Abstract
In order to improve the prediction of heavy actinide concentration in reactor fuel elements and to study the reduction of the long-term nuclear waste radiotoxicity by using transmutation, cross sections for neutron induced reactions are highly required by nuclear industry for many minor actinides. In this context, a new measurement of the Cm-245(n,f) cross section has been performed at the GELINA neutron facility of the Institute for Reference Materials and Measurements (IRMM) in Gee], Belgium. This measurement was motivated by the fact that in the thermal region a strong dispersion between measurements is observed and in the resolved resonance region, only a few old measurements exist with in some cases a poor energy resolution. The energy of the neutrons is determined applying the time of flight method using a flight path length of about 9 m. In the present work, the incident neutron energy covers the resolved and unresolved resonance regions up to a few keV. A highly enriched Cm-245 sample (98.48%) was mounted back-to-back with a B-10 sample in the centre of a vacuum chamber together with two surface barrier detectors positioned outside the neutron beam. One detector measured the B-10(n,alpha)Li-7 reaction products for the neutron flux determination, while the second one registered the Cm-245(n,f) fragments. In this way, the neutron flux can be determined simultaneously with the fission fragments. A control measurement has been performed replacing the Cm-245 sample with a U-235 sample in order to check that the well-known U-235(n,f) cross section can be reproduced. In comparison with previous Cm-245 fission cross section measurements, our results show a nice improvement of the energy resolution, in particular below 20 eV. A new set of resonance parameters is determined using the evaluation code CONRAD which was recently developed by CEA-Cadarache.
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