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Languages : en
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For heavy-ion beam driven inertial fusion ''liquid-protected'' reactor designs such as HYLIFE-II, a mixture of molten salts made of F[sup 10], Li[sup -6], Li[sup 7] and Be[sup 9] (called flibe) allows small chambers and final-focus magnets closer to the target with superconducting coils suffering higher radiation damage, though they can stand only a certain amount of energy deposited before quenching. This work has been primarily focusing on verifying that total energy deposited by fusion neutrons and induced gamma rays remain under such limit values and the final purpose is the optimization of the shielding of the magnetic lens system from the points of view of the geometrical configuration and of the physical nature of the materials adopted. The system is analyzed in terms of six geometrical models going from simplified up to much more realistic representations of a system of 192 beam lines, each focused by six magnets. A 3-D transport calculation of the radiation penetrating through ducts, that takes into account the complexity of the system, requires Monte Carlo methods. The quantities analyzed, using the two codes MCNP and TART include: neutron mean free path and total path length dependence on energy, energy deposited by neutrons and gamma photons, values of the total fluence integrated in the whole energy range, and the neutron spectrum in different zones of the system. The technical nature of the design problem and the methodology followed were presented in a previous paper by summarizing briefly the results for the deposited energy distribution on the six focal magnets. Now a much more extensive comparison of the performances of the two codes for different configurations of the system is discussed, separating the n and [gamma] contributions, in the light of the physical interpretation of the results in terms of first flight and of scattered neutron fluxes, of primary [gamma] and of secondary [gamma] generated by inelastically scattered or radiatively captured neutrons. The final conclusions indicate some guidelines and suggest possible improvements for the future neutronic design of a heavy ion beam fusion facility named IRE (Integrated Research Experiment) to be realized in the US.
Author: Dandan Zheng
Publisher:
ISBN:
Category :
Languages : en
Pages : 474
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Author: Timothy Eugene Valentine
Publisher:
ISBN:
Category : Criticality (Nuclear engineering)
Languages : en
Pages : 288
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Author:
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Category :
Languages : en
Pages :
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The shielding for 14-MeV neutrons from a D-T generator at SLAC needs to be optimized in terms of shield thickness and cost. Shielding calculations were made using the MCNP4B Monte Carlo code and the ENDF/B-VI cross section set. A few materials were studied: iron, borated polyethylene, three types of normal and heavy concrete, and mixtures of iron and borated polyethylene. The effects of shielding geometry (sphere, cube, and the proposed geometry) were also examined. The transmission results of ambient dose equivalents, as well as the attenuation lengths and the average energies, for neutrons and gammas outside the shielding are presented.
Author: F. H. Clark
Publisher:
ISBN:
Category :
Languages : en
Pages : 19
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An extensive program of calculations was performed to check certain fast-neutron dose-rate measurements made at Project BREN in 1962. The response characteristic of the modified long counter was computed. Nitrogen and oxygen cross sections were reviewed and used in calculations of the transport in air of neutrons from a Godiva source to a distance of 66 g/sq cm. Transport results obtained by Monte Carlo were compared with those obtained by the moments method. A spectrum at an 80-g/sq cm penetration was determined. The perturbating effect of a structure on the neutron field in its neighborhood was estimated. The effect of variations of the spectrum with penetration distances on doses computed with different weight functions was also examined; the Snyder-Neufeld multicollision physical dose was found to vary with distance in a way markedly different from others examined. Work was also done on importance sampling techniques, especially the exponential transform, and the sampling problem was formulated in a simplified, approximate expression to facilitate statistical interpretations. Finally, a number of shield penetration calculations were performed to compare with the measurements and to determine the effects of shield shape, shield cavity size, and source angular distributions incident on the shields. The agreement between the calculations and the measurements was within the uncertainty in the detector response characteristic. (Author).
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Category :
Languages : en
Pages :
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MCNP is a very general Monte Carlo neutron photon transport code system with approximately 250 person years of Group X-6 code development invested. It is extremely portable, user-oriented, and a true production code as it is used about 60 Cray hours per month by about 150 Los Alamos users. It has as its data base the best cross-section evaluations available. MCNP contains state-of-the-art traditional and adaptive Monte Carlo techniques to be applied to the solution of an ever-increasing number of problems. Excellent user-oriented documentation is available for all facets of the MCNP code system. Many useful and important variants of MCNP exist for special applications. The Radiation Shielding Information Center (RSIC) in Oak Ridge, Tennessee is the contact point for worldwide MCNP code and documentation distribution. A much improved MCNP Version 3A will be available in the fall of 1985, along with new and improved documentation. Future directions in MCNP development will change the meaning of MCNP to Monte Carlo N Particle where N particle varieties will be transported.
Author: Carsten Ullrich
Publisher: Oxford University Press
ISBN: 0199563020
Category : Science
Languages : en
Pages : 541
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Time-dependent density-functional theory (TDDFT) is a quantum mechanical approach for the dynamical properties of electrons in matter. It's widely used in (bio)chemistry and physics to calculate molecular excitation energies and optical properties of materials. This is the first graduate-level text on the formal framework and applications of TDDFT.
Author: William Kruer
Publisher: CRC Press
ISBN: 1000754464
Category : Science
Languages : en
Pages : 176
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This book focuses on the physics of laser plasma interactions and presents a complementary and very useful numerical model of plasmas. It describes the linear theory of light wave propagation in plasmas, including linear mode conversion into plasma waves and collisional damping.
Author: United States. General Accounting Office
Publisher:
ISBN:
Category : Nuclear power plants
Languages : en
Pages : 16
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Author: Karl Verfondern
Publisher: Forschungszentrum Jülich
ISBN: 3893364684
Category : Hydrogen
Languages : en
Pages : 199
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