INTERNATIONAL STANDARD PROBLEM 50: THE UNIVERSITY OF PISA CONTRIBUTION

Cherubini, Marco,Lazzerini, Davide,Giannotti, Walter,D'auria, Francesco Korean Nuclear Society 2012 Nuclear Engineering and Technology Vol.44 No.6

The present paper deals with the participation of the University of Pisa in the last International Standard Problem (ISP) focused on system thermal hydraulic, which was led by the Korean Atomic Energy Research Institution (KAERI). The selected test was a Direct Vessel Injection (DVI) line break carried out at the ATLAS facility. University of Pisa participated, together with other eighteen institutions, in both blind and open phase of the analytical exercise pursuing its methodology for developing and qualifying a nodalization. Qualitative and quantitative analysis of the code results have been performed for both ISP-50 phases, the latter adopting the Fast Fourier Transfer Based Method (FFTBM). The experiment has been characterized by three-dimensional behavior in downcomer and core region. Even though an attempt to reproduce these phenomena, by developing a fictitious three-dimensional nodalization has been realized, the obtained results were generally acceptable but not fully satisfactory in replicating 3D behavior.

Control Methods in Data-Storage Systems

Cherubini, G.,Chung Choo Chung,Messner, W. C.,Moheimani, S. O. R. IEEE 2012 IEEE transactions on control systems technology Vol.20 No.2

<P>The recording performance of data-storage devices, in which write/read elements move relative to a storage medium to reliably store and retrieve information, depends on the capability of servo mechanisms to provide the necessary positioning accuracy. The desired characteristics of servo mechanisms for data-storage systems include robustness against variations of environmental parameters, high resolution, accuracy, stability, and fast response. This paper presents a comprehensive overview of advanced servo-control methods for data storage. The applications are to well-established recording technologies, including magnetic tape and magnetic disk systems as well as CD/DVD/Blue-Ray optical data-storage systems. Moreover, newer holographic and near-field optical systems and the emerging probe-storage technology are also addressed. Emphasis is given to the potential exhibited by the technologies considered for achieving ultra-high storage capacity, as required by the exploding demand in data-storage capacity for archival systems and massive multimedia data storage.</P>

Using FEMLAB for Gravitational Problems: Numerical Simulations for All

Christian Cherubini,Simonetta Filippi 한국물리학회 2006 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.49 No.2I

We discuss the possibility to solve modern numerical relativity problems by using .nite element methods (FEM). Adopting a \user friendly" software package for handling totally general systems of nonlinear partial dierential equations, FEMLAB, we model and numerically solve in a short time a Gowdy vacuum spacetime representing an inhomogeneous cosmology. Results agree perfectly with existing simulations in the recent literature based not on FEMs but on .nite dierence methods. Possible applications for non-relativistic astrophysics, general relativity, elementary particle physics, and more general theories of gravitation like EMDA and branes are discussed.

INTERNATIONAL STANDARD PROBLEM 50: THE UNIVERSITY OF PISA CONTRIBUTION

MARCO CHERUBINI,DAVIDE LAZZERINI,WALTER GIANNOTTI,FRANCESCO D’AURIA 한국원자력학회 2012 Nuclear Engineering and Technology Vol.44 No.6

The present paper deals with the participation of the University of Pisa in the last International Standard Problem (ISP)focused on system thermal hydraulic, which was led by the Korean Atomic Energy Research Institution (KAERI). The selected test was a Direct Vessel Injection (DVI) line break carried out at the ATLAS facility. University of Pisa participated, together with other eighteen institutions, in both blind and open phase of the analytical exercise pursuing its methodology for developing and qualifying a nodalization. Qualitative and quantitative analysis of the code results have been performed for both ISP-50phases, the latter adopting the Fast Fourier Transfer Based Method (FFTBM). The experiment has been characterized by threedimensional behavior in downcomer and core region. Even though an attempt to reproduce these phenomena, by developing a fictitious three-dimensional nodalization has been realized, the obtained results were generally acceptable but not fully satisfactory in replicating 3D behavior.

Boundary Conditions for Scattering Problems from Acoustic Black Holes

C. Cherubini,S. Filippi 한국물리학회 2010 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.56 No.5

Analog curved spacetimes emerging from non-relativistic condensed matter systems can be very useful in understanding general relativistic effects. In this article, we analyze different boundary conditions for scattering processes from an acoustic black hole, focusing in particular on the acoustic "black hole bomb" phenomenon in the time domain. More in detail, we develop a superradiant instability, which allows the extraction of energy from the central engine of the system by placing a "mirror"at some distance from the central object.

The exfoliation of irradiated nuclear graphite by treatment with organic solvent: a proposal for its recycling

Mauro Capone,Nadia Cherubini,Maria Letizia Cozzella,Alessandro Dodaro,Tiziana Guarcini 한국원자력학회 2019 Nuclear Engineering and Technology Vol.51 No.4

For the past 50 years, graphite has been widely used as a moderator, reflector and fuel matrix in differentkinds of gas-cooled reactors. Resulting in approximately 250,000 metric tons of irradiated graphitewaste. One of the most significant long-lived radioisotope from graphite reactors is carbon-14 (14C) [1]with a half-life of 5730 years, this makes it a huge concern for deep geologic disposal of nucleargraphite (NG). Considering the lifecycle of NG a number of waste management options have beendeveloped, mainly focused on the achievement the radiological requirements for disposal [2]. Theexisting approaches for recycling depend on the cost to be economically viable. In this new study, an affordable process to remove 14C has been proposed using samples taken fromthe Nuclear Power Plant in Latina (Italy) which have been used to investigate the capability of organicand inorganic solvents in removing 14C from exfoliated nuclear graphite, with the aim to design apracticable approach to obtain graphite for recycling or/and safety disposed as L& LLW.

Proposal of a prototype plant based on the exfoliation process for the treatment of irradiated graphite

Pozzetto, Silvia,Capone, Mauro,Cherubini, Nadia,Cozzella, Maria Letizia,Dodaro, Alessandro,Guidi, Giambattista Korean Nuclear Society 2020 Nuclear Engineering and Technology Vol.52 No.4

Most of irradiated graphite that should be disposed comes from moderators and reflectors of nuclear power plants. The quantity of irradiated graphite could be higher in the future if high-temperature reactors (HTRs) will be deployed. In this case noteworthy quantities of fuel pebbles containing semi-graphitic carbonaceous material should be added to the already existing 250,000 tons of irradiated graphite. Industry graphite is largely used in industrial applications for its high thermal and electrical conductivity and thermal and chemical resistance, making it a valuable material. Irradiated graphite constitutes a waste management challenge owing to the presence of long-lived radionuclides, such as ¹⁴C and ³⁶Cl. In the ENEA Nuclear Material Characterization Laboratory it has been successfully designed a procedure based on the exfoliation process organic solvent assisted, with the purpose of investigate the possibility of achieving graphite significantly less toxic that could be recycled for other purpose [1]. The objective of this paper is to evaluate the possibility of the scalability from laboratory to industrial dimensions of the exfoliation process and provide the prototype of a chemical plant for the treatment of irradiated graphite.

Uncertainty and sensitivity analysis in reactivity-initiated accident fuel modeling: synthesis of organisation for economic co-operation and development (OECD)/nuclear energy agency (NEA) benchmark on reactivity-initiated accident codes phase-II

Olivier Marchand,Jinzhao Zhang,Marco Cherubini 한국원자력학회 2018 Nuclear Engineering and Technology Vol.50 No.2

In the framework of OECD/NEA Working Group on Fuel Safety, a RIA fuel-rod-code Benchmark Phase Iwas organized in 2010e2013. It consisted of four experiments on highly irradiated fuel rodlets testedunder different experimental conditions. This benchmark revealed the need to better understand thebasic models incorporated in each code for realistic simulation of the complicated integral RIA tests withhigh burnup fuel rods. A second phase of the benchmark (Phase II) was thus launched early in 2014,which has been organized in two complementary activities: (1) comparison of the results of differentsimulations on simplified cases in order to provide additional bases for understanding the differences inmodelling of the concerned phenomena; (2) assessment of the uncertainty of the results. The presentpaper provides a summary and conclusions of the second activity of the Benchmark Phase II, which isbased on the input uncertainty propagation methodology. The main conclusion is that uncertaintiescannot fully explain the difference between the code predictions. Finally, based on the RIA benchmarkPhase-I and Phase-II conclusions, some recommendations are made.

Development and Performance Test of the Analysis Software for the CRIB Active Target

이필수,이춘식,문준영,채경육,차수미,Hidetoshi Yamaguchi,Taro Nakao,David M. Kahl,Shigeru Kubono,Silvio Cherubini,Seiya Hayakawa,Cosimo Signorini 한국물리학회 2015 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.66 No.3

Software for genuinely event-by-event analysis and event reconstruction of data obtained by usingan active target has been developed in the graphical user interface under the CERN ROOT framework. The primary motivation for developing the software was to provide physicists who performexperiments using an active target a more user-friendly environment for the purpose of investigatingthe performance of detection systems and obtaining ideas about physics from a large amount ofexperimental data. To test the performance of the software, we analyzed experimental data froma 16N radioactive ion beam experiment for α-decay measurements. As a result of the analysis, weobserved the Bragg curve and measured the range of the 16N RI beam in the detector. Data werecalibrated against the calculation after comparing the Bragg curve to the one obtained from anenergy loss calculation in P-10 gas. We present a detailed description of the analysis software andits test results.