IAEA CIELO Evaluation of Neutron-induced Reactions on 235 U and 238 U Targets

Evaluation of cross sections for neutron interactions with 238U in the energy region between 5 keV and 150 keV

“…4 can be confirmed by comparing the experimental capture cross section ratio R = 238 U(n, γ)/ 235 U(n, γ) obtained by Wallner et al [60] for an average energy of ∼ 25.3 keV with the one derived from the CIELO(IAEA) and JEFF-3.3T4 files. Using the energy distribution reported in the EXFOR data library, a ratio of R CIELO = 0.57 is obtained from the CIELO(IAEA) file [13,15]. This ratio is within the uncertainty in agreement with the experimental value of R exp = 0.60 ± 0.03 [60].…”

“…The small average unresolved fission cross section of the order of 0.1 mb was adopted from an estimation by Trkov [51]. This estimation, which results in a more reasonable trend at the URR boundaries [13], was based on available low-resolution sub-threshold fission cross section data, particularly those of Slovacek et al [52]. [47], Litvinsky et al [48] and Moxon et al [49] are compared with the cross section calculated with and without accounting for the interference between the contributions of the direct-and of the compound reaction model.…”

“…The second version has ultimately been chosen for the final evaluation. The file produced in this work is taken over in the CIELO file that is produced at the IAEA [13], referred to as CIELO(IAEA), and adopted in ENDF/B-VIII.0 [54]. However, it was not considered for the latest version of the JEFF project, which is referred to as JEFF-3.3T4 [55].…”

“…[48,58]. Calculated spectrum averaged cross sections were derived by combining the data in table 2 with the cross section taken from the CIELO project for energies below 20 keV and above 150 keV [13]. The neutron energy distributions were obtained from calculations that were validated by results of experiments with a hydrogen proportional counter [59].…”

“…The results of the present work have been included in the evaluated data file for neutron induced reactions on 238 U reported by Capote et al [13]. The file was developed at the IAEA as part of the CIELO (Collaborative International Evaluated Library Organization) project [14,15].…”