Doppler broadening of neutron-induced resonances using ab initio phonon spectrum

CONRAD – a code for nuclear data modeling and evaluation

“…In the past few years, fission yields models [5,6], prompt fission neutron spectrum and multiplicities based on Madland-Nix model (see Sect. 2.5.4 for an example), thermal data models [7] and delayed neutron data models used in evaluation [8] were implemented. Further details on the results can be found in the related papers.…”

“…The major part of the recent experimental developments were related to the enhancement of these capabilities. In particular, Doppler broadening (from a Free-Gas Model to a Crystal Lattice Model [7]) to take into account better temperature effects (especially at low temperature), experimental apparatus resolution function (from simple analytic forms to user-provided tabulated functions), detector efficiency uncertainties, resonant scattering (to treat properly large targets) [14] and a lot of target corrections such as in-homogeneous material and porosity were proposed [4,15]. Furthermore, the possibility of using integral data measurements during the nuclear data evaluation was provided, for multigroup cross-section adjustments (see [16]) as well as for nuclear reaction model parameters (see [17]).…”

“…1) opens the range of various additional nuclear data analysis. So far, the following models were also implemented or interfaced: -models for thermal data calculation [7]; -DPA cross sections models [44]; -expression-based model: description given with standard mathematical functions in the input file.…”

Combining density functional theory and Monte Carlo neutron transport calculations to study the phonon density of states of UO2 up to 1675 K by inelastic neutron scattering

“…The highest energy structures are dominated by the optical phonon modes of the oxygen atoms. For comparison, the PDOS calculated at Uppsala University for T = 294 K [8] is shown in the same figure. The principle of the calculations performed in the quasiharmonic approximation is reported in Refs.…”

“…1. Ab initio phonon density of states of UO 2 at T = 0 K [6] and T = 294 K [8]. The dot-dashed lines locate the main vibration modes of UO 2 calculated at T = 294 K. The two first peaks at 10 and 20 meV correspond to the translational (TA) and longitudinal (LA) acoustic phonon modes of the uranium atoms.…”