Exergy analysis of a PWR nuclear steam supply system – Part I, general theoretical model

The paper provides an alternative, novel methodology to perform the exergetic analysis of a Pressurized Nuclear Reactor (PWR) based on the strictest definition of fission temperature to get to a careful evaluation of Exergy Destruction and exergetic Efficiency of the component. Up today, the exegetic analyses of Nuclear Power Plants (NPP) have been based on the assumption that Fission Exergy and Fission Energy are almost the same having assumed Carnot Factor almost equal to 1 as Tfiss >>T0. This assumption is based on some simplified hypotheses concerning fission temperature as applied in the definition of the Fission Exergy itself, whose value, to the best knowledge of the authors, was never modeled. On the contrary, in the first part of the paper, the authors present the results of an ongoing research, just aimed at evaluating the Exergy efficiency of the heat exchange in a PWR reactor, whose first results were already presented in [1], based on the most detailed modeling of Tfiss. The modeling, referring to a steady-state operational mode of the Reactor, takes into account all heat transfer phenomena between nuclear fuel UO2, its Zircaloy clad, cooling water, vessel material and the external environment. In the second part of the paper, the Exergy analysis is extended to all main Reactor Cooling System components (Vertical recirculating type Steam Generator, primary coolant pump and piping) with the aim to compare the Exergy Destructions and exergetic Efficiencies of the RPV with those of the other components of the Nuclear Steam Supply System, NSSS. In the Part II of the same paper,, "Exergy Analysis of a PWR Nuclear Steam Supply System - II part: a case study ", a test case is exemplified with the aim to compare the results obtained applying the methodology in question with those obtained applying the most established methodology adopted by other authors

Exergy analysis of a PWR nuclear steam supply system - II part: a case study

The paper shows the results of the exergetic analysis of the Nuclear Steam Supply System (NSSS) of the MARS Pressurized Light Water Reactor using the theoretical methodology described in the authors’ previous works [1] and [2]. The analysis firstly aims at a novel assessment of the irreversibilities occurred in the nuclear reactor vessel to compare the results, in terms of Exergy Destruction and exergetic Efficiency, with those obtained adopting one of the most employed methodology as reference. The comparison showed that a detailed exergetic analysis, mainly aimed to strictly assess the fission temperature, can lead to a higher estimate of the PWR exergetic Efficiency values

Minority Segregation Processes in an Urban Context: a Comparison between Paris and Rome Recent trends in ethnic segregation in cities: Paris and Rome compared

Il processo di segregazione delle minoranze etniche assume caratteristiche diverse nei paesi di antica immigrazione (Francia, Gran Bretagna, Paesi Bassi, Germania) rispetto a quanto osservato in quelli di nuovo accoglimento (Italia, Spagna, Grecia e Portogallo). L'analisi condotta nel contributo mette a confronto due città globali (Parigi e Roma, aree urbane appartenenti a due diversi gruppi di paesi tra quelli citati) che ospitano una consistenza presenza straniera. Contrariamente alle attese non sembra emergere un aumento della segregazione etnica nelle due città, dove anzi sembrerebbe manifestarsi un contenimento delle differenze tra le modalità insediative della popolazione straniera e di quella autoctona.The process of minority segregation within global cities is a complex phenomenon. In the European urban context, the process of minority segregation seems to differ in the old immigration countries (France, UK, Netherlands, Germany) from the new immigration countries (Italy, Greece, Spain, Portugal). The analysis compares two global cities (Paris and Rome), taking into consideration the current evolution of the minority segregation pattern. The study shows that no traces of increasing segregation emerge in either of the cities

Exergy analysis of a PWR core heat transfer

The exergetic analysis, a methodology of thermodynamics that quantifies of energy losses associated with irreversibility, allows to optimize the efficiencies of the various stages of a transformation process and thus its overall efficiency. In this contribution, a novel approach to the exergetic analysis is applied to the energy transformations taking place within the core of a nuclear reactor. To perform such analysis, reference was made to a pressurized light-water reactor (PWR), modeling the heat exchanges between the fuel assemblies and the coolant fluid in the core through the balance of incoming and outgoing mass and energy flows, incoming and outgoing the reactor. The results of the analysis are validated through a comparison with the actual reactor operating parameters. The main goals of the work –part of a wider ongoing research effort- are to develop the thermo-economic analysis of a PWR nuclear power plant (NPP) to assess the actual cost of the products obtainable downstream of the NPP (electric energy and thermal energy for industrial and civil users, very different products in terms of exergy contents), and to compare with the costs of similar products obtained from conventional thermal power plants

Foreign Immigration and pull factors in Italy : a spatial approach

Significant changes have affected currently internal mobility in Italy. We try to understand what are the variables that allow a place to attract population. This work focuses on the foreign population and aims to detect the factors that push immigrant population towards Italian municipalities. We want to verify whether the action is different between movements of foreigners already resident in Italy and of immigrants coming directly from abroad. Data on flows, stock of populations and socioeconomic variables on Italian municipalities from Istat, Ministry of Economy and Sole 24 were exploited. Methods used are regression analyses enriched with spatial factors with reference to the possible action of spatial variables through the building of OLS, spatial lag and spatial error models

Hα Moreton waves observed on December 06, 2006: A 2D case study

Context. We present high temporal resolution observations of a Moreton wave event detected with the Hα Solar Telescope for Argentina (HASTA) in the Hα line 656.3 nm, on December 6, 2006. Aims. The aim is to contribute to the discussion about the nature and triggering mechanisms of Moreton wave events. Methods. We describe the HASTA telescope capabilities and the observational techniques. We carried out a detailed analysis to determine the flare onset, the radiant point location, the kinematics of the disturbance and the activation time of two distant filaments. We used a 2D reconstruction of the HASTA and corresponding TRACE observations, together with conventional techniques, to analyze the probable origin of the phenomenon. Results. The kinematic parameters and the probable onset time of the Moreton wave event are determined. A small-scale ejectum and the winking of two remote filaments are analyzed to discuss their relation with the Moreton disturbance. Conclusions. The analysis of the Moreton wave event favors the hypothesis that the phenomenon can be described as the chromospheric imprint of a single fast coronal shock triggered from a single source in association with a coronal mass ejection. Its onset time is concurrent with a Lorentz force peak measured in the photosphere, as stated by other authors. However, the existence of multiple shock waves that were generated almost simultaneously cannot be discarded.Fil: Francile, Carlos Natale. Universidad Nacional de San Juan. Facultad de Cs.exactas Fisicas y Naturales. Departamento de Informatica. Observat.astron. Felix Aguilar;Fil: Costa, Andrea. Consejo Nacional de Invest.cientif.y Tecnicas. Centro Cientifico Tecnol.conicet - Cordoba. Instituto de Astronomia Teorica y Experimental;Fil: Luoni, Maria Luisa. Consejo Nacional de Invest.cientif.y Tecnicas. Oficina de Coordinacion Administrativa Ciudad Universitaria. Instituto de Astronomia y Fisica del Espacio(i);Fil: Elaskar, Sergio Amado. Universidad Nacional de Cordoba. Facultad de Cs.exactas Fisicas y Naturales

Reuse of almond by-products: functionalization of traditional semolina sourdough bread with almond skin

Almond production generates large amounts of by-products rich in polyphenols. In this study, almond skin was explored as a valuable food ingredient in bread making. To this purpose, almond skin was used to produce functional products modifying a traditional sourdough bread recipe. The doughs were prepared replacing semolina with powdered almond skin (PAS) at 5 and 10 % (w/w). Sourdough inoculum was started with a mix of lactic acid bacteria (LAB) and propagated in semolina until reaching pH 3.7. The pH of PAS added breads was higher than that of control (CTR) breads before and after fermentation. Plate counts showed a similar evolution of LAB and total mesophilic microorganisms, but members of Enterobacteriaceae and coliform were detectable in PAS doughs. Illumina data clearly showed a dominance of lactobacilli in all trials, but PAS doughs displayed the presence of Bacillus. The final bread characteristics were influenced by PAS and its addition percentage; in particular, crust and crumb colour resulted darker, the alveolation decreased and, regarding sensory attributes, odour intensity increased, while bread odour diminished. In presence of PAS, bread emissions were characterized by lower percentages of alcohols and aromatic hydrocarbons and higher percentages of the other volatile compound classes, especially terpenoids like β-pinene, β-myrcene and limonene than CTR trial. After in vitro simulated digestion, the final release of phytochemicals from 10 % PAS bread was almost 100 %. Thus, PAS determined an increase of the antioxidant capacity of the breads. Phytochemicals released from digested PAS-fortified bread can provide antioxidant protection in a complex biological environment such as human intestinal-like cells. Besides the positive functional properties of PAS, this work also evidenced the hygienic issues of almond skin and, in order to avoid potential risks for the human health, highlighted the need to preserve its microbiological characteristics during storage for their reuse in bread productio