J.M. Perlado

Recent results in the analysis of heavy-ion-beam-driven ICF targets☆

Abstract As a continuation of previous work on the analysis and optimization of ICF beam and target configurations, the influence of the energy deposition profi

Option for Spallation Neutron Sources

Spallation reactions are a very important option for efficient neutron sources appropriate for fusion materials testing. An “option of this option” is the EURAC concept, which makes use of short-term accelerator technology in the cheapest way and is proved to provide the needed neutron flux to verify fast experiments on fusion materials performance. Its flexible conception allows an optimum combination of very high fluxes of about 1016 n/cm2/s, with decreasing fluxes along the testing zones in enough volume to perform the correct irradiations. With this assumption, the rate effect can be perfectly analyzed together with the end-of-life conditions assumed in the structural material of the future fusion environments. The possible negative effects of the high-energy neutrons in the Spallation spectrum have been taken into account, concluding their non-significance in the desired damage parameters. The EURAC concept can also be considered in light of other purposes like incineration processes,μ production, and, with the appropriate booster, high-flux cold neutron source.

Neutronics on inertial fusion reactors

Abstract Neutrons produced in conceptual high gain targets of inertial fusion (IFE) reactors can contribute to the dynamics of the DT fuel burnup, and will emerge after some slowing down in the capsule with an energy spectrum depending on the target design and burnup conditions. Analysis of such spectra has been performed for different direct-drive target designs and ρR, and the time-dependent emission and arrival to the first wall of the system are reported. On the basis of established reactor designs (first variable to be considered) such as HIBALL-II or KOYO, the realistic possibility to obtain an uniform power distribution and obtain enough tritium breeding can be demonstrated. Activation of steels, vanadium alloys and SiC based composites has been considered in comparative analysis using different neutron energy spectra showing the important energy-dependent effect and the general advantages of V-alloys and SiC composites. The correct simulation of chains leading to radiological critical isotopes (function of neutron energy) and the goodness of nuclear data are essential for final responses/conclusions, and they need to be evaluated with careful uncertainty analysis. The damage accumulation because of very intense pulsed neutron fluxes in IFE reactors needs to be well understood prior to consideration of the availability of use of some very extensively considered low-activation materials. Results on simulations performed on SiC using an accumulated dose of 2×1014 recoi1s cm−2 are discussed and future work planned. Activation and damage analysis will impose clear boundaries in the final design of the reactor, and the availability in IFE power plants to include liquid protections to the walls is certainly very important.

Recent progress on fusion nuclear technology in inertial fusion

Abstract Inertial fusion energy (IFE) ignition and gain facilities based on lasers, the national ignition facility (NIF/USA) and the laser megajoule (LMJ/France), will be operating in the first years (2002–2010) of the next century. The conceptual design of another ignition and gain facility, the heavy ion design of ignition facility (HIDIF), is under way in an European initiative. NIFs target emission spectra show the differences in the energy fraction of debris and X-rays between direct and indirect driven (hohlraum) targets and the importance of the angular dependence in hohlraum emissions. Emerging neutrons could limit the availability to the chamber area because of activation and produce damage in the final optics; however, the NIF/LMJ designs do not envision significant effects in routine or accident conditions. Damage from debris and X-rays to the chamber wall has been extensively analyzed, concluding on the use/choice of coating materials (B4C, B, C). Removal depths in the wall/chamber have been estimated, together with the materials deposition in areas such as final optical assembly (FOA), target positioner, and debris shields. Differences in NIF and LMJ chambers include essentially the concrete shielding sandwiches in the Al layers in the case of LMJ. The use of present technology of composite materials, instead of Al, will give a better contact dose rate in some frequent access areas of the facilities. After previous reactor concepts reported in the early 90s, additional work has been done on LIBRA-SP, HYLIFE-II and KOYO designs, establishing new approaches to protection and material consideration, together with systems such as the target injector (HYLIFE-II). The choice and disposition of materials in KOYO (SiC + HT-9), LIBRA-SP (HT-9) and HYLIFE-II (SS304) is presented for handling and disposal considerations, with clear consequences in the classification of areas for shallow land burial (SLB). The importance of uncertainties in nuclear data will be discussed, and its influence in early conclusions. The effect of neutron spectrum in accidental release emissions by activation of materials is also critical in the characterization of the components of the reactor, and will be discussed.

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.

Considerations on neutron/environment characteristics in inertial fusion ignition (NIF) and reactor (KOYO) facilities

This paper reviews reported calculations on the assessment of some environmental questions related to neutron activation in ignition (National Ignition Facility, NIF) and reactor (KOYO Project) inertial fusion facilities. NIF results on the availability of the target chamber after different gain shots, inventories of activated gases in the bay area, and comments on radiological impacts from normal operations have shown the good environmental qualifications of this facility. The laser fusion conceptual reactor KOYO, developed by the ILE Osaka, uses liquid LiPb film protection flowing through ceramic SiC-base porous tubes in two different packing fraction blankets. It is shown the availability of a large fraction of the SiC with impurities to be considered as class C shallow land burial (SLB); however, the complete solution for SLB is the use of porous woven graphite (C) fabric tubes. An important effect in the activation of the chamber wall, composed by the ferritic steel HT-9, is demonstrated by using an intermediate graphite reflector. A good activation performance in the chamber is demonstrated allowing SLB and different recycling options. Hypothetical environmental releases of 1 kg of target-emissions-facing SiC tubes and HT-9 materials have also been simulated indicating optimum performances.

Heavy ion fusion research in Spain

The indirect-direct illumination scheme has been investigated, and simulations were performed using the radiation-hydrodynamics code Sara, showing good agreement with experiments performed at CEL-V Limeil (France) in the PHEBUS laser. The use of an externally guided implosion of the fuel has been suggested, where two pellets, each being accelerated from opposite mouths of a cannon barrel, will collide and implode in a central cavity. A detailed opacity model (Jimena-Dca) has been developed that treats absorption bands that result from many-particle configurations using the original Mozskowskis formalism; our average ion model (Jimena-Ai) also includes that model. Frequency-dependent opacities for intermediate- and high-Z plasmas have been computed and tested through the WORKOP series. An adaptive mesh scheme has been implemented in the two-dimensional Arwen code based on an implicit Riemann solver and part of a Lagrangian flux-corrected transport staggered-mesh (RMFCT) scheme. The code can handle several materials on a Eulerian mesh, and includes simple ion and laser energy sources. A two-dimensional code for radiation-hydrodynamics (Multi-2D) has been developed that uses non-structured triangular grids, and includes arbitrary Eulerian-Lagrangian hydrodynamics, radiation transport by discrete ordinates, and laser or heavy ion beam deposition. The inventory and radiological code ACAB has been extensively used to determine the activation in inertial fusion reactors and has been improved to include pulsed regimes and fission process. A molecular dynamics code has been developed in collaboration with LLNL to study neutron damage in SiC. DENIM is actively participating as one of the main proponents of the European Heavy Ion Ignition Facility of the European authorities, together with GSI Darmstadt, ENEA Frascatti and KfK Karlsruhe.

High-Gain Direct-Drive Target Design for ICF

The study of the efficiency of high-gain direct-drive targets for ICF has been increased during last years because of the significant progress achieved in laser experiments. Two major key issues have been observed. First, main advances on the uniform illumination to implode targets, due to the techniques developed at NRL1, Rochester2 and Osaka3. Second, lower growth rates for the hydrodynamic instabilitites up to a 30% of the clasical value by using short wavelength lasers.

Inertial fusion activities in Spain

Abstract A method is proposed to exploit the aneutronic p- 11 B fusion reaction by means of igniting a heat detonation wave that expands across the fuel from a small heated region. The tritium seeding effect of DT, 6 LiD, 7 LiD, p 11 B, 10 BD, 3 HeD fuels has been analysed, showing that the impact of initial tritium is not so important in aneutronic reactions. The 2D ARWEN code includes a flux limited multigroup radiation diffusion solver with grey acceleration, which is being used to design and analyse X-ray driven experiments on Richtmyer–Meshkov instability, and on jet production with conical hollow charges. Shock wave propagation experiments, using Al foils, performed at LULI have been analysed using simulations with the SARA-1D multigroup radiation code. A small level of preheating caused by the absorption of X-rays with energies close to the K-edge of aluminium has been shown. Integrated simulations of NIF-type hohlraum targets based on latest revision of MULTI2D are presented. A new model for the Rayleigh–Taylor instability of steady ablation fronts which overcomes past inconsistencies and reproduces a wide set of reported results has been developed. DENIMs LTE and non-LTE atomic physics codes, JIMENA, ANALOP, CARMEN, and M3R, have been compared with others codes and with recent available experiments. Results reviewed here have been presented in the Workshop on Kinetic NLTE codes held in August 1996, and the WORKOP-IV for LTE plasmas held in Madrid May 1997. New capabilities in the inventory ACAB code are: (i)xa0pulsed irradiation, applied to NIF scenario; (ii)xa0capability to estimate the effect of the cross-sections uncertainties in the accuracy of activation calculations, applied to study the long-term activation of natural elements, with neutron spectrum from HYLIFE-II vessel; (iii)xa0sequential charged-particle reactions, analysing the effect in the activation of Flibe, under a HYLIFE-II scenario for maintenance and decommissioning purposes. Analysis of deep penetrations in the KOYO reactor, affecting damage of final optics, has been performed. Irradiation damage of high-Z materials, using Molecular Dynamics and Defect Kinetic MonteCarlo Diffusion models, has been studied in a microscopic base. New reviewed results are being produced for primary damage parameters of SiC, as low activation material, and first calculations on basic metals to be extended to binary/ternary alloys (steels).