A numerical simulation was undertaken on argon and krypton isotope separation in their dc arc discharges through a thin capillary. The mass transport phenomenon of neutral particles as well as of ions in the positive column was treated by direct simulation Monte Carlo method, whereas electrons were treated as background particles, and their behavior was assumed to be already given to evaluate the effects of electron collisions onto neutral particles. The numerical results agreed qualitatively with the isotope separation phenomena of argon and krypton dc discharges. The heavier isotopes were enriched into the region of the cathode, whereas the lighter ones into that of the anode. It was also found that the numerical results explained the pressure difference between the cathode and the anode observed experimentally. The characteristics of drift motion of ions also qualitatively agreed with existing experimental results.

This paper discusses a rational methodology to evaluate dose rate at the boundary of the interim storage facility using two methods; 1) a method taking into account``shade eŠect'' which represents the self-shielding eŠect of interim storage containers, 2) utilization of a newly developed simpliˆed code. It was proved that the method of the shade eŠect is applicable to the secondary gamma-ray, which dominates approximately 50 of the total eŠective dose rate. Thus, the eŠective dose rate attributed to the secondary gamma-ray depends on both the number of containers in the facility and the shade coe‹cient which represents the factor of the shade eŠect. Using this shade coe‹cient, the dose rate was estimated for the facility that stored 8 or 16 containers around the boundary of the facility and the results were consistent with that of the Monte Carlo calculation. In the present study, a simple neutron transport code, MCNP-ANISN_W, was newly developed aiming at the simpliˆcation of large-scale calculation. The results of the dose rate agreed well with that of the Monte Carlo calculation. The results of the present study show that the simple evaluation technique and the code developed in this study would be useful for the evaluation of dose rate around the boundary of the interim storage facility.

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In general, computational fluid dynamics (CFD) models incur high computational costs when dealing with realistic and complicated flows. In contrast, the mass-consistent flow (MASCON) field model provides a three-dimensional flow field at reasonable computational cost. Unfortunately, some weaknesses in simulating the flow of the wake zone exist because the momentum equations are not considered in the MASCON field model. In the present study, a new set of improved algebraic models to provide initial flow fields for the MASCON field model are proposed to overcome these weaknesses by considering the effect of momentum diffusion in the wake zone. Specifically, these models for the wake region are developed on the basis of the wake models used in well-recognized Gaussian plume models, ADMS-build and PRIME. The MASCON fields provided by the new set of wake zone models are evaluated against wind-tunnel experimental data on flow around a wall-mounted rectangular obstacle. Each MASCON field is compared with the experimental results, focusing on the positions of the vortex core and saddle points of the vortex formed in the near-wake zone and the vertical velocity distribution in the far-wake zone. The set of wake zone models developed in the present study better reproduce the experimental results in both the wake zones compared to the previously proposed models. In particular, the complicated recirculation flow which is formed by the union of the sidewall recirculation zone and the near-wake zone is reproduced by the present wake zone model using the PRIME model that includes the parameterization of the sidewall recirculation zones.