M. Salvador

Advances in implosion physics, alternative targets design, and neutron effects on heavy ion fusion reactors

The coupling of a new radiation transport (RT) solver with an existing multimaterial fluid dynamics code (ARWEN) using Adaptive Mesh Refinement named DAFNE, has been completed. In addition, improvements were made to ARWEN in order to work properly with the RT code, and to make it user-friendlier, including new treatment of Equations of State, and graphical tools for visualization. The evaluation of the code has been performed, comparing it with other existing RT codes (including the one used in DAFNE, but in the single-grid version). These comparisons consist in problems with real input parameters (mainly opacities and geometry parameters). Important advances in Atomic Physics, Opacity calculations and NLTE atomic physics calculations, with participation in significant experiments in this area, have been obtained. Early published calculations showed that a DTx fuel with a small tritium initial content (x<3%) could work in a catalytic regime in Inertial Fusion Targets, at very high burning temperatures (⪢100 keV). Otherwise, the cross-section of DT remains much higher than that of DD and no internal breeding of tritium can take place. Improvements in the calculation model allow to properly simulate the effect of inverse Compton scattering which tends to lower Te and to enhance radiation losses, reducing the plasma temperature, Ti. The neutron activation of all natural elements in First Structural Wall (FSW) component of an Inertial Fusion Energy (IFE) reactor for waste management, and the analysis of activation of target debris in NIF-type facilities has been completed. Using an original efficient modeling for pulse activation, the FSW behavior in inertial fusion has been studied. A radiological dose library coupled to the ACAB code is being generated for assessing impact of environmental releases, and atmospheric dispersion analysis from HIF reactors indicate the uncertainty in tritium release parameters. The first recognition of recombination barriers in SiC, modify the understanding of the calculation of displacement per atom, dpa, to quantify the collisional damage. An important analysis has been the confirmation, using Molecular Dynamics (MD) with an astonishing agreement, of the experimental evidence of low-temperature amorphization by damage accumulation in SiC, which could modify extensively its viability as a candidate material for IFE (fusion in general) applications. The radiation damage pulse effect has also been assessed using MD and Kinetic Monte Carlo diffusion of defects, showing the dose and driver frequency dependences.

Time-dependent neutronics in structural materials of inertial fusion reactors and simulation of defect accumulation in pulsed Fe and SiC

New results are presented on the time-dependent neutron intensities and energy spectra from compressed inertial fusion energy (IFE) targets and in structural Fe walls behind typical IFE chamber protection schemes. Protection schemes of LiPb and Flibe have been considered with two different thicknesses, and neutron fluxes in the outer Fe layer as a function of the time from target emission are given. Differences between the two solutions are noted and explained, and the effect of thickness is quantitatively shown. Time-dependent defect characterization of the Fe layer under pulse irradiation is presented. A new well-established multiscale modeling procedure injects, at the appropriate dose rate, damage cascades in a kinetic Monte Carlo lattice (microscopic) to study defect diffusion, clustering, and disintegration. The differences with a continuous irradiation for a still low fluence of irradiation are presented. Experimental validation of a multiscale modeling approach has been recognized and proposed in the Spanish VENUS-II project by using Fe ions on pure and ultrapure Fe. To study similar problems in SiC, new tools are needed to quantify the kinetic defects; results leading to the validation of a new tight binding molecular dynamics code for SiC are presented.

Recent theoretical and experimental results on inertial fusion energy physics

We study with ARWEN code a target design for ICF based on jet production. ARWEN is 2D Adaptive Mesh Refinement fluid dynamic and multigroup radiation transport. We are designing, by using also ARWEN, a target for laboratory simulation of astrophysical phenomena. We feature an experimental device to reproduce collisions of two shock waves, scaled to roughly represent cosmic supernova remnants. ANALOP code uses parametric potentials fitting to self-consistent potentials, it includes temperature and density effects by linearized Debye-Huckel and it treats excited configurations and H+He-like lines. Other is an average SHM using the parametric potentials above described. H-like emissivities and opacities have been simulated, using both, for Al and F plasmas with density 1023 cm-3 and temperatures higher than 200 eV. Advanced fusion cycles, as the aneutronic proton-boron 11 reaction, require very high ignition temperatures. Plasma conditions for a fusion-burning wave to propagate at such temperatures are rather extreme and complex, because of the overlapping effects of the main energy transport mechanisms. Calculations on the most appropriate ICF regimes for this purpose are presented. A new Monte Carlo procedure estimates effect of activation cross section uncertainties in the accuracy of inventory calculations, based on simultaneous random sampling of all the cross sections; it is implemented in activation code ACAB. We apply, with LLNL, to NIF gunite chamber shielding with reference pulsing operation. Preliminary results show that the 95 percentile of the distribution of the relative error of the contact dose rate can take values up to 1.2. Model is promising for uncertainty analysis of pulsed activation in IFE PP by using a continuous-pulsed model. Neutron intensities versus time after target emission are presented for IFE protections: LiPb/Flibe, including spectral effects. HT evaluation indicates that 90-98% of the total dose comes from ingestion of agriculture and meat, and the rest from inhalation by re-emission. A multiscale modeling (MM) study of pulse irradiation in Fe is presented up to microscopy; we give differences with continuous irradiation. Experimental validation of MM, using Fe+ in Fe, is being performed under VENUS II Spanish project with CIEMAT. Multiscale Modeling of SiC is reported; new defects energetic emerge using a new tight-binding molecular dynamics which has been proved in basic crystal parameters.

Insight into the materials choice for inertial fusion energy reactors considering radiation damage: Neutron irradiation intensities and basic knowledge from multiscale modeling

A review of structural materials choices under irradiation in fusion environments is presented. Results on the neutron source term and the intensities in the structural materials as a function of pulse time, energy, and protection is given. The role of multiscale modeling for understanding the basic physics in irradiated materials is explained, and simulations of metals under pulse irradiation and SiC are reported.