Measurement of the 236U(n,f) cross section as a function of the neutron energyC. Wagemans1, L. De Smet1, S. Vermote1, J. Heyse2, 3, O. Serot4 and J. Van Gils2
1 Dept. of Subatomic and Radiation Physics, University of Gent, 9000 Gent, Belgium
2 EC-JRC-Institute for Reference Materials and Measurements, 2440 Geel, Belgium
3 SCK°CEN, 2400 Mol, Belgium
4 CEA Cadarache, DEN/DER/SPRC/LEPh, 13108 Saint-Paul-lez-Durance, France
Published online: 21 May 2008
The 236U(n,f) cross section has been measured in the neutron energy region from 0.5 eV to 25 keV at the GELINA neutron facility of the IRMM in Geel, Belgium. A highly enriched 236U sample was mounted back-to-back with a 10B sample in the centre of a Frisch-gridded ionisation chamber; a control measurement was performed with a 235U sample in the same configuration. Besides a dominant resonance at 5.45 eV, for which a resonance analysis was performed, the next resonance (cluster) only occurs at about 1.3 keV. It is demonstrated that the fission resonance integral and the thermal fission cross section adopted in all commonly used evaluated data libraries are too large by two orders of magnitude.
© CEA 2008