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 ^(245)Cm(n,f) cross section has been performed at the GELINA neutron facility of the Institute for Reference Materials and Measurements (IRMM) in Geel, 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 ^(245)Cm sample (98.48%) was mounted back-to-back with a ^(10)B sample in the centre of a vacuum chamber together with two surface barrier detectors positioned outside the neutron beam. One detector measured the ^(10)B(n,α)^7Li reaction products for the neutron flux determination, while the second one registered the 245Cm(n,f) fragments. In this way, the neutronux can be determined simultaneously with the fission fragments. A control measurement has been performed replacing the ^(245)Cm sample with a ^(235)U sample in order to check that the well-known ^(235)U(n,f) cross section can be reproduced. In comparison with previous ^(245)Cm 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. KCI Citation Count: 0
The
236
U(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
236
U sample was mounted back-to-back with a
10
B sample in the center of a Frisch-gridded ionization chamber, hence realizing a 2π detection geometry. A
235
U(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 Γ
f
= 1.7 μeV. Both values are highly overestimated in the literature.
The emission probabilities and the energy distributions of tritons,
α and
6He particles emitted in the spontaneous ternary fission (zero excitation energy) of
250Cf and
252Cf and in the cold neutron ...induced fission (excitation energy
≈
6.5
MeV
) of
249Cf and
251Cf are determined. The particle identification was done with suited
Δ
E
–
E
telescope detectors, at the IRMM (Geel, Belgium) for the spontaneous fission and at the ILL (Grenoble, France) for the neutron induced fission measurements. Hence particle emission characteristics of the fissioning systems
250Cf and
252Cf are obtained at zero and at about 6.5 MeV excitation energies. While the triton emission probability is hardly influenced by the excitation energy, the
4He and
6He emission probability in spontaneous fission is higher than for neutron induced fission. This can be explained by the strong influence of the cluster preformation probability on the ternary particle emission probability.
The emission probabilities and the energy distributions of tritons and
α particles emitted in the spontaneous ternary fission (zero excitation energy) of
244Cm,
246Cm and
248Cm and in the cold ...neutron induced fission (excitation energy
≈
6.5
MeV
) of
243Cm,
245Cm and
247Cm are determined. The particle identification was done with suited
Δ
E
−
E
telescope detectors, at the IRMM (Geel, Belgium) for the spontaneous fission and at the ILL (Grenoble, France) for the neutron induced fission measurements. Hence particle emission characteristics of the fissioning systems
244Cm,
246Cm and
248Cm are obtained at zero excitation energy and at an excitation energy around 6.5 MeV. Whilst the triton emission probability is hardly influenced by the excitation energy, the
4He emission probability in spontaneous fission is about 20% higher than for neutron induced fission. This could be explained by the influence of the cluster preformation probability on the ternary
α emission.
13pSC-12 Fission of proton-rich nuclei Andreyev, A.; Elseviers, J.; Huyse, M. ...
Meeting Abstracts of the Physical Society of Japan,
2012/08/24
Journal Article
PDF
