1,720,962 research outputs found
A Preliminary Approach to the Neutronics of the Molten Salt Reactor by means of COMSOL Multiphysics
No full textThe Molten Salt Reactor (MSR), proposed along with other five innovative concepts of fission nuclear reactor by the Generation IV International Forum (GIF-IV), represents a challenging task from the modelling perspective because of the strong coupling
between neutronics and thermo-hydrodynamics due to liquid fuel circulation in the primary loop. In this paper COMSOL Multiphysics® is adopted to investigate the MSR neutronics, focusing on the steady-state core average conditions of the
Molten Salt Breeder Reactor (MSBR) developed at Oak Ridge National Laboratory (ORNL). The results achieved by COMSOL, adopting a two energy group diffusion model and using group
constants calculated by means of the deterministic code SCALE5.1, are compared with those achieved by the stochastic code MCNP for validation purpose. In particular, neutron flux profiles and integral quantities, like the effective multiplication
factor and homogenized cross sections, are evaluated and discussed. The model implemented in COMSOL is then used to study the effect of the fuel velocity on the neutronic behaviour of
the analysed MSBR core channel
Benchmark evaluation of reactor critical parameters and neutron fluxes distributions at zero power for the TRIGA Mark II reactor of the University of Pavia using the Monte Carlo code MCNP
No full textThe aim of this work was to develop a methodological approach based on Monte Carlo code for the neutronic analysis of the first core configuration of the TRIGA Mark II research reactor of the University of Pavia and the validation of the results by benchmarking with the experimental and operational data reported in the reactor Fist Criticality Final Report.
The neutron analysis was realised by means of the 3-D continuous-energy Monte Carlo code MCNP4C. The reactor model implemented represents in good detail all core components and allows the description of different core and fuel configurations with good versatility. Continuous-energy cross section data from ENDF/B-VI and ENDF/B-V and S(α, β) scattering functions from the ENDF/B-VI library were used. The results of the MCNP simulations and the experimental values show a very good agreement proving the goodness of the model
Preliminary Feasibility Study of a Water Space Reactor with an Innovative Reactivity Control System
Full text linkPower limitation represents a major issue within space applications aimed to human settlements on
solar system planets. Among these planets, Mars is considered the most attractive because of its
nearness to the Earth and the probable presence of minerals which can be used by the settlers to
live off the land. In this frame, small size nuclear power plants can be an interesting solution to
overcome the energy supply problem. This paper presents a preliminary feasibility study of a 100
kWe self-pressurized water space reactor, with the aim to design a system characterized by
compactness, intrinsic safety and simplicity of the main reactor control components. To this end an
innovative reactivity control system, based on the control of the primary coolant mass flow rate,
was adopted. The introduction of this system in the reactor design required a comprehensive core
neutronics analysis in order to properly quantify the effect of the coolant on the reactor behaviour
also as a function of the fuel burn-up. Here only the main results of this analysis, concerning
neutron flux profiles and multiplication factors, are discussed. Moreover preliminary results on
long term reactivity control are presented, showing the possibility to operate the reactor for as long
as 7 years with no need of human intervention
Transfer Function Modelling of the Lead-cooled Fast Reactor (LFR) Dynamics
No full textLead-cooled Fast Reactors (LFRs) are being deeply studied within the Generation IV International Forum (GIF) framework because of their features which well suit nuclear sustainability and safety. Different design configurations have been considered, each of them requiring different modelling approaches for the study of the reactor dynamics and in particular of the most critical transients in terms of safety and control.
In this work a linearized one-dimensional model of a lead-cooled fast reactor is presented assuming as reference design for the primary loop the European Lead SYstem (ELSY) reactor. Differently from the ELSY reference option, a supercritical water steam cycle is considered as secondary loop, which represents an attractive option for future developments of ELSY design. In order to properly describe the heat transfer in supercritical water, different correlations (available in open literature) have been analyzed and compared. The present model implements mass and energy equations, referred to a single-channel thermal-hydraulic analysis both for primary and secondary reactor system, handled in the frequency domain according to the theory of linear systems. The adopted transfer function approach simplifies the study of the reactor stability, and permitted to solve analytically in time the governing equations by
means of Laplace transform method. Limitation of computer cost is a further benefit.
The reactor dynamics has been characterized by simulating significant operational transients due to disturbances of input variables. In particular, system responses to perturbations of reactor power, feedwater temperature and mass flow rate, are discussed. Drawbacks due to the linearization and to the
appearance of non-minimum phase effects related to the secondary loop modelling are pointed out also in the view of future development of a reactor control strategy. A discussion on the non-minimum phase source is also presented
A Dynamic Model of a Lead-Cooled Fast Reactor (LFR) with a Supercritical Water Steam Cycle
No full textStudy of a new Automatic Reactor Power Control for the TRIGA Mark II Reactor at University of Pavia
No full textAbstract—The installation of a new Instrumentation and Control
(I&C) system for the TRIGA MARK II reactor at University of
Pavia has recently been completed in order to assure a safe and
continuous reactor operation for the future. The intervention
involved nearly the whole I&C system and required a channelby-
channel component substitution. One of the most sensitive
part of the intervention concerned the Automatic Reactor Power
Controller (ARPC) which permits to keep the reactor at an
operator-selected power level acting on the control rod devoted to
the fine regulation of system reactivity. This controller installed
can be set up using different control logics: currently the system
is working in relay mode. The main goal of the work presented in
this paper is to set up a Proportional-Integral-Derivative (PID)
configuration of the new controller installed on the TRIGA
reactor of Pavia so as to optimize the response to system
perturbations
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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