Neutron Nuclear Data Evaluation of Cesium Isotopes for JENDL-4.0

概要

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For the development of JENDL-4.0, neutron nuclear data for fission product nuclides, 133,134,135,136,137Cs, were revised in the incident neutron energy range from 1 eV to 20 MeV by using a coupled-channels optical model (OM), and nuclear reaction models. The OM potential parameters were determined for stable 133Cs to reproduce the experimental data of total and elastic scattering cross sections and angular distributions of elastically scattered neutrons. The present results reasonably reproduce measured data for (n,2n), (n,p), (n,α), and capture reactions on 133Cs. Important differences between the present results and JENDL-3.3 are found for the capture cross sections of 134,137Cs. The cross section obtained for 137Cs was smaller than that in JENDL-3.3. This result makes the transmutation of medium-lived 137Cs increasingly difficult. The production probabilities of metastable states for 134,138Cs via capture reactions on 133,137Cs are compared with experimental values. The present result for 134mCs production is marginally consistent with measured data. However, a large discrepancy is recognized for 138mCs production. The γ-ray emission data were evaluated with available measurements, and newly compiled in JENDL-4.0. Maxwellian-averaged capture cross sections were calculated in the energy range from 1 to 103 keV, and are compared with other derived data.
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