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Accurate knowledge of the single-molecule (self-) translational dynamics of liquid para-${\mathrm{H}}_{2}$ is an essential requirement for the calculation of the neutron scattering properties of this important quantum liquid. We show that, by using centroid molecular dynamics (CMD) quantum simulations of the velocity autocorrelation function, calculations of the total neutron cross section (TCS) remarkably agree with experimental data at the thermal and epithermal incident neutron energies where para-${\mathrm{H}}_{2}$ dynamics is actually dominated by the self-contributions. This result shows that a proper account of the quantum nature of the fluid, as provided by CMD, is a necessary and very effective condition to obtain the correct absolute-scale cross section values without the need of introducing any empirically adjusted quantity. At subthermal incident energies, appropriate modeling of the para-${\mathrm{H}}_{2}$ intermolecular (distinct) dynamics also becomes crucial, but quantum simulations are not yet able to cope with it. Existing simple models which account for the distinct part provide an appropriate correction of self-only calculations and bring the computed results in reasonable accord with TCS experimental data available until very recently. However, if just published cross section measurements in the cold range are considered, the agreement turns out to be by far superior and very satisfactory. The possible origin of slight residual differences will be commented on and suggests further computational and experimental efforts. Nonetheless, the ability to reproduce the total cross section in the wide range between 1 and 900 meV represents an encouraging and important validation step of the CMD method and of the present simple algorithm.

Nuclear fuel plates based on a γU-Mo/Al mixture are proposed for research reactors. In this work their thermal behavior in the [425; 550°C] temperature range has been studied mainly by neutron and high energy X-ray diffraction. Even if complementary studies will be necessary, the kinetics of first the growth of the interaction layer between γU-Mo and Al and second of the γU-Mo destabilization have been accurately measured. This basic work should be helpful for defining manufacturing conditions for fuel plates with optimized composition.

International audience; The aim of this work is to validate experimentally the results of the Monte Carlo Recoil Energy Determination (MC-RED) nuclear physics code used to determine the deposited energy in a silicon volume taking into account the probabilistic approach of the physical phenomenon. A silicon sensor has been used to measure the deposited energy spectrum after an irradiation with a 14 MeV neutron source. Neutrons of 14 MeV were produced by the SAMES accelerator of the Valduc CEA research center. The experimental results were compared with the one obtained by the MC-RED code in the same silicon volume. To compare experiment and simulations, it requires that the complete neutron field be specified. We have to take into account the facility cell environment. Nuclear simulations were performed with the MCNP code to determine with accuracy the energy spectra of neutrons and gamma rays produced by this facility on the sensor. It is shown that the contribution of secondary neutrons is not negligible

The 'service of research on neutronics and criticality' of Valduc CEA research center, proposes several experimental facilities for neutron and gamma irradiation: two metallic reactors, a solution reactor, two accelerators.