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

Abstract

Cross sections for neutron interactions with 238 U in the energy region from 5 keV to 150 keV have been evaluated. Average total and capture cross sections have been derived from a least squares analysis using experimental data reported in the literature. The resulting cross sections have been parameterised in terms of average resonance parameters maintaining full consistency with results of optical model calculations by using a dispersive coupled channel optical model potential. The average compound partial cross sections have been expressed in terms of transmission coefficients by applying the Hauser-Feshbach statistical reaction theory including width-fluctuations. A generalized single-level representation compatible with the energy-dependent options of the ENDF-6 format has been applied using standard boundary conditions. The results have been transferred into a full ENDF-6 compatible data file.

Critical review of CIELO evaluations of n+ 235U, 238U using differential experiments

“…IAEA CIELO 238 U (n,g) cross sections were adopted from Neutron Standards fit [19] and are shown in Figure 4b compared to evaluated JEFF-3.3 cross section. Evaluated reference 238 U (n,g) cross sections within the Neutron Standards are in excellent agreement with newest highaccuracy measurement at JRC Geel [32,33], while the evaluated JEFF-3.3 cross sections are lower in the whole energy range. The difference between both evaluations reaches about 7% around 45 keV.…”

Note on the potential to increase the accuracy of source term calculations for spent nuclear fuel

“…An important precondition is the correct determination of the sample burnup. However, for large-scale fuel assembly loading and preparation for final storage use of burnup (Sirakov et al, 2017) relevant for criticality, burnup credit and dose rate (primary decay modes in yellow: α; black: stable; blue: β -).…”

“…Also, newer evaluations of nuclear data do not necessarily lead to higher quality. In (Sirakov et al, 2017) the cross section for 238 U (n,γ) in JEF-2.2 were compared with the JEFF-3.3 recommendations. New measurements showed better agreement with JEF-2.2.…”

“…FIGURE 4Nuclides of interest identified in (IAEA -TECDOC -1241, 2001),(Sirakov et al, 2017) relevant for criticality, burnup credit and dose rate (primary decay modes in yellow: α; black: stable; blue: β -).…”

Nuclear data activities at GELINA

“…[29]) and the neutron standards projects [22]. Recent evaluations largely based on data from GELINA are: 107,109 Ag [13], 99 Tc [30], 241 Am [31], 238 U [32], 197 Au [14,22], 16 O(n,) [33], 175 Lu [34] and Mo [12].…”