Statistical analysis of cross sections—A new tool for data validation

Several neutron activation cross section libraries have been produced recently with data above the energy of 20 MeV. These are needed because of new applications, such as the International Fusion Material Irradiation Facility (IFMIF) and Accelerator Driven Systems (ADS). A standard validation procedure for such libraries is a comparison with differential and integral experimental data. However, the number of differential data above 20 MeV is relatively small and there are very few integral experiments with neutron spectra dominated by high-energy (>20 MeV) neutrons. Furthermore the size of these libraries (about 775 targets and >60,000 reactions) favours global test procedures. It is shown that the method of ‘Statistical analysis of cross sections’ (SACS) can be used for this purpose. This is based on the assumptions that cross section excitation curves for all targets have a similar (bell) shape shifted by differences in Q-value, and that their properties, such as the maximum of the excitation curve (σmax), the incident neutron energy at which σmax occurs (Emax) and the width of the excitation curve at half its maximum (Δ1/2) have a pronounced smooth trend as a function of A or s. It will be demonstrated that this method of analysis is a very effective and novel way to validate reaction cross section data, both for their shape and their magnitude. This will be illustrated using the recent European Activation Library EAF-2005, produced within the EFDA Fusion Technology Programme. The majority of the cross section data in the library are based on calculations with the nuclear reaction code TALYS.