Speaker
Description
For the improvement of Generation IV nuclear reactors simulation, accurate evaluated data are required. Among others, a reaction of interest is the neutron inelastic scattering as it modifies the energy distribution of neutrons. In the context of the innovated Th/U cycle and for a better knowledge of the neutron inelastic scattering on thorium 232, experiments have been performed at EC-JRC/GELINA.
Using the prompt gamma ray spectroscopy and the GRAPhEME device to detect the emitted photons, 70 $(n,n'\gamma)$ transition cross sections have been measured . From these cross sections and nuclear structure data, such as gamma intensities or internal conversion coefficients (ICC), one can determine inelastic level production cross sections and the total neutron inelastic scattering cross section. Assumptions had to be made regarding the multipolarity of several gamma transitions as they were not experimentally known. They enabled to exploit more data and obtain more level production cross sections.
The obtained cross sections, presented in this poster, have shown that conversion electrons are a relevant parameter. The misreading of this parameter and its associated uncertainty have a large impact on the total neutron inelastic scattering cross section uncertainty. There is also a need to probe deeper the thorium 232 nuclear structure in order to get more accurate inelastic level production cross sections.
Comparisons made with the nuclear reaction code TALYS, using default parameters and improved input data (TENDL files), have revealed that inelastic level production cross sections are not well predicted by the code. Studies are ongoing to improve the TALYS predictions.