Speaker
Mr
Raul Sarmento
(Instituto Tecnologico e Nuclear (ITN) - Lisbon - Portugal)
Description
Accurate knowledge of the U-236 neutron-induced fission cross-section is important for the development of accelerator-driven systems and fast reactors based on the Th-U cycle. The evaluated data presently stored in the nuclear data libraries rely on old measurements and show large discrepancies in the energy region between 1 keV and 100 keV. Recent measurements yielded results which are in disagreement with the literature for the resonance region and below 10 eV.
A new measurement of the 236U(n,f) cross-section was performed at the neutron Time-Of-Flight facility n_TOF at CERN, Geneva. A Fast Ionization Chamber has been used to determine the 236U(n,f) cross-section relative to the standard 235U(n,f) cross-section. Six resonance structures in the resonance and intermediate energy regions have been observed following the event reconstruction analysis, which included the subtraction of the 235U contamination in the sample together with the alpha-particle background, as well as the dead-time and detection efficiency corrections.
In this talk, a detailed report on the 236U(n,f) cross-section measurement at n_TOF will be given. The present high-resolution results point to several shortcomings in the current evaluations in the sub-threshold region and provide the basis for a re-evaluation of the cross-section.
Author
Mr
Raul Sarmento
(Instituto Tecnologico e Nuclear (ITN) - Lisbon - Portugal)
Co-author
Mr
Marco Calviani
(CERN)
