High-Resolution Study of 237Np Fission Cross Section from 5 eV to 1 MeV

W. Furman
2005 AIP Conference Proceedings  
A series of measurements of 237 Np fission cross section have been performed at the CERN spallation neutron facility n_TOF which covers a wide energy range from 1 eV up to 250 MeV. A fast ionization chamber (FIC) was used as a fission fragment detector with registration efficiency of not less than 97 %. Particular attention was paid to correct the fission Physics 0-7354-0254-X/05/$22.50 cross section with use of 235 U standard. Total experimental uncertainties are determined to be at the level
more » ... to be at the level of 3%. Analysis of the experimental data in the restricted neutron energy from 5 eV up to 1 MeV showed a systematic deviation from evaluated data (ENDF/B-VI). This discrepancy amounts to up to a factor 3 for resolved resonances in the neutron energy range of 5 eV -2 KeV, and is in good agreement with some previous experiments. A similar disagreement at the level of 6-7% was found for higher energies around the threshold (E n = 300 keV-1 MeV). This energy range is essential for the transmutation of neptunium in ADS or fast reactors. It is concluded that an updated evaluation of nuclear data for 237 Np is required.
doi:10.1063/1.1945184 fatcat:uoxc2puzcjaljg2givy4cvx32e