Neutron capture and fission reactions on 235U: cross sections, α-ratios and prompt γ-ray emission from fission

Abstract

According to the international benchmarks, and as it is mentioned in the NEA High Priority Request List, the 235U(n,γ) cross section is of utmost importance for the operation and design of current and advanced nuclear reactors. The required accuracy in this energy region (100 eV to 2.25 keV) ranges between 5% and 7%, to be compared with the present differences of 20% between the α-ratios in different evaluations. At n_TOF we have measured this cross section during the summer of 2012 using a fission tagging capture set-up. This new set-up has been tested successfully in 2010 and combines the n_TOF 4π Total Absorption Calorimeter with a series of MicroMegas fission detectors. The experiment has provided as well very valuable information on the distribution of energies and multiplicities of the γ-rays emitted prompt after capture and fission reactions. The very fresh data from this experiment will be presented for the first time, and their quality and expected results will be discussed in detail