1,620 research outputs found
Supramolecular Chemistry and photophysical Properties of a New Gold (I) Cyclic Trinuclear Complex, [Au(μ-C2,N3-1-vinylimidazole)]3
No full textSupramolecular Chemistry and photophysical Properties of a New Gold (I) Cyclic Trinuclear Complex, [Au(μ-C2,N3-1-vinylimidazole)]3
R. Galassia, A. Burinia, C. S. Oumaroua, V. N. Nesterov b, M. A. Omary b.
a Dipartimento di Scienze Chimica, Università di Camerino, Via Sant Agostino, 1, 62032 Camerino, Italia
b Department of Chemistry, University of North Texas, Denton, TX 76203, USA
email: [email protected]
In the past years several cyclic trinuclear complexes (CTC’s) have been synthetized and characterized on the basis of the capacity of d10 transition metal ions to give bicoordinated linear compounds. This intriguing class of compounds display pi-acid/ pi-base properties that can be finely tuned by: the nature of the metal, the substituents on the ligand or the ligand itself. [1] These complexes are attractive building blocks to obtain supramolecular compounds showing interesting photopysical properties [2] or heterobimetallic cyclic trinuclear complexes with potential use in mixed-metal catalysis [3]. Here we report the synthesis of a novel gold (I) CTC, [Au(μ-C2,N3-1-vinylimidazole)]3, and the study of some photophysical properties of its supramolecular derivatives obtained by the intercalation of metal ions in between the metallocycles.
[1] S.M. Terkali, T.R. Cundari, M.A. Omary, J. Am. Chem. Soc. 2008, 130, 1669
[2] a) A. Burini, R. Bravi, J. P. Fackler Jr, Galassi R., T. A. Grant, M. A. Omary, B. R. Pietroni, R. J. Staples . Inorg. Chem. 2000, 39; 3158.b) Burini A, Fackler J. P, JR, Galassi R., Grant T. A, Omary M. A, Rawashdeh-Omary M. A, Pietroni B. R, Staples R.J. J. Am. Chem. Soc. 2000, 122; 11264.
[3] A. Mohamed, R. Galassi, F. Papa, A. Burini, J.P. Fackler , Jr. Inorg. Chem. 2006, 45, 7770-7776
[5] R. Galassi, S. Ricci, A. Burini, A. Macchioni, L. Rocchiagiani, F. Marmottini, S.M. Terkali, V.N. Nesterov, M.A. Omary, Inorg. Chem. 2013, 52, 14124-1413
Coinage metals trinuclear metallocycles: old and new aspects of this class of compounds
No full textCoinage metals trinuclear metallocycles: old and new aspects of this class of compounds
Galassi R. a, Oumarou C. S. a, Omary A. M. b, Nesterov V. b, Burini A.a
aSchool of Science and Technology, Chemistry Division, University of Camerino, Via S. Agostino 1, 62032 Camerino; e-mail: [email protected]
b Department of Chemistry, University of North Texas, Denton, 1155 Union Circle, TX 76203, USA; e-mail: [email protected]
Azoles such as imidazoles and pyrazoles are optimal bridging ligands to obtain C,N or N,N trinuclear coinage metals metallocycles. Since past decade till now, few worldwide research groups including us have focused their attention to their synthesis and characterization.[1] Moreover, the photophysical properties[2] the extended network of metallophilic bondings in the supramolecular structure and the pi-acid/pi-base chemistry[3] of these compounds directed the research to theoretical studies bringing to a better interpretation of the experimental behaviors.[4] Here we report the synthesis of new coinage metals metallocycles and their spectroscopic characterizations highlighting points of continuity with the previous analogs and new features for new perspective research lines. As in example, the 1-vinylimidazole resembles the acid-base chemistry of the 1-benzylimidazole gold(I) metallocycle, while substitution in position 4,5 of 1-benzylimidazole with electron-withdrawing group, do not allow the formation of metallocycles with the same synthethic route and mononuclear gold(I) derivatives have been obtained. The nature of the heterocycle and of the substituents, in addition to their position in the azolate ligand defines and tunes the properties of the final products.
References:
1) Galassi, R.; Burini, A.; Omary-Rawanashed, M., Omary, M. A., Comm. Inorg. Chem. 2014, in submission.
2) Rawashdeh-Omary, M. A.; Omary, M. A.; Fackler Jr, J. P, Galassi R., Pietroni, B. R.; Burini, A. J. Am. Chem. Soc 2001, 123; 9689-9691.
3) Burini, A.;. Fackler Jr, J. P; Galassi R., Grant, T. A.. Omary, M. A; Rawashdeh-Omary, M. A.; Pietroni, B. R.; Staples R. J. J. Am. Chem. Soc., 2000; 11264-11265.
4) Galassi, R.; Ricci, S.; Burini, A.; Macchioni, A; Marmottini, F.; Tekarli, S. M.; Nesterov, N.V.; Omary, M. A. Inorg. Chem. 2013, 52, 14124-14137
Atucha II Nuclear Reactor: Design Safety and Licensing
No full textAtucha II is the third reactor built and operated in Argentina, following Atucha I and Embalse. This is the First-Of-A-Kind (FOAK) in the world notwithstanding Atucha I. The following main facts relate to Atucha II:
This is a natural uranium nuclear reactor (like a CANDU, i.e. Canadian Deuterium Uranium), vessel equipped (like a PWR, i.e. Pressurized Water Reactor) and with established safety features (namely, basic philosophy and protection and control systems) of latest German PWR.
It has a positive coolant void reactivity coefficient (fission power tends to increase if coolant is removed from the core): excluding one (standard) CANDU reactor built in China and CANDU-type reactors in India, this is the only reactor entered in operation with a such a feature after the Chernobyl accident in 1986.
A relationship establishes among Break Opening Time (BOT), fast Boron Injection Time (BIT), Peak Clad Temperature (PCT) and Fission Power Peak (FPP) following a loss of coolant accident. This puts a challenge to the safety of the Atucha II reactor. The availability of computational tools, including uncertainty evaluation, allowed the characterization of the relationship BOT-BIT-PCT-FPP: not necessarily, the highest PCT coincides with the highest FPP.
The construction of the reactor, started at the end of 1980 has stopped and finally restarted in 2006: all main components were stored at the site, but no industry (noticeably, not even the initial designer who supplied the components) was available for planning or supervising the construction.
The owner and operator of the Plant, Nucleoléctrica Argentina SA (NA-SA), created a single-purpose multidisciplinary team, headed by José Luis Antúnez (JLA) to undertake the completion of the construction and the start-up of Atucha II. The team completed the commissioning in due time.
A system encompassing the complexity of CANDU and PWR had to be built (in 2006) in a Country having a long-lasting history within nuclear technology. Furthermore, a competent regulator was ready to act based on the latest findings by the international community in terms of nuclear safety technology. Then, the utility recognized the need for a deep understanding of the design principles of the reactor beyond and over the capability to install the various components.
In order to accomplish the construction of Atucha II, international groups of experts formed to support the utility and the regulators, respectively. Those groups, under the guidance of regulator and utility expert-staff, confronted each other in relation to the critical issues of the system.
An unprecedented and unrepeatable endeavour took place: the utility leaded group accessed and reviewed the documentation of Atucha II (i.e. a few million pages) and confirmed, independently of the original designers, the validity of the design choices and the safety margins. The blue prints, the measurements taken on the site and the material properties were the only basis of the analyses performed by the latest computational tools
Atucha II Nuclear Reactor: Design, Safety and Licensing @2021
F. D’Auria, O. Mazzantini, G. M. Galassi
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available from the scientific community. All of this allowed the reconstruction of the steps of the reactor design without adopting any assumption or coefficient proposed by original designers: a pioneering application was completed of the Best Estimate Plus Uncertainty (BEPU) approach. The regulators timely assessed and, following deep discussions, endorsed the approach and the results.
The BEPU application, first of a kind to the analysis of all transients, part of FSAR Chapter 15, is the result of a technology grow-up in the area of accident investigations that started in the middle of 1970, i.e. at OECD/NEA/CSNI. Planning and analysis of complex experiments, code, code-user and nodalization qualification, accuracy quantification, scaling, uncertainty evaluation, code coupling, probabilistic safety assessment and licensing connection of thermal hydraulics are among the concerned topics.
Therefore, we deemed the description of that endeavour worthy for the present book. The current authors directed a few dozen scientists (see acknowledgments where not all of them are listed) contributing to the efforts during less than ten years to accomplish the mission proposed by JLA. Four parts constitute the book.
Part 1, Chapters 1 and 2 – Atucha II reactor description.
Part 2, Chapters 3 to 8 – The BEPU approach.
Part 3, Chapters 9 to 13 – The Large Break Loss of Coolant (LBLOCA) issue.
Part 4, Chapters 14 to 24 – Insights from Accident Analysis.
The Part 1 deals with a short history of the Atucha II project and provides key reactor features. The heavy water moderator and coolant fluids enter in contact into the vessel through proper bypass flow paths and ensure cooling of the fuel rods and moderation of neutrons at high and reduced average temperatures, respectively.
The Part 2 discusses the BEPU approach, i.e. a prerequisite for understanding the reactor features. The BEPU approach, established in nuclear thermal hydraulics, includes the application of qualified numerical codes and uncertainty evaluation procedures. A pioneering effort brought to adopting the approach for the entire Accident Analysis (AA), part of ‘Chapter 15’ part of the standard Final Safety Analysis Report (FSAR). This required a previous acceptance of the approach by regulators.
The Part 3 deals with the LBLOCA. Following the initiating event or the double-ended guillotine break, the hot fluid in the core, which behaves as a neutron absorber in nominal conditions, vaporizes starting at a few milliseconds. The moderator remains liquid for a few seconds and induces a positive reactivity input. A power excursion follows in a situation of degraded cooling (FPP).
The BEPU application to the envelope of transients addressed in AA, Part 4, implied the coupling of a wide variety of numerical codes in the areas of neutron physics, nuclear fuel performance, structural mechanics, fission products source term in the core and radiological impact on the environment, in addition to thermal hydraulics.
Atucha II Nuclear Reactor: Design, Safety and Licensing @2021
F. D’Auria, O. Mazzantini, G. M. Galassi
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A dozen papers dealing with the above topics have been published, e.g. Adorni et al., 2011; Araneo et al., 2011; D’Auria et al., 2012; D’Auria et al., 2012a; Pecchia et al., 2015; Petruzzi et al., 2016; Moretti et al., 2018; Mazzantini et al. 2019; D’Auria, 2019; D’Auria et al., 2019.
The papers by Adorni et al., 2011; Araneo et al. 2011; D’Auria et al., 2012; and Pecchia et al., 2015, deal with nuclear fuel, Pressurized Thermal Shock (PTS), Instrumentation and Control (I & C) and neutron physics modelling, respectively: related matter is part of the BEPU approach of Atucha II.
The paper by Moretti et al., 2018, deals with a scale-1 experiment performed to confirm the quality of the fast boron injection system of Atucha II: this is essential to mitigate the fission power excursion that is consequent to the LBLOCA.
The paper by Mazzantini et al., 2019, discusses various issues connected with the Large Break LOCA analysis.
The papers by D’Auria et al., 2012a; Petruzzi et al., 2016, and D’Auria, 2019 provide a summary of the BEPU use in licensing, including achievements and perspectives in the area. Finally, BEPU constituted the key element for a proposal aimed at creating a connection between safety of existing rectors and advancements in nuclear science and technology, paper by D’Auria et al., 2019.
We issued several hundred documents within the framework of the cooperation between NA-SA and University of Pisa. Three summary documents are GRNSPG, 2008; GRNSPG 2008a, and GRNSPG, 2010. Industry property information is involved.
All those papers and documents guided the planning of the present book where we avoided infringing the property rights. Thus, the idea here is not to replicate the contents of those papers and documents, with one noticeable exception that is the paper by Mazzantini et al., 2019: this constitutes the basis for issuing the Part 3 of the book
Outline of User effect on Codes Predictions, 7th Meet. of CSNI THSB Task Group, Paris (F), June 26-28, 1990
No full textThe execution of a large number of pre-test and post-test analyses concerning (not only) International Standard Problems (ISP) each one with several participants with many of them using the same code version, showed an important impact on the code prediction which is not (or better, not entirely) associated with the nature of the code. This was called user effect. The user effect became a dominating topic in discussions and plant to improve the technology. The present report constitutes the origin of the ‘user-effect’ wording
Experience in the assessment of RELAP5/MOD2 code at Pisa University ICAP Meet., Grenoble (F), March 1-4, 1988
No full textA variety of experiments performed in Integral Test Facilities (ITF), like LOBI, LOFT, SEMISCALE, etc., were at the basis of the demonstration of capabilities and deficiencies of the Relp5 code. Both code deficiencies and capabilities were discussed at the International Code Assessment Program (ICAP) managed by United States Nuclear Regulatory Commission (US NRC). The opinion by UNIPI was presented in a Workshop held in Grenoble
OECD-CSNI ISP 27: outline of the comparison between blind prediction and experimental data, OECD-CSNI Final Meeting on ISP 27 - Grenoble (F), Jan. 14-15, 1992
No full textThe document deals with the description of results obtained by the Relap5 code in the post-test simulation of the Small Break Loss of Coolant Accident (SBLOCA) experiment performed in the Pressurized Water Reactor (PWR) experimental simulator BETHSY installed at the CEA-CENG Research Center in France. The Relap5 is the well-known computer code developed at Idaho National Laboratory in US: the code is in use at UNIPI since more than a decade. The BETHSY is a medium-large scale Integral Test Facility (ITF) simulating with full height, full pressure, full linear power a French type PWR. The concerned test was selected as International Standard Problem 27 (ISP 27) by OECD/NEA/CSNI (Organization for Economic Cooperation and Development / Nuclear Energy Agency / Committee on the Safety of Nuclear Installations). The document describes the results of the post-test calculation submitted (by UNIPI) to CEA (French Atomic Energy Commission) after the execution of the test; however the calculation results submitted before the execution of the test are discussed. This is part of post-test analysis: the comparison of about 60 calculated time trends with measured data allows an evaluation of the capabilities of the computer code and of the code user team in predicting the scenario of an accident. This is relevant for demonstrating the capabilities in evaluating safety margins of existing NPP, with main reference to PWR accident management situation (in this case)
Methodology for the evaluation of the reliability of passive systems
No full textWithin the co-operation between ENEA and University of Pisa (Contract No. 9840, serie 3A, signed in 1998),
a synergic study including applications of PSA (Probabilistic Safety Assessment) and thermohydraulics to the design of
new reactor concept, is foreseen. An application-oriented project was proposed by ENEA. This is identified hereafter as
PSA-TH Project. In this framework a working group has been set-up and supported by ENEA, involving scientific
personnel at ENEA, at Polytechnic of Milan (Department of Nuclear Engineering – CESNEF) and at University of Pisa
(Department of Mechanical, Nuclear and Production Engineering - DIMNP). Specialists in safety assessment and in
thermohydraulics are part of the working group.
Following the first meeting ‘exploratory activities’ have been conducted by each of the three branches (i.e.
ENEA, CESNEF and DIMNP) of the working group, with the aim of identifying a common way for the study and of
finalizing the PSA-TH Project proposed by the ENEA.
The ‘exploratory activity’ performed at DIMNP is documented in ref. [1] (see also App. 4 of the present
report).
At the end of the year 1999, a draft procedure was agreed within the group. The procedure and the results from
its application are discussed in the report.
The attention was focused toward passive systems. The general objective of the activity was to characterize the
transient thermalhydraulic performance of the passive system in probabilistic terms. A natural circulation loop including
an Isolation Condenser and the Reactor Pressure Vessel where power production occurs, has been selected for the
analysis. The following steps of the procedure can be distinguished:
(a) Characterization of design/operational status for the system,
(b) Characterization of parameters that are critical for the operation of the system,
(c) Assigning probability values to the status and to the parameters from steps (a) and (b),
(d) Modeling of the system by a qualified thermal-hydraulic system code,
(e) Performing a best estimate calculation and assigning failure criteria for the system performance,
(f) Deterministic selection of sets of boundary and initial conditions (6 sets),
(g) Statistic selection of sets of boundary and initial conditions – discrete probability distribution (69 sets),
(h) Statistic selection of sets of boundary and initial conditions – continuous probability distribution (69 sets),
(i) Association of each set to a code run (each set is also characterized by a probability value) and execution of 144
code runs (6+69+69),
(j) Based upon failure criteria defined under item (e) and upon results of code calculations, item (i), system
performance indicators could be derived (these consisted of ensembles of tables and plots). The deterministic
selection, item (f), combined with each of the statistic selections, items (g) or (h), causes the achievement of two
ensembles of system performance indicators.
‘Curves of merit’ for the system performance are significant results achieved from the application of the
procedure. These are assumed to be characteristic of the selected thermalhydraulic system and can be used to judge the
system acceptability and to compare the selected system with different systems
Solventless VOC chemisorption by silver metallocycles
No full textSolventless VOC chemisorption by silver metallocycles
Oumarou C. S.a, Tekarli S.,b Nesterov V.,b Omary M. A.,b Burini A.,a Galassi R.,a
aSchool of Science and Technology, Chemistry Division, University of Camerino, Via S. Agostino 1, 62032 Camerino; e-mail: [email protected]
b Department of Chemistry, University of North Texas, Denton, TX 76203, USA
Prior work has focused on detection/sensing aspects of VOCs,[1] this work proposes a method for their simultaneous filtration and removal through their strong chemisorption to a silver(I) metallocyclic trimer.[2] A solid cyclotrimer can quantitatively remove entire molar integers of VOCs (1-3 equivalents of VOCs per mole of the nitrated trimer) from the vapor phase in a solventless “green” chemical process, which is unprecedented for this class of cyclic d10 complexes.
Figure 1. Illustration of quadrupole-dipole interactions involving the [Ag(μ-Pz-2CF3)]3 or [Ag(3,5-(NO2)2pz)]3 trimers and acetonitrile using M06/CEP-31G(d). MEP surfaces are plotted in two manners, either mapped on electron density surfaces (rainbow plots with the color scale shown; isodensity = 0.0004) or positive (blue) and negative (red) regions in space (range = ± 2.2 a. u.; isodensity = 0.02)
[1] Yaghi et al., PNAS 2008, 105, 11623
[2] R. Galassi, S. Ricci, A. Burini, A. Macchioni, L. Rocchigiani, F. Marmottini, S. Tekarli, V. Nesterov, M. A. Omary, J. Am. Chem. Soc., 2013, submitted
Results of RELAP4/MOD6 code applications", Lectures L8, L9, L10, L13, L16 at Course on Thermal-hydraulic Phenomena in Nuclear Reactor Technology - Sofia (BG),
No full textA Course in Nuclear thermal-hydraulics was organized by UNIPI in Sofia at the time of the cold war (Soviet Union collapsed in 1991). Contacts crossing the iron curtain were extremely complex. The entire Course consists of several hundred slides (all preserved in paper format by the corresponding author) and a couple dozen lectures (see copies below). Two pages from the Course are reported below. The current lecture deals with the selected topics relevant in nuclear thermal-hydraulics –more details can be found in the copied program below
Applications of SYS TH codes to nuclear reactor design and accident analysis - Chapter 15
No full textEnvisaged Nuclear Power Plant transient performances are translated via experiments and expert judgement into lists of accidents. Accident scenarios are at the origin of phenomena. Phenomena are characterized by parameters or variables. The parameter values can be translated into requirements for predictive capabilities in thermal-hydraulics. The safety acceptance criteria consist of threshold parameter values. These are established by logical processes typically independent upon thermal-hydraulics knowledge. A global vision of nuclear reactor thermal-hydraulics is provided in the chapter
from the side of phenomena and accident scenarios: 12 reactor types are considered for the characterization of 47 accident scenarios cross-linked with 113 phenomena and 15 sets of “homogeneous” variable time trends
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