Measurement of the Fission Cross Section of Uranium-235 for Incident Neutrons with Energies Between 2 and 100 keV

The fission cross section of 235U was measured for incident-neutron energies between 2 and 100 keV using an electron LINAC pulsed source of neutrons and the time-of-flight technique. The fission events were characterized by coincidence between the pulses of a fission chamber, placed at the center of a large scintillation tank, and gamma-ray events registered in the tank. The incident-neutron spectrum versus energy was monitored by a BF3 ionization chamber and checked with a 6Li-glass neutron detector. The cross sections were normalized to a value of 31 643 b-eV for the fission integral between 2 and 10 keV.Comparison of the present 235U fission cross-section results with the values from other sources shows, in general, there is an agreement within 3 to 5% in the energy region covered by this experiment.The previously reported intermediate structure in the fission cross section in the keV region is confirmed by the results of this work.