Partial Redesign of an Accelerator Driven System Target for Optimizing the Heat Removal and Minimizing the Pressure Drops

Accelerator Driven Systems (ADS) seem to be a good solution for safe nuclear waste transmutation. One of the most important challenges for this kind of machine is the target design, particularly for what concerning the target cooling system. In order to optimize this component a CFD-based approach has been chosen. After the definition of a reference design (Be target cooled by He), some parameters have been varied in order to optimize the thermal-fluid-dynamic features. The final optimized target design has an increased security margin for what regarding Be melting and reduces the maximum coolant velocity (and consequently even more the pressure drops)

Assessment of a 2D CFD model for a single phase natural circulation loop

The use of passive safety systems are more and more diffused in many technological fields. Natural circulation is probably one of the main phenomenon applied in this kind of systems: indeed, as known, by means of gravity and buoyancy forces, the fluids can circulate without any external power sources. In this paper a preliminary analysis (also by comparisons between experimental tests and numerical simulations) of a natural circulation based loop (namely a natural circulation based facility installed at University of Genova) is presented. Starting from some experimental results, the data deriving from CFD loop simulations (both in steady and in unsteady conditions) are used for a first preliminary validation, mainly in order to have a computational tool reliable and able to computationally simulate motion inversions related phenomena. The physical inversions phenomena are very well reproduced also by the a simplified numerical 2D model of the loop, and the physical considerations related to the temperature and velocity fluctuations during the transient simulations, are in agreement with the well-known observations formulated by Welander on the basis of a simple point source analysis scheme

A useful observable for estimating keff in fast subcritical systems

The neutron multiplication factor k-eff is a key quantity to characterize subcritical neutron multiplying devices and for understanting their physical behaviour, being related to the fundamental eigenvalue of Boltzmann transport equation. Both the maximum available power-and all quantities related to it, like, e.g. the effectiveness in burning nuclear wastes-as well as reactor kinetics and dynamics depend on k-eff. Nevertheless , k e f f is not directly measurable and its determination results from the solution of an inverse problem: minimizing model dependence of the solution for k-eff then becomes a critical issue, relevant both for practical and theoretical reasons

Development of CFD models and pre-test calculations for thermal-hydraulics and freezing experiments on Lead coolant

Heavy Liquid Metals (HLM) are objects of interest in the nuclear research sector because of their optimal thermal and neutronic properties; the development and the validation of models allowing to predict their behaviour are fundamental for the future development of the Generation IV energy systems. An experimental facility named SESAME-stand, is planned to be operated at Research Centre Rez (RC-Rez) under the framework of SESAME project. The aim of the facility is to study the solidification of Lead under GEN-IV Heavy Liquid Metal pool type nuclear reactors relevant conditions and to provide a database for the benchmarking and validation of numerical models. Corresponding CFD models are developed using commercial software and are used for the pre-test assessment and to support the experimental work. The aim of this paper is to describe the CFD models, explain how they are tested and used in order to define a valuable experimental matrix that will be needed in order to run the facility itself. First of all, the facility is introduced together with the range of foreseen investigations. The numerical models are then presented. Emphasis is given to the geometrical and physical assumptions. Different approaches of modelling are compared and discussed. Results from the pre-test simulations are illustrated. Encountered challenges and their relevance with regard to the experimental matrix and setup are commented

What "best practice" could be in Palliative Care: an analysis of statements on practice and ethics expressed by the main Health Organizations

<p>Abstract</p> <p>Background</p> <p>In palliative care it would be necessary to refer to a model. Nevertheless it seems that there are no official statements which state and describe that model. We carried out an analysis of the statements on practice and ethics of palliative care expressed by the main health organizations to show which dimensions of end-of-life care are taken into consideration.</p> <p>Methods</p> <p>The official documents by the most representative health organisations committed to the definition of policies and guidelines for palliative and end-of-life care had been considered. The documents were analysed through a framework of the components of end-of-life care derived from literature, which was composed of 4 main "areas" and of 12 "sub-areas".</p> <p>Results</p> <p>Overall, 34 organizations were identified, 7 international organisations, and 27 organisations operating on the national level in four different countries (Australia, Canada, UK and United States). Up to 56 documents were selected and analysed. Most of them (38) are position statements. Relevant quotations from the documents were presented by "areas" and "sub-areas". In general, the "sub-areas" of symptoms control as well as those referring to relational and social issues are more widely covered by the documents than the "sub-areas" related to "preparation" and to "existential condition". Indeed, the consistency of end-of-life choices with the patient's wishes, as well as completion and meaningfulness at the end of life is given only a minor relevance.</p> <p>Conclusions</p> <p>An integrated model of the best palliative care practice is generally lacking in the documents. It might be argued that the lack of a fixed and coherent model is due to the relevance of unavoidable context issues in palliative care, such as specific cultural settings, patient-centred variables, and family specificity. The implication is that palliative care staff have continuously to adapt their model of caring to the specific needs and values of each patient, more than applying a fixed, although maybe comprehensive, care model.</p

Theory, design and CFD analysis of a multi-blade screw pump evolving liquid lead for a GEN-IV LFR Nuclear Power Plant

In this presentation, a theoretical and computational analysis is presented of a multi-blade screw pump evolving liquid Lead as primary pump for the reference conceptual design of the Advanced Lead Fast Reactor European Demonstrator (ALFRED). The pump is analyzed at design operating conditions from the theoretical point of view to determine the optimal geometry according to the velocity triangles and then modeled with the 3D CFD code ANSYS CFX. The choice of a 3D simulation is dictated by the need to perform a detailed spatial simulation taking into account the peculiar geometry of the pump as well as the boundary layers and turbulence effects of the flow, which are typically tri-dimensional. The use of liquid Lead impacts significantly the fluid dynamic design of the pump because of the key requirement to avoid any velocity-related erosion phenomenon. Albeit some erosion-related issues remain to be fully addressed, the results of this 3D analysis show that a multi-blade screw pump could be a viable option for ALFRED from a thermo-fluid-dynamic point of view

Preliminary CFD assessment of an experimental test facility operating with heavy liquid metals

open5The CFD analysis of a Venturi nozzle operating in LBE (key component of the CIRCE facility, owned by ENEA) is presented in this paper. CIRCE is a facility developed to investigate in details the fluid-dynamic behavior of ADS and/or LFR reactor plants. The initial CFD simulations have been developed hand in hand with the comparison with experimental data: the test results was used to confirm the reliability of the CFD model, which, in turn, was used to improve the interpretation of the experimental data. The Venturi nozzle is modeled with a 3D CFD code (STAR-CCM+). Later on, the CFD model has been used to assess the performance of the component in conditions different from the ones tested in CIRCE: the performance of the Venturi are presented, in terms of pressure drops, for various operating conditions. Finally, the CFD analysis has been focused on the evaluation of the effects of the injection of an inert gas in the flow of the liquid coolant on the performance of the Venturi nozzle.openLizzoli, Matteo; Borreani, Walter; Devia, Francesco; Lomonaco, Guglielmo; Tarantino, MarianoLizzoli, Matteo; Borreani, Walter; Devia, Francesco; Lomonaco, Guglielmo; Tarantino, Marian

A short overview of ITER-like pulsed MCF reactors application as hybrid nuclear systems for actinides transmutation

The fusion-fission hybrid reactor is a promising technology that is likely to assume more and more importance in the global energy scenario in the coming years. Although this kind of nuclear system dates back to the earliest times of the fusion projects (when it was recognized that using fusion neutrons to \u201csupport\u201d nuclear fission fuel cycle could widely increase the exploitation of the fusion plants), it appears to receive relatively limited attention since the mid-1980s. Notwithstanding, hybrid fusion fission systems have been already studied for some decades, in the most prominent laboratories and a relatively large bibliography was produced. Obviously much more papers on this topic have been published in more recent years. The fusion-fission hybrid concept can use both the nuclear fusion and fission processes: in a typical application, neutrons from fusion reactions can be used to sustain the fission chain of a sub-critical system. This is the basis of the hybrid reactor concept: neutron generation is not produced just in neutron-induced fissions, but also as a \u201cby-product\u201d of the fusion reactions inside the nuclear fusion reactor \u201ccore\u201d (i.e., respectively, the void chamber for MCF or the fuel particles for ICF). This method allows to have an intrinsically safe facility (with a higher efficiency than a fusion reactor itself and a harder neutron energy spectrum than a fission reactor) which could be suitable for nuclear waste transmutation, too. In the last years, many initiatives on nuclear waste transmutation were proposed in order to reduce the long-term radiotoxicity of the wastes by eliminating a high fraction of the TRU from the SNF before their final disposal. In this frame, as already anticipated, hybrid fusion-fission systems could have an additional degree of freedom because of the independent source: this means that the neutron spectrum can be (reasonably) tailored for the transmutation purposes. In the present study a special focus has been devoted to the transmutation of SNF from fission reactors loaded in a fusion system, operated under the hypothesis to take into account the behaviour of a planned \u201creal\u201d (i.e. pulsed) MCF (ITER-like) plant

Numerical investigation on a jet pump evolving liquid lead for GEN-IV reactors

none4Heavy-liquid metals, such as lead and lead–bismuth eutectic, are promising candidates as coolant for advanced GEN-IV fast reactors as well as for Accelerator-Driven Systems. The advancing knowledge of the thermal-hydraulic behavior of these fluids leads to explore new geometries and new concepts aimed at optimizing the key components of a GEN-IV reactor for these fluids. In this paper, a theoretical and computational analysis is presented of a jet pump evolving liquid lead as primary pump for ALFRED (Advanced Lead Fast Reactor European Demonstrator). The jet pump is modeled with a 3D CFD code (FLUENT) and at design operating conditions. The analysis shows that a jet pump could be a viable solution for ALFRED (at least from a thermal-hydraulic point of view), albeit some technological issues remain to be fully addressed.mixedAndrea Mangialardo; Walter Borreani; Guglielmo Lomonaco; Fabrizio MaguglianiAndrea, Mangialardo; Borreani, Walter; Lomonaco, Guglielmo; Fabrizio, Maguglian

Design by theoretical and CFD analyses of a multi-blade screw pump evolving liquid lead for a Generation IV LFR

Lead-cooled fast reactor (LFR) has both a long history and a penchant of innovation. With early work related to its use for submarine propulsion dating to the 1950s, Russian scientists pioneered the development of reactors cooled by heavy liquid metals (HLM). More recently, there has been substantial interest in both critical and subcritical reactors cooled by lead (Pb) or Lead-Bismuth eutectic (LBE), not only in Russia, but also in Europe, Asia, and the USA. The growing knowledge of the thermal-fluid-dynamic properties of these fluids and the choice of the LFR as one of the six reactor types selected by Generation IV International Forum (GIF) for further research and development has fostered the exploration of new geometries and new concepts aimed at optimizing the key components that will be adopted in the Advanced Lead Fast Reactor European Demonstrator (ALFRED), the 300 MWth pool-type reactor aimed at proving the feasibility of the design concept adopted for the European Lead-cooled Fast Reactor (ELFR). In this paper, a theoretical and computational analysis is presented of a multi-blade screw pump evolving liquid Lead as primary pump for the adopted reference conceptual design of ALFRED. The pump is at first analyzed at design operating conditions from the theoretical point of view to determine the optimal geometry according to the velocity triangles and then modeled with a 3D CFD code (ANSYS CFX). The choice of a 3D simulation is dictated by the need to perform a detailed spatial simulation taking into account the peculiar geometry of the pump as well as the boundary layers and turbulence effects of the flow, which are typically tri-dimensional. The use of liquid Lead impacts significantly the fluid dynamic design of the pump because of the key requirement to avoid any erosion affects. These effects have a major impact on the performance, reliability and lifespan of the pump. Albeit some erosion-related issues remain to be fully addressed, the results of this analysis show that a multi-blade screw pump could be a viable option for ALFRED from a thermo-fluid-dynamic point of view