Neutron Absorption Cross Section of Americium-241

Americium-241 phase I: reevaluation for JEFF-3.1.1 and a step forward

“…As far as the fourth resonance is concerned (see Figure 9), JEFF-3.1.1, JEF-2.2, JENDL-3.3, and the ENDF/B-VII.0 libraries as well as the present twosteps calculation are in agreement and are smaller in magnitude than Weston and Todd's [29] renormalized data. Since all theses evaluated curves are also smaller than the transmission measurement by Derrien and Lucas [37], we can say that in the ''current'' knowledge there is some room for increasing the integral value over this resonance.…”

“…Belanova et al's [21] results relative to this resonance are clearly distorted and were very weakly considered during the fit on this resonance. From these considerations, the resulting one-(JEFF-3.1.1) or present two- The agreement between the one-(JEFF-3.1.1) or present two-step fitted absorption cross sections and Weston and Todd's [29] data over the third resonance energy domain (see Figure 8) is much better because our fit is no more driven by Slaughter et al [38] but also by the transmission measurement of Derrien and Lucas [37]. The one-or two-step fitted cross sections are slightly higher than the curves reconstructed from the JENDL-3.3 and ENDF/B-VII.0 libraries and lead to a largest integral value over the third resonance.…”

“…a capture) performed in 1985 at the IRMM/Geel by Vanpraet et al [34] does not cover the energy range of the two lowest energy resonances and the first resonances observed are saturated (and so, was not considered during this work). The absorption measurement by Weston and Todd [29], which covers the energy range from 0.01 eV to 380 keV, exhibits a good energy resolution but also a pretty large background in the valleys between resonances (roughly evaluated to 15b in this work). The authors have estimated below the neutron energy of 200 meV a systematic error smaller than 1% and have announced above 1 eV a much larger systematic error (7%) including a 5% normalization uncertainty.…”

“…First category measurements are shown in Table 6 in terms of thermal capture cross section values for comparison with the absorption cross section measurement by Weston and Todd [29] who estimated an uncertainty less than 1% below 1 eV. The oldest total cross section measurement by Adamchuk et al [30] does not include any uncertainty.…”

“…The resonance energy is a free variable parameter which is finally fitted on our reference measurement in terms of energy scale (Dabbs et al [39]). [29] data in the neighborhood of the third resonance. The resonance energy is a free variable parameter which is finally fitted on our reference measurement in terms of energy scale (Dabbs et al [39]).…”