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Stefano Lorenzi
Department of Energy Politecnico di Milano Milano Italy

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Research article
Published: 30 March 2021 in International Journal for Numerical Methods in Engineering
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This paper presents two extensions of the Empirical Interpolation Method (EIM) designed to deal with vector interpolation problems. These Reduced Order Modeling (ROM) techniques are aimed at exploiting point‐wise (vector) measurements to obtain the unknown field reconstruction and they are preferred to other, more efficient, techniques as the Proper Orthogonal Decomposition (POD) because of their intrinsic capability to identify measurement positions and to perform field reconstruction. The "EIM‐orto" method implements rotation matrix coefficients and should be intended as a composition of rotations and dilatations of the vector basis functions. The "EIM‐orto" implements diagonal matrices coefficients and can be intended as the interpolation, component by component, of the unknown vector field, projected on a fixed reference system. The two techniques are tested over the lid‐driven cavity benchmark, in laminar conditions. The results obtained on this study case highlight how the EIM‐orto interpolation does not allow a reliable reconstructions, while the EIM‐roto interpolation allows reconstruction performances close to the POD ones (here used as reference method). In particular, the worst reconstruction error, i.e. the maximum L2 – norm of the residuals, decreases exponentially, reaching 5% with 25 basis functions. This result can be consider satisfactory, considering the nature of the problem.

ACS Style

Francesco A. B. Silva; Stefano Lorenzi; Antonio Cammi. An empirical interpolation method for two‐dimensional vector fields and vector measurements. International Journal for Numerical Methods in Engineering 2021, 1 .

AMA Style

Francesco A. B. Silva, Stefano Lorenzi, Antonio Cammi. An empirical interpolation method for two‐dimensional vector fields and vector measurements. International Journal for Numerical Methods in Engineering. 2021; ():1.

Chicago/Turabian Style

Francesco A. B. Silva; Stefano Lorenzi; Antonio Cammi. 2021. "An empirical interpolation method for two‐dimensional vector fields and vector measurements." International Journal for Numerical Methods in Engineering , no. : 1.

Journal article
Published: 25 February 2021 in Fusion Engineering and Design
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The Water Cooled Lithium Lead Test Blanket System (WCLL TBS) is one of the EU Test Blanket Systems candidate for being installed and operated in ITER. In view of its Conceptual Design Review by F4E and ITER Organization (IO), planned for mid-September 2020, several technical activities have been performed in the areas of WCLL TBS Ancillary Systems design. In this article the outcomes of the conceptual design phase of the four main Ancillary Systems of WCLL TBS, namely the Water Cooling System (WCS), the Coolant Purification System (CPS), the PbLi loop and the Tritium Extraction System (TES), are reported and critically discussed. In particular, for each Ancillary System hereafter are reported: i) a short design description, including the conceptual design of their main components together with their operative conditions under the so-called Normal Operational State (NOS), ii) the ESP-ESPN classification for their main components, and iii) their arrangement and integration in the assigned ITER areas (PC#16, Vertical Shaft, TCWS Vault, Galleries and Tritium Process Room).

ACS Style

Amelia Tincani; Pietro Arena; Maurizio Bruzzone; Ilenia Catanzaro; Cristiano Ciurluini; Alessandro Del Nevo; Pietro Alessandro Di Maio; Ruggero Forte; Fabio Giannetti; Stefano Lorenzi; Emanuela Martelli; Carlos Moreno; Rocco Mozzillo; Carlos Ortiz; Ferruccio Paoletti; Veronica Pierantoni; Italo Ricapito; Gandolfo Alessandro Spagnuolo; Andrea Tarallo; Claudio Tripodo; Antonio Cammi; Marco Utili; Konstantina Voukelatou; Erik Walcz; Balazs Lesko; Jessica Korzeniowska; Pierluigi Chiovaro; Vincenzo Narcisi. Conceptual design of the main Ancillary Systems of the ITER Water Cooled Lithium Lead Test Blanket System. Fusion Engineering and Design 2021, 167, 112345 .

AMA Style

Amelia Tincani, Pietro Arena, Maurizio Bruzzone, Ilenia Catanzaro, Cristiano Ciurluini, Alessandro Del Nevo, Pietro Alessandro Di Maio, Ruggero Forte, Fabio Giannetti, Stefano Lorenzi, Emanuela Martelli, Carlos Moreno, Rocco Mozzillo, Carlos Ortiz, Ferruccio Paoletti, Veronica Pierantoni, Italo Ricapito, Gandolfo Alessandro Spagnuolo, Andrea Tarallo, Claudio Tripodo, Antonio Cammi, Marco Utili, Konstantina Voukelatou, Erik Walcz, Balazs Lesko, Jessica Korzeniowska, Pierluigi Chiovaro, Vincenzo Narcisi. Conceptual design of the main Ancillary Systems of the ITER Water Cooled Lithium Lead Test Blanket System. Fusion Engineering and Design. 2021; 167 ():112345.

Chicago/Turabian Style

Amelia Tincani; Pietro Arena; Maurizio Bruzzone; Ilenia Catanzaro; Cristiano Ciurluini; Alessandro Del Nevo; Pietro Alessandro Di Maio; Ruggero Forte; Fabio Giannetti; Stefano Lorenzi; Emanuela Martelli; Carlos Moreno; Rocco Mozzillo; Carlos Ortiz; Ferruccio Paoletti; Veronica Pierantoni; Italo Ricapito; Gandolfo Alessandro Spagnuolo; Andrea Tarallo; Claudio Tripodo; Antonio Cammi; Marco Utili; Konstantina Voukelatou; Erik Walcz; Balazs Lesko; Jessica Korzeniowska; Pierluigi Chiovaro; Vincenzo Narcisi. 2021. "Conceptual design of the main Ancillary Systems of the ITER Water Cooled Lithium Lead Test Blanket System." Fusion Engineering and Design 167, no. : 112345.

Conference paper
Published: 22 February 2021 in EPJ Web of Conferences
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Modelling and simulation (M&S) have gradually become irreplaceable tools in the field of Nuclear Science and Technology (NS&T), including nuclear energy systems. This is partly due to growing computational resources and advances in computational science and partly to the difficulties to finance, build and license new experimental facilities. However, the utilization of M&S for research and development (R&D) and education and training (E&T) applications is somewhat hampered by limited accessibility to controlled and sensitive nuclear M&S tools as well as by the desires of the developers of these tools to retain their intellectual property (IP). Open-source software and open-access data are growingly perceived as means to accelerate innovation by promoting synergistic collaborative developments while lowering the barriers associated to code distribution, modification, and sharing. Open-source software development is ideal for R&D and E&T purposes because it permits the enhancement of understanding, the use of advanced computational methods and it promotes the cooperation among researchers and scientists, without rigorous constraints on quality assurance or reliance on proprietary data for technology-specific validation. As a fundamental research tool, this helps to mitigate constraints related to dual use of such technology. It is in this context that an initiative is being launched under the aegis of the International Atomic Energy Agency (IAEA) to promote the development and application of open-source multi-physics simulation in support of R&D and E&T in NS&T. This paper presents scope and objectives of this initiative.

ACS Style

C Fiorina; P Shriwise; A Dufresne; J Ragusa; K Ivanov; T Valentine; B Lindley; S Kelm; E Shwageraus; S Monti; C Batra; A Pautz; S Lorenzi; P Rubiolo; I Clifford; B Dechenaux. AN INITIATIVE FOR THE DEVELOPMENT AND APPLICATION OF OPEN-SOURCE MULTI-PHYSICS SIMULATION IN SUPPORT OF R&D AND E&T IN NUCLEAR SCIENCE AND TECHNOLOGY. EPJ Web of Conferences 2021, 247, 02040 .

AMA Style

C Fiorina, P Shriwise, A Dufresne, J Ragusa, K Ivanov, T Valentine, B Lindley, S Kelm, E Shwageraus, S Monti, C Batra, A Pautz, S Lorenzi, P Rubiolo, I Clifford, B Dechenaux. AN INITIATIVE FOR THE DEVELOPMENT AND APPLICATION OF OPEN-SOURCE MULTI-PHYSICS SIMULATION IN SUPPORT OF R&D AND E&T IN NUCLEAR SCIENCE AND TECHNOLOGY. EPJ Web of Conferences. 2021; 247 ():02040.

Chicago/Turabian Style

C Fiorina; P Shriwise; A Dufresne; J Ragusa; K Ivanov; T Valentine; B Lindley; S Kelm; E Shwageraus; S Monti; C Batra; A Pautz; S Lorenzi; P Rubiolo; I Clifford; B Dechenaux. 2021. "AN INITIATIVE FOR THE DEVELOPMENT AND APPLICATION OF OPEN-SOURCE MULTI-PHYSICS SIMULATION IN SUPPORT OF R&D AND E&T IN NUCLEAR SCIENCE AND TECHNOLOGY." EPJ Web of Conferences 247, no. : 02040.

Journal article
Published: 15 December 2020 in Sustainability
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The unique design features of the molten salt fast reactor (MSFR) should enable higher coolant temperatures than in conventional water reactors, with a significant improvement in the achievable thermodynamic performance. The use of a molten salt as both fuel and coolant, however, poses several advanced heat transfer challenges, such as the design of innovative heat exchangers and energy conversion systems. In this work, we address a preliminary but quantitative analysis of the energy conversion system for the MSFR, based on reference design data from the SAMOFAR H2020-EURATOM project. We consider three main technologies, i.e., the supercritical steam cycle, the closed helium cycle and the helium/steam combined cycle. Preliminary design results are presented for each technology, based on a simplified modelling approach. The considered cycles show promising efficiency improvements, with the best performance being proven by the supercritical steam cycle. The analysis also highlights the critical issue related to the risk of freezing of the molten salts within the secondary heat exchangers, due to the low inlet temperatures of the working fluids. Results show potential incompatibility between the freezing point of molten salts and the temperatures typical of steam cycles, while helium cycles offer the best chances of freezing avoidance. The combined cycle promises intermediate performance in terms of thermodynamic efficiency and thermal compatibility with molten salts comparable with closed helium cycles.

ACS Style

Andrea Di Ronco; Francesca Giacobbo; Guglielmo Lomonaco; Stefano Lorenzi; Xiang Wang; Antonio Cammi. Preliminary Analysis and Design of the Energy Conversion System for the Molten Salt Fast Reactor. Sustainability 2020, 12, 10497 .

AMA Style

Andrea Di Ronco, Francesca Giacobbo, Guglielmo Lomonaco, Stefano Lorenzi, Xiang Wang, Antonio Cammi. Preliminary Analysis and Design of the Energy Conversion System for the Molten Salt Fast Reactor. Sustainability. 2020; 12 (24):10497.

Chicago/Turabian Style

Andrea Di Ronco; Francesca Giacobbo; Guglielmo Lomonaco; Stefano Lorenzi; Xiang Wang; Antonio Cammi. 2020. "Preliminary Analysis and Design of the Energy Conversion System for the Molten Salt Fast Reactor." Sustainability 12, no. 24: 10497.

Journal article
Published: 11 March 2020 in Annals of Nuclear Energy
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Verification and validation of multi-physics codes dedicated to fast-spectrum molten salt reactors (MSR) is a very challenging task. Existing benchmarks are meant for single-physics codes, while experimental data for validation are absent. This is concerning, given the importance numerical simulations have in the development of fast MSR designs. Here, we propose the use of a coupled numerical benchmark specifically designed to assess the physics-coupling capabilities of the aforementioned codes. The benchmark focuses on the specific characteristics of fast MSRs and features a step-by-step approach, where physical phenomena are gradually coupled to easily identify sources of error. We collect and compare the results obtained during the benchmarking campaign of four multi-physics tools developed within the SAMOFAR project. Results show excellent agreement for all the steps of the benchmark. The benchmark generality and the broad spectrum of results provided constitute a useful tool for the testing and development of similar multi-physics codes.

ACS Style

Marco Tiberga; Rodrigo Gonzalez Gonzaga de Oliveira; Eric Cervi; Juan Antonio Blanco; Stefano Lorenzi; Manuele Aufiero; Danny Lathouwers; Pablo Rubiolo. Results from a multi-physics numerical benchmark for codes dedicated to molten salt fast reactors. Annals of Nuclear Energy 2020, 142, 107428 .

AMA Style

Marco Tiberga, Rodrigo Gonzalez Gonzaga de Oliveira, Eric Cervi, Juan Antonio Blanco, Stefano Lorenzi, Manuele Aufiero, Danny Lathouwers, Pablo Rubiolo. Results from a multi-physics numerical benchmark for codes dedicated to molten salt fast reactors. Annals of Nuclear Energy. 2020; 142 ():107428.

Chicago/Turabian Style

Marco Tiberga; Rodrigo Gonzalez Gonzaga de Oliveira; Eric Cervi; Juan Antonio Blanco; Stefano Lorenzi; Manuele Aufiero; Danny Lathouwers; Pablo Rubiolo. 2020. "Results from a multi-physics numerical benchmark for codes dedicated to molten salt fast reactors." Annals of Nuclear Energy 142, no. : 107428.

Journal article
Published: 17 February 2020 in Energies
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Fuel burnup analysis requires a high computational cost for full core calculations, due to the amount of the information processed for the total reaction rates in many burnup regions. Indeed, they reach the order of millions or more by a subdivision into radial and axial regions in a pin-by-pin description. In addition, if multi-physics approaches are adopted to consider the effects of temperature and density fields on fuel consumption, the computational load grows further. In this way, the need to find a compromise between computational cost and solution accuracy is a crucial issue in burnup analysis. To overcome this problem, the present work aims to develop a methodological approach to implement a Reduced Order Model (ROM), based on Proper Orthogonal Decomposition (POD), in fuel burnup analysis. We verify the approach on 4 years of burnup of the TMI-1 unit cell benchmark, by reconstructing fuel materials and burnup matrices over time with different levels of approximation. The results show that the modeling approach is able to reproduce reactivity and nuclide densities over time, where the accuracy increases with the number of basis functions employed.

ACS Style

Christian Castagna; Manuele Aufiero; Stefano Lorenzi; Guglielmo Lomonaco; Antonio Cammi. Development of a Reduced Order Model for Fuel Burnup Analysis. Energies 2020, 13, 890 .

AMA Style

Christian Castagna, Manuele Aufiero, Stefano Lorenzi, Guglielmo Lomonaco, Antonio Cammi. Development of a Reduced Order Model for Fuel Burnup Analysis. Energies. 2020; 13 (4):890.

Chicago/Turabian Style

Christian Castagna; Manuele Aufiero; Stefano Lorenzi; Guglielmo Lomonaco; Antonio Cammi. 2020. "Development of a Reduced Order Model for Fuel Burnup Analysis." Energies 13, no. 4: 890.

Journal article
Published: 03 February 2020 in Nuclear Engineering and Design
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The study of innovative nuclear reactors involves the use of increasingly complex numerical models. While such models provide a high-fidelity description of many non-linear coupled phenomena, they are not suited for many-query tasks such as design optimisation, uncertainty quantification, stability analysis or parameter identification due to the required computational effort. For this reason, a variety of techniques have been employed to reduce the complexity and surrogate the response of large nuclear systems. One example is the dynamic mode decomposition (DMD), a data-driven method which builds a low-dimensional eigenvalue-eigenvector representation of the underlying model from numerical data, and allows for non-intrusive analyses of the dynamical properties of the system without knowledge of the model itself. In this work, DMD is applied to the study of a free-dynamics fast transient of the Molten Salt Fast Reactor (MSFR), following a variation of the heat transfer coefficient. The numerical data is provided by a multiphysics model developed using the open-source CFD toolkit OpenFOAM. The aim of this work is to demonstrate the applicability of DMD to the study of large next-generation nuclear systems such as the MSFR. The results show the capabilities of DMD to extract and surrogate the dynamics of the MSFR following perturbation, including the initial non-linear dynamics and the final steady-state. Different values of parameters relevant to the construction of DMD models are tested, to provide some insights on the sensitivity of the method to the selection of the numerical data set and to the size of the reduced model.

ACS Style

Andrea Di Ronco; Carolina Introini; Eric Cervi; Stefano Lorenzi; Yeong Shin Jeong; Seok Bin Seo; In Cheol Bang; Francesca Giacobbo; Antonio Cammi. Dynamic mode decomposition for the stability analysis of the Molten Salt Fast Reactor core. Nuclear Engineering and Design 2020, 362, 110529 .

AMA Style

Andrea Di Ronco, Carolina Introini, Eric Cervi, Stefano Lorenzi, Yeong Shin Jeong, Seok Bin Seo, In Cheol Bang, Francesca Giacobbo, Antonio Cammi. Dynamic mode decomposition for the stability analysis of the Molten Salt Fast Reactor core. Nuclear Engineering and Design. 2020; 362 ():110529.

Chicago/Turabian Style

Andrea Di Ronco; Carolina Introini; Eric Cervi; Stefano Lorenzi; Yeong Shin Jeong; Seok Bin Seo; In Cheol Bang; Francesca Giacobbo; Antonio Cammi. 2020. "Dynamic mode decomposition for the stability analysis of the Molten Salt Fast Reactor core." Nuclear Engineering and Design 362, no. : 110529.

Journal article
Published: 01 November 2019 in Progress in Nuclear Energy
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ACS Style

A. Pini; A. Cammi; S. Lorenzi; M.T. Cauzzi; L. Luzzi. A CFD-based simulation tool for the stability analysis of natural circulation systems. Progress in Nuclear Energy 2019, 117, 1 .

AMA Style

A. Pini, A. Cammi, S. Lorenzi, M.T. Cauzzi, L. Luzzi. A CFD-based simulation tool for the stability analysis of natural circulation systems. Progress in Nuclear Energy. 2019; 117 ():1.

Chicago/Turabian Style

A. Pini; A. Cammi; S. Lorenzi; M.T. Cauzzi; L. Luzzi. 2019. "A CFD-based simulation tool for the stability analysis of natural circulation systems." Progress in Nuclear Energy 117, no. : 1.

Journal article
Published: 01 October 2019 in Annals of Nuclear Energy
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ACS Style

Eric Cervi; Stefano Lorenzi; Lelio Luzzi; Antonio Cammi. Multiphysics analysis of the MSFR helium bubbling system: A comparison between neutron diffusion, SP3 neutron transport and Monte Carlo approaches. Annals of Nuclear Energy 2019, 132, 227 -235.

AMA Style

Eric Cervi, Stefano Lorenzi, Lelio Luzzi, Antonio Cammi. Multiphysics analysis of the MSFR helium bubbling system: A comparison between neutron diffusion, SP3 neutron transport and Monte Carlo approaches. Annals of Nuclear Energy. 2019; 132 ():227-235.

Chicago/Turabian Style

Eric Cervi; Stefano Lorenzi; Lelio Luzzi; Antonio Cammi. 2019. "Multiphysics analysis of the MSFR helium bubbling system: A comparison between neutron diffusion, SP3 neutron transport and Monte Carlo approaches." Annals of Nuclear Energy 132, no. : 227-235.

Journal article
Published: 04 June 2019 in Progress in Nuclear Energy
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The trade-off between solution accuracy and computational burden is fundamental in numerical simulations, in particular for the fluid dynamics field. The aim of this work is to develop a Reduced Order Model (ROM) for heat transfer problems in Computational Fluid Dynamics (CFD). Such objective is achieved by including the energy equation in the POD-FV-ROM, a reduced order technique for Navier-Stokes equations described in Lorenzi et al. (2016). The technique, ad-hoc developed for the Finite Volume (FV) framework, relies on the Proper Orthogonal Decomposition (POD) and the projection of the physical fields onto subspaces of finite dimensions. Besides the extension to thermal-hydraulics, the work focuses on the capability to handle parametrized boundary conditions, especially the Neumann ones. To this aim a new approach is proposed and tested in two cases. In each case studied, the relative L2 norms of the differences for p, T, U resulted to be below 1% in steady state conditions.

ACS Style

Lorenzo Vergari; Antonio Cammi; Stefano Lorenzi. Reduced order modeling approach for parametrized thermal-hydraulics problems: inclusion of the energy equation in the POD-FV-ROM method. Progress in Nuclear Energy 2019, 118, 103071 .

AMA Style

Lorenzo Vergari, Antonio Cammi, Stefano Lorenzi. Reduced order modeling approach for parametrized thermal-hydraulics problems: inclusion of the energy equation in the POD-FV-ROM method. Progress in Nuclear Energy. 2019; 118 ():103071.

Chicago/Turabian Style

Lorenzo Vergari; Antonio Cammi; Stefano Lorenzi. 2019. "Reduced order modeling approach for parametrized thermal-hydraulics problems: inclusion of the energy equation in the POD-FV-ROM method." Progress in Nuclear Energy 118, no. : 103071.

Journal article
Published: 10 November 2018 in Progress in Nuclear Energy
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The primary aim of this work is to improve the analysis of the dynamic behaviour of the TRIGA Mark II reactor at the University of Pavia through a zero-dimensional approach. Besides the coupling between neutronics (point-reactor kinetics with six delayed neutron precursors group) and thermal-hydraulics (two-region model, with fuel and coolant) implemented in earlier works, the new model considers also the time behaviour of the mass flow rate due to natural circulation, of the neutron poisons and of the primary and secondary pool temperature. The system of coupled first-order differential equations is non-linear, as some state variables, such as the mass flow rate and the coolant temperature, multiply each other. The Simulink™ programming environment for dynamic analysis and control purposes is used to solve the system. A comparison with experimental data collected on-site for different reactor power transients and with measurements of the poison anti-reactivity during reactor shut-down and of the pool temperature allows the validation of the model. The model results and the experimental data reach a remarkable agreement. In addition, a linear stability analysis of the reactor is performed through the root locus and the stability map in terms of the thermal feedback coefficients. This analysis shows how the power level influences the dynamic of the system, and that, for certain values (always negative) of the fuel thermal feedback coefficient, positive values of the one for the moderator still ensures the system stability.

ACS Style

Carolina Introini; Antonio Cammi; Stefano Lorenzi; Giovanni Magrotti. An improved zero-dimensional model for simulation of TRIGA Mark II dynamic response. Progress in Nuclear Energy 2018, 111, 85 -96.

AMA Style

Carolina Introini, Antonio Cammi, Stefano Lorenzi, Giovanni Magrotti. An improved zero-dimensional model for simulation of TRIGA Mark II dynamic response. Progress in Nuclear Energy. 2018; 111 ():85-96.

Chicago/Turabian Style

Carolina Introini; Antonio Cammi; Stefano Lorenzi; Giovanni Magrotti. 2018. "An improved zero-dimensional model for simulation of TRIGA Mark II dynamic response." Progress in Nuclear Energy 111, no. : 85-96.

Journal article
Published: 08 November 2018 in Materials
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This paper studies Kalman filtering applied to Reynolds-Averaged Navier–Stokes (RANS) equations for turbulent flow. The integration of the Kalman estimator is extended to an implicit segregated method and to the thermodynamic analysis of turbulent flow, adding a sub-stepping procedure that ensures mass conservation at each time step and the compatibility among the unknowns involved. The accuracy of the algorithm is verified with respect to the heated lid-driven cavity benchmark, incorporating also temperature observations, comparing the augmented prediction of the Kalman filter with the Computational Fluid-Dynamic solution found on a fine grid.

ACS Style

Carolina Introini; Stefano Lorenzi; Antonio Cammi; Davide Baroli; Bernhard Peters; Stéphane Bordas. A Mass Conservative Kalman Filter Algorithm for Computational Thermo-Fluid Dynamics. Materials 2018, 11, 2222 .

AMA Style

Carolina Introini, Stefano Lorenzi, Antonio Cammi, Davide Baroli, Bernhard Peters, Stéphane Bordas. A Mass Conservative Kalman Filter Algorithm for Computational Thermo-Fluid Dynamics. Materials. 2018; 11 (11):2222.

Chicago/Turabian Style

Carolina Introini; Stefano Lorenzi; Antonio Cammi; Davide Baroli; Bernhard Peters; Stéphane Bordas. 2018. "A Mass Conservative Kalman Filter Algorithm for Computational Thermo-Fluid Dynamics." Materials 11, no. 11: 2222.

Proceedings article
Published: 22 July 2018 in Volume 6B: Thermal-Hydraulics and Safety Analyses
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Heat transfer phenomena involving internally heated fluid flows are of particular interest in several industrial applications, in chemical plants as in the nuclear field. This topic is relevant for the development of the Molten Salt Reactors (MSRs) since it involves the safety characteristics of the liquid molten salt fuel. In the literature, there is a lack of systematic studies on the heat transfer mechanism and correlations for flows in ducts featuring an internal heat source, apart from some analytical studies performed in Fiorina et al., “Thermal-hydraulics of internally heated molten salts and application to the MSFR”, Journal of physics, Conference series 501 (2014). In this work, the Nusselt number is computed multiplying the traditional Nu for internal flows times a corrective factor to account for the internal heat source. As a main outcome of this work, it is possible to obtain a CFD-based improved estimate of the corrective factor correlation for turbulent flow regime with respect to the work by Fiorina. The numerical CFD analysis is performed with the open source code Open FOAM. Despite its simplicity, the method is general and applicable for any geometrical and thermal situations.

ACS Style

Francesco Di Lecce; Sandra Dulla; Piero Ravetto; Antonio Cammi; Stefano Lorenzi; Carlo Fiorina. CFD-Based Correlation for Forced Convection Heat Transfer in Circular Ducts of Internally Heated Molten Salts. Volume 6B: Thermal-Hydraulics and Safety Analyses 2018, 1 .

AMA Style

Francesco Di Lecce, Sandra Dulla, Piero Ravetto, Antonio Cammi, Stefano Lorenzi, Carlo Fiorina. CFD-Based Correlation for Forced Convection Heat Transfer in Circular Ducts of Internally Heated Molten Salts. Volume 6B: Thermal-Hydraulics and Safety Analyses. 2018; ():1.

Chicago/Turabian Style

Francesco Di Lecce; Sandra Dulla; Piero Ravetto; Antonio Cammi; Stefano Lorenzi; Carlo Fiorina. 2018. "CFD-Based Correlation for Forced Convection Heat Transfer in Circular Ducts of Internally Heated Molten Salts." Volume 6B: Thermal-Hydraulics and Safety Analyses , no. : 1.

Preprint content
Published: 27 April 2018
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In the last decade, the importance of numerical simulations for the analysis of complex engineering systems, such as thermo-fluid dynamics in nuclear reactors, has grown exponentially. In spite of the large experimental databases available for validation of mathematical models, in order to identify the most suitable one for the system under investigation, the inverse integration of such data into the CFD model is nowadays an ongoing challenge. In addition, such integration could tackle the problem of propagation of epistemic uncertainties, both in the numerical model and in the experimental data. In this framework, the data-assimilation method allows for the dynamic incorporation of observations within the computational model. Perhaps the most famous among these methods, due to its simple implementation and yet robust nature, is the Kalman filter. Although this approach has found success in fields such as weather forecast and geoscience, its application in Computational Fluid-Dynamics (CFD) is still in its first stages. In this setting, a new algorithm based on the integration between the segregated approach, which is the most common method adopted by CFD applications for the solution of the incompressible Navier-Stokes equations, and a Kalman filter modified for fluid-dynamics problems, while preserving mass conservation of the solution, has already been developed and tested in a previous work. Whereas such method is able to robustly integrate experimental data within the numerical model, its computational cost increases with model complexity. In particular, in high-fidelity realistic scenarios the error covariance matrix for the model, which represents the uncertainties associated with it, becomes dense, thus affecting the efficiency and computational cost of the method. For this reason, due to the promised reduction of computational requirements recently investigated, which combines model reduction and data-assimilation, in this work a combination of reduced order model and mass-conservative Kalman filter within a segregated approach for CFD analysis is proposed. The novelty lies in the peculiar formulation of the Kalman filter and how to construct a low-dimensional manifold to approximate, with sufficient accuracy, the high fidelity model. With respect to literature, in which the full-order Kalman filter is applied to a reduced model, the reduction is performed directly on the integrated model in order to obtain a reduced-order Kalman filter already optimised for fluid-dynamics applications. In order to verify the capabilities of this approach, this reduced-order algorithm has been tested against the lid-driven cavity test case.

ACS Style

Carolina Introini; Stefano Lorenzi; Antonio Cammi; Davide Baroli. A Reduced Order Kalman Filter for Computational Fluid-Dynamics Applications. 2018, 1 .

AMA Style

Carolina Introini, Stefano Lorenzi, Antonio Cammi, Davide Baroli. A Reduced Order Kalman Filter for Computational Fluid-Dynamics Applications. . 2018; ():1.

Chicago/Turabian Style

Carolina Introini; Stefano Lorenzi; Antonio Cammi; Davide Baroli. 2018. "A Reduced Order Kalman Filter for Computational Fluid-Dynamics Applications." , no. : 1.

Journal article
Published: 01 April 2018 in Annals of Nuclear Energy
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This paper deals with the use of Reduced Order Methods for neutronics modelling. This approach is used whether both accuracy and computational efficiency are required. A very popular category of these methods is based on projection approaches which use spatial basis and test functions for the development of the reduced order model. The selection of the spatial basis and test functions used in the projection phase is a crucial issue since it has an impact on the accuracy and the computational cost. In this work, different methods for the creation of the spatial basis and the test functions are analysed. In particular, an Adjoint Proper Orthogonal Decomposition (APOD) method is proposed combining the properties of the Proper Orthogonal Decomposition and the use of the adjoint flux as test function in the neutronics framework. The different methods are applied to create a spatial neutronics model for the ALFRED reactor. The simulation results show that the APOD method gives better results compared to the other methods (Modal Method and standard Proper Orthogonal Decomposition) increasing the accuracy of the reduced order model or minimizing the computational cost.

ACS Style

Stefano Lorenzi. An Adjoint Proper Orthogonal Decomposition method for a neutronics reduced order model. Annals of Nuclear Energy 2018, 114, 245 -258.

AMA Style

Stefano Lorenzi. An Adjoint Proper Orthogonal Decomposition method for a neutronics reduced order model. Annals of Nuclear Energy. 2018; 114 ():245-258.

Chicago/Turabian Style

Stefano Lorenzi. 2018. "An Adjoint Proper Orthogonal Decomposition method for a neutronics reduced order model." Annals of Nuclear Energy 114, no. : 245-258.

Journal article
Published: 07 March 2018 in Reliability Engineering & System Safety
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With the extensive use of digital Instrumentation and Control (I&C) systems, Nuclear Power Plants (NPPs) are becoming Cyber-Physical Systems (CPSs). Their integrity can, then, be compromised also by security breaches (such as cyber attacks). Multiple failure modes (such as bias, drift and freezing) can occur, both due to random failures or induced by malicious external attacks. In this paper, we illustrate an exploration approach that, based on safety margins estimation, allows identifying the most vulnerable components to malicious external attacks. For demonstration, we apply the approach to the Advanced Lead-cooled Fast Reactor European Demonstrator (ALFRED). Its object-oriented model is embedded within a Monte Carlo (MC)-driven engine that injects different types of cyber attacks at random times and magnitudes. Safety margins are, then, calculated and used for identifying the most vulnerable CPS components. This allows selecting protections to make ALFRED resilient towards maliciously induced failures.

ACS Style

Wei Wang; Antonio Cammi; Francesco Di Maio; Stefano Lorenzi; Enrico Zio. A Monte Carlo-based exploration framework for identifying components vulnerable to cyber threats in nuclear power plants. Reliability Engineering & System Safety 2018, 175, 24 -37.

AMA Style

Wei Wang, Antonio Cammi, Francesco Di Maio, Stefano Lorenzi, Enrico Zio. A Monte Carlo-based exploration framework for identifying components vulnerable to cyber threats in nuclear power plants. Reliability Engineering & System Safety. 2018; 175 ():24-37.

Chicago/Turabian Style

Wei Wang; Antonio Cammi; Francesco Di Maio; Stefano Lorenzi; Enrico Zio. 2018. "A Monte Carlo-based exploration framework for identifying components vulnerable to cyber threats in nuclear power plants." Reliability Engineering & System Safety 175, no. : 24-37.

Journal article
Published: 01 March 2018 in Progress in Nuclear Energy
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The identification undesired or abnormal states of a nuclear power plant is of primary importance for defining accident prevention and mitigation actions. To this aim, computational models and simulators are frequently employed, as they allow to study the system response to different operational conditions. For complex systems like the nuclear power plants, this is in general challenging because the simulation tools are i) high-dimensional; ii) black-box; iii) dynamic and iv) computationally demanding. In this paper, an adaptive simulation framework recently proposed by some of the authors is tailored for the analysis of accident scenarios involving the control system of the Advanced Lead-cooled Fast Reactor European Demonstrator (ALFRED). The results confirm that the adaptive simulation framework proposed is effective in identifying critical regions of operation with a limited number of calls to the computationally expensive model. The time of occurrence and magnitude of the failures of the components of the control system are identified as key factors to characterize the critical regions. In particular, it is shown that the order of occurrence of the components’ failures strongly affects the evolution of the accident scenarios.

ACS Style

Pietro Turati; Antonio Cammi; Stefano Lorenzi; Nicola Pedroni; Enrico Zio. Adaptive simulation for failure identification in the Advanced Lead Fast Reactor European Demonstrator. Progress in Nuclear Energy 2018, 103, 176 -190.

AMA Style

Pietro Turati, Antonio Cammi, Stefano Lorenzi, Nicola Pedroni, Enrico Zio. Adaptive simulation for failure identification in the Advanced Lead Fast Reactor European Demonstrator. Progress in Nuclear Energy. 2018; 103 ():176-190.

Chicago/Turabian Style

Pietro Turati; Antonio Cammi; Stefano Lorenzi; Nicola Pedroni; Enrico Zio. 2018. "Adaptive simulation for failure identification in the Advanced Lead Fast Reactor European Demonstrator." Progress in Nuclear Energy 103, no. : 176-190.

Journal article
Published: 01 June 2017 in Applied Mathematical Modelling
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ACS Style

Stefano Lorenzi; Antonio Cammi; Lelio Luzzi; Gianluigi Rozza. A reduced order model for investigating the dynamics of the Gen-IV LFR coolant pool. Applied Mathematical Modelling 2017, 46, 263 -284.

AMA Style

Stefano Lorenzi, Antonio Cammi, Lelio Luzzi, Gianluigi Rozza. A reduced order model for investigating the dynamics of the Gen-IV LFR coolant pool. Applied Mathematical Modelling. 2017; 46 ():263-284.

Chicago/Turabian Style

Stefano Lorenzi; Antonio Cammi; Lelio Luzzi; Gianluigi Rozza. 2017. "A reduced order model for investigating the dynamics of the Gen-IV LFR coolant pool." Applied Mathematical Modelling 46, no. : 263-284.

Preprint
Published: 12 January 2017
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Vortex shedding around circular cylinders is a well known and studied phenomenon that appears in many engineering fields. In this work a Reduced Order Model (ROM) of the incompressible flow around a circular cylinder, built performing a Galerkin projection of the governing equations onto a lower dimensional space is presented. The reduced basis space is generated using a Proper Orthogonal Decomposition (POD) approach. In particular the focus is into (i) the correct reproduction of the pressure field, that in case of the vortex shedding phenomenon, is of primary importance for the calculation of the drag and lift coefficients; (ii) for this purpose the projection of the Governing equations (momentum equation and Poisson equation for pressure) is performed onto different reduced basis space for velocity and pressure, respectively; (iii) all the relevant modifications necessary to adapt standard finite element POD-Galerkin methods to a finite volume framework are presented. The accuracy of the reduced order model is assessed against full order results.

ACS Style

Giovanni Stabile; Saddam Hijazi; Andrea Mola; Stefano Lorenzi; Gianluigi Rozza. Advances in Reduced order modelling for CFD: vortex shedding around a circular cylinder using a POD-Galerkin method. 2017, 1 .

AMA Style

Giovanni Stabile, Saddam Hijazi, Andrea Mola, Stefano Lorenzi, Gianluigi Rozza. Advances in Reduced order modelling for CFD: vortex shedding around a circular cylinder using a POD-Galerkin method. . 2017; ():1.

Chicago/Turabian Style

Giovanni Stabile; Saddam Hijazi; Andrea Mola; Stefano Lorenzi; Gianluigi Rozza. 2017. "Advances in Reduced order modelling for CFD: vortex shedding around a circular cylinder using a POD-Galerkin method." , no. : 1.

Journal article
Published: 01 March 2016 in Progress in Nuclear Energy
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ACS Style

Roberto Ponciroli; Antonio Cammi; Stefano Lorenzi; Lelio Luzzi. Petri-net based modelling approach for ALFRED reactor operation and control system design. Progress in Nuclear Energy 2016, 87, 54 -66.

AMA Style

Roberto Ponciroli, Antonio Cammi, Stefano Lorenzi, Lelio Luzzi. Petri-net based modelling approach for ALFRED reactor operation and control system design. Progress in Nuclear Energy. 2016; 87 ():54-66.

Chicago/Turabian Style

Roberto Ponciroli; Antonio Cammi; Stefano Lorenzi; Lelio Luzzi. 2016. "Petri-net based modelling approach for ALFRED reactor operation and control system design." Progress in Nuclear Energy 87, no. : 54-66.