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[en] The critical slab problem has been studied in the one-speed neutron transport equation with isotropic scattering by using the first kind of Chebyshev Polynomials. The moment criticality solutions were obtained for the uniform finite slab using Mark and Marshak type vacuum boundary conditions. The results obtained by this approximation are presented in tables which also include the results obtained by the PN method for comparison. (orig.)
[en] Investigating and modelling pedestrian flows in underground stations is essential to improve criteria in stations designing and in order to manage ordinary and critical situations, simulating the human behaviour in such situations.
[it]Esaminare e modellare le dinamiche dei flussi di persone all'interno delle stazioni della metropolitana e fondamentale per elaborare nuovi criteri di sicurezza per la progettazione delle stazioni, e per la gestione delle situazioni ordinarie e critiche.
[en] The probability table representation of cross-sections is generally used to deal with neutron interactions in the unresolved energy range. In the frame of neutron transport methods, the capability of the probability table representation of cross-sections on the whole neutron energy range has been mentioned by and it has been already demonstrated for the Monte Carlo transport calculations by . Such an advantage is also illustrated here with a simple neutron propagation configuration dealt with the TRIPOLI-4 Monte Carlo transport code. This article gives a new expression of the integral operator kernels for adjoint Monte Carlo neutron multigroup transport including the probability table representation of cross-sections. This formalism is applied to the adjoint two energy group neutron transport in an infinite homogeneous medium. Therefore, the same physical advantage as in forward neutron transport should be expected for adjoint neutron transport.
[en] The accurate, detailed and 3D neutron transport analysis for Gen-IV reactors is still time-consuming regardless of advanced computational hardware available in developed countries. This paper introduces a new concept in addressing the computational time while persevering the detailed and accurate modeling; a specifically designed FPGA co-processor accelerates robust AGENT methodology for complex reactor geometries. For the first time this approach is applied to accelerate the neutronics analysis. The AGENT methodology solves neutron transport equation using the method of characteristics. The AGENT methodology performance was carefully analyzed before the hardware design based on the FPGA co-processor was adopted. The most time-consuming kernel part is then transplanted into the FPGA co-processor. The FPGA co-processor is designed with data flow-driven non von-Neumann architecture and has much higher efficiency than the conventional computer architecture. Details of the FPGA co-processor design are introduced and the design is benchmarked using two different examples. The advanced chip architecture helps the FPGA co-processor obtaining more than 20 times speed up with its working frequency much lower than the CPU frequency. (authors)
[en] The Chebyshev polynomial approximation is used to solve the reflected critical slab problem for one-speed neutrons in a slab with strongly anisotropic scattering. The scattering kernel which is a combination of backward-forward-isotropic scattering and linearly anisotropic scattering is chosen in a uniform finite slab. The critical slab thicknesses are given for different degrees of reflection, backward-forward and linear anisotropy. Calculated numerical results for the critical thickness are in good agreement with the results available in literature. (orig.)
[en] The details about how to use MCNP to solve multigroup transport problem is introduced. Some critical and fixed source cases are calculated by using MCNP, the results are in good agreement with the reference values. The successful application of MCNP has important significance, it not only provides a new way to solve multigroup neutron transport equation, but also provides an effective checking tool for developing new multigroup transport calculation codes. (authors)
[en] The one speed, time independent neutron transport equation for slab geometry with quadratic anisotropic scattering kernel is considered. Albedo, transmission factor and criticality thickness are calculated by the HN method. The numerical results obtained are listed for different selected parameters. It is shown that the method is concise and leads to fast converging numerical results. (orig.)
[en] In this work, the HN approximation is used to solve the Milne problem for both isotropic and linearly anisotropic scattering. For different specular and diffuse reflection coefficients the extrapolated endpoint is calculated. The numerical results obtained are compared with results already existing in the literature. It is shown that they are in good agreement. (orig.)
[en] In the Langevin description of Brownian motion, the action of the surrounding medium upon the Brownian particle is split up into a systematic friction force of Stokes type and a randomly fluctuating force, alternatively termed noise. That simple description accounts for several basic features of particle transport in a medium, making it attractive to teach at the undergraduate level, but its range of applicability is limited. The limitation is illustrated here by showing that the Langevin description fails to account realistically for the transport of a charged particle in a medium under crossed electric and magnetic fields and the ensuing Hall effect. That particular failure is rooted in the concept of the friction force rather than in the accompanying random force. It is then shown that the framework of kinetic theory offers a better account of the Hall effect. It is concluded that the Langevin description is nothing but an extension of Drude's transport model subsuming diffusion, and so it inherits basic limitations from that model. This paper thus describes the interrelationship of the Langevin approach, the Drude model and kinetic theory, in a specific transport problem of physical interest