No abstract available

No abstract available

[en] We report non-linear solutions describing the large-scale coherent motion of bubbles and spikes in the Rayleigh-Taylor and Richtmyer-Meshkov instabilities for fluids with a finite density ratio in general three-dimensional case. The non-local character of the interface dynamics is taken into account with a multiple harmonic analysis. The theory yields a non-trivial dependence of the bubble velocity and curvature on the density ratio and reveals an important qualitative distinction between the dynamics of Rayleigh-Taylor and Richtmyer-Meshkov bubbles

[en] Stability properties of the time-filtering particle codes have been investigated. The critical wavenumbers for the stability are presented as a function of the time-step for the two implicit algorithms. (author)

[en] It is shown that deflagrations supported by thermal radiation are classfied into two types, a supercritical deflagration and a subcritical one. Their characteristics and structures are investigated in the framework of the diffusion approximation for radiation flux. The subcritical deflagration is found to be easily obtained and to lead to larger compression than the supercritical one. The efficiency of compression driven by the deflagrations is estimated to be 0.1 approx. 0.3

[en] Paper presents data on the efforts to investigate into the transmutation efficiency of minor actinides in terms of the subcritical reactor core controlled by a linear accelerator (the ADS System Design). The Pb-Bi liquid eutectics is considered to serve as a coolant and as a neutron source within the system. On the basis of the numerical parametric analysis of the multiplication factor evolution and of the reactor core reactivity, as well as, on the basis of choice of Pu initial load one offers the ADS transmutation system optimal configuration

[en] In this study, the mass flow in double-strata nuclear fuel cycle is analysed based on mass inventory balance model, and the cost evaluation is carried out. As the commercial reactor fuel cycle, which is assumed to be sustainable in a significantly long term, the following different reactors and fuel cycles are considered: (1) Scheme of light water reactor (LWR-UOX and -MOX) based on sea water uranium resources, (2) Scheme of reduced-moderation water reactor (RMWR) with Pu breeding and (3) Scheme of fast breeder reactor (FBR). (author)

[en] The theoretical and computational researches on inertial confinement fusion are presented. The first topic is the reflectivity estimation due to stimulated laser scattering. Taking into account the nonlinear ion Landau damping and the enhanced linear Landau damping, the laser intensity dependent reflectivity was obtained. The results were compared with the experimental results with CO₂. The next problem is the hot electron transport. The self-consistent stationary density jump, potential jump and hot electron heat flux were obtained. The effects of anomalous resistivity and the E-field generation were investigated by using the multigroup diffusion transport code. The comparison between the theory and the computer simulation was done for the ablation structure. The mechanism of the fast ion generation was investigated, taking into account the effects of two electron temperature plasma and multi-species ions. Various computation codes were developed. EXPLOD is a code to make the experimental data replication for an exploding pusher target. The first implosion process of a double layer target was studied by using the code HIMICO. The transport of high energy electrons for the ablative mode compression was also investigated with the HIMICO. By using a two-dimensional code, two kinds of advanced targets were studied. (Kato, T.)

[en] The aim of the present study is thus to investigate how the characteristics of the thermonuclear reaction wave in the high-density plasma depend on such processes as the shock heating, the electron thermal conduction and the α-particle conduction. The ignition condition and development of a weak reaction wave which was analytically investigated are presented

[en] The Rayleigh-Taylor instability occurs at the interface between 2 fluids when a light fluid supports a heavy one in a gravitational field. We have performed 3-dimensional hydrodynamic Rayleigh-Taylor simulations with initial perturbations with two modes to clarify nonlinear dynamics of the bubbles. By imposing two modes with different initial amplitudes, well defined bubbles with three different sizes, small, medium and large, can be formed. We pay attention to the generation of not only transverse vortex, perpendicular to the gravity, but also to the generation of the longitudinal one, and to relation between the bubble dynamics and the vortex. It is pointed out that the longitudinal vortex is generated because of the existence of a pressure gradient, parallel to the gravity, caused by fluid flow stagnated at the saddle and that three different bubble velocities co-exist. This last point implies that a global non-linearity must determine the bubble evolution