952 research outputs found
Neutronics methods for the multiphysics analysis of nuclear fission systems
No full textThe accurate representation of the overall behaviour of advanced nuclear fission systems, including both nuclear reactors and accelerator-driven subcritical systems, typically requires to account for the interactions among the various physical phenomena that occur in the complex system comprised by a nuclear reactor. Correspondingly, the numerical codes that are intended for application to the design and the analyses of such systems are required to couple individual physics models, perhaps most notably those for neutronics and thermal-hydraulics, as these two phenomena are of great importance for safety considerations. The doctoral research activity involves the development of physical models and mathematical methods for spatial-temporal analyses of neutronics that are appropriate for use in the context of multiphysics analyses of nuclear reactor dynamics. The activity is carried out through the management, the development and the application of a multiphysics reactor analysis code, the Fast REactor NEutronics/Thermal-hydraulICs (FRENETIC) code, developed at Politecnico di Torino. First, for questions related to the practicality of the execution of spatial kinetics analyses, the quasi-static method is formulated and methods of solution of the resulting systems of equations are developed and characterised. Next, as the accuracy and the efficiency of the quasi-static approach depend on the use of proper time steps, an automatic, adaptive time step selection methodology for the quasi-static method is developed and studied. Additionally, as the effects of photon energy deposition lead to non-negligible effects on the spatial-temporal behaviour of the power in a nuclear reactor, a methodology for coupled neutron-photon dynamics appropriate for use in spatial kinetics analyses is developed and assessed. Finally, with these models and methods implemented in the FRENETIC code, the first coupled neutronic/thermal-hydraulic validation of the FRENETIC code is performed against experimental data from a formerly operating sodium-cooled fast reactor
New aspects in the implementation of the quasi-static method for the solution of neutron diffusion problems in the framework of a nodal method
No full textThe ability to accurately model the dynamic behaviour of the neutron distribution in a nuclear system is a
fundamental aspect of reactor design and safety assessment. Due to the heavy computational burden
associated to the direct time inversion of the full model, the quasi-static method has become a standard
approach to the numerical solution of the nuclear reactor dynamic equations on the full phase space. The
present paper is opened by an introductory critical review of the basics of the quasi-static scheme for the
general neutron kinetic problem. Afterwards, the implementation of the quasi-static method in the context
of a three-dimensional nodal diffusion theory model in hexagonal-z geometry is described, including
some peculiar aspects of the adjoint nodal equations and the explicit formulation of the quasi-static nodal
equations. The presentation includes the discussion of different formulations of the quasi-static technique.
The results presented illustrate the features of the various formulations, highlighting the corresponding
advantages and drawbacks. An adaptive procedure for the selection of the time interval
between shape recalculations is also presented, showing its usefulness in practical applications
Adaptive time step selection in the quasi-static methods of nuclear reactor dynamics
No full textOf the methods available by which to integrate the neutron and delayed neutron precursor balance equations in time, at present the quasi-static methods are among the most practical and favourable. However, the correct application of the quasi-static method requires the use of appropriately determined time steps, for both the reasons of accuracy and efficiency. This work presents a methodology for the adaptive selection of the time steps employed by the quasi-static method, thereby allowing the quasi-static approach to be applied in an efficient manner while maintaining a prescribed level of accuracy. The method is applied to and studied using some numeric test problems
Models and methods for the representation of decay and photon heat in spatial kinetics calculations
No full textIn nuclear fission systems, the primary contribution to the reactor power originates from the deposition of the kinetic energy of the fission fragments in the fissioning medium. Secondary, although not necessarily negligible, contributions to the reactor power arise from additional physical phenomena, including, but not limited to, the interactions of the radiation emitted in the radioactive decay of the fission products, as well as the prompt neutrons and photons produced in the fission event. The additional characteristics of the behaviour of the power due to these phenomena may be important to consider in design and safety studies, motivating their proper treatment in the numerical codes foreseen to be applied to such analyses. This work examines modelling and computational aspects of the effects of decay and photon heat in the context of space-time nuclear reactor dynamics calculation
From Foucauldian Biopower to Energopower and Infopower:An Interview with Dominic Boyer and Colin Koopman
No full textKirsten Hasberg talks to Dominic Boyer, anthropologist and author of Energopolitics: Wind and Power in the Anthroprocene, and to Colin Koopman, philosopher and author of How We Became our Data: A Genealogy of the Informational Person. Their books published in mid-2019 put forward novel conceptualizations of Foucauldian biopower, which they term infopower and energopower, respectively. Criss-crossing between philosophical conceptualizations and concrete problems like the struggles of renewable energy communities (Boyer) and the influence of economic thinking on datafication (Koopman), the conversations show how Foucauldian concepts are relevant to today's power struggles inherent to the energy transition and the digital transformation.Kirsten Hasberg talks to Dominic Boyer, anthropologist and author of Energopolitics: Wind and Power in the Anthroprocene, and to Colin Koopman, philosopher and author of How We Became our Data: A Genealogy of the Informational Person. Their books published in mid-2019 put forward novel conceptualizations of Foucauldian biopower, which they term infopower and energopower, respectively. Criss-crossing between philosophical conceptualizations and concrete problems like the struggles of renewable energy communities (Boyer) and the influence of economic thinking on datafication (Koopman), the conversations show how Foucauldian concepts are relevant to today's power struggles inherent to the energy transition and the digital transformation
Simple guide to urban land regularization in the informal settlements in Kenya
No full textAuthor: Dominic Mutuk
Mary\u27s Knowledge of Her Son\u27s Divinity at the Annunciation: The Papal Tradition
No full textAbout the author: Rev. Dominic Unger, O.F.M. Cap., has written widely on Marian scholarship and various scriptural questions
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