthreshold reactions with an energy dependent branching ratio. Although EAF-2007 is the best-validated cross section library in the world, currently less than 3% of all the reactions can be compared with experimental information, and sometimes then only for very limited, and not always fusion relevant, energy ranges. As with EAF-2001, -2003 and -2005, results of integral experiments have been used to correct, adjust and validate data. This can be done using SAFEPAQ-II by inputting the measured effective cross sections. Validation using integral data has been performed by means of direct comparison with measurements of various materials under fusion-relevant neutron spectra. Irradiations have been carried out at ENEA FNG, FZK Isochron-cyclotron, Sergiev Posad SNEG-13, TUD, Rež and JAERI FNS and integral C/E comparisons made (C/E is the ratio of the library to the experimental value). In addition available data from the literature, particularly for neutrons above 20 MeV have been collected and used. The results of these benchmarking exercises have indicated, in conjunction with differential data, where modifications to the data can be applied. The EAF-2007 library contains 65,565 excitation functions involving 816 different targets from 1H to 257Fm, atomic numbers 1 to 100, in the energy range 10-5 eV to 60 MeV. The 3,591,351 lines that make up the point-wise file are then processed into numerous group-wise files with different micro-flux weighting spectra to meet various user needs. Uniquely, an uncertainty file is also provided that quantifies the degree of confidence placed on the data for each reaction channel.