Measurement of the U(n, f) cross section relative to the Li(n, t) and B(n, ) standards from thermal to 170 keV neutron energy range at n_TOF

Amaducci, S.*; Harada, Hideo   ; Kimura, Atsushi   ; 118 of others*

The U(n, f) cross section was measured at n_TOF relative to Li(n, t) and B(n, ), in a wide energy range (25 meV170 keV) with 1.5% systematic uncertainty, making use of a stack of six samples and six silicon detectors placed in the neutron beam. The present results indicate that the cross section in the 918 keV neutron energy range is indeed overestimated by almost 5% in the recently released evaluated data files ENDF/B-VIII.0 and JEFF3.3. Furthermore, these new high-resolution data confirm the existence of resonance-like structures in the keV neutron energy region. From the present data, a value of 249.71.4(stat)0.94(syst) b eV has been extracted for the cross section integral between 7.8 and 11 eV, confirming the value of 247.53 b eV recently established as a standard.