Measurement of the ²³⁶U(n,f) Cross Section in the Neutron Energy Range from 0.5 eV up to 25 keV

The ²³⁶U(n,f) cross section has been measured in the energy range from 0.5 eV to 25 keV at the Geel Electron Linear Accelerator neutron time-of-flight facility of the Institute for Reference Materials and Measurements in Geel, Belgium. A highly enriched ²³⁶U sample was mounted back-to-back with a ¹⁰B sample in the center of a Frisch-gridded ionization chamber, hence realizing a 2 detection geometry. A ²³⁵U(n,f) cross-section control measurement was performed in the same experimental conditions. Special attention has been given to the fission resonance integral I_f and to the strongest resonance at 5.45 eV, for which a resonance analysis has been performed yielding _f = 1.7 eV. Both values are highly overestimated in the literature.