Importance of the neutron flux information to the evaluation of thermal neutron capture cross section and resonance integral of minor actinides

Mizuyama, Kazuhito; Iwamoto, Nobuyuki  ; Iwamoto, Osamu  

The accurate data of the minor actinides (MAs) is required for the nuclear waste problem. However, there is large discrepancy among the previous data. Especially such large discrepancy can been seen between the activation and the time-of-flight measurements. In the activation measurements, the Cd-ratio method based on the Westcott convention has been used in order to obtain the thermal neutron capture cross section and the resonance integral or the s-factor . By reviewing the Westcott convention and the Cd-ratio method, we found that the large discrepancy of can be made smaller by introducing a correction term for the resonance integral or the s-factor in order to correct the contribution of the resonances near the Cd cut-off energy. However, the discrepancy of the resonance integral and the s-factor still remains. In the original Westcott convention, the epithermal component of the neutron flux has been supposed to be proportional to , but it may not be true in the realistic condition of the neutron flux. Supposing for the epithermal component, we found that dependence is not negligible. For the fully consistent and more accurate evaluation of the previous activation measurements for MAs, the detailed information of the neutron flux is necessary and very important.