DOCSLIB.ORG

The Aqueous Solubility and Speciation Analysis for Uranium, Neptunium and Selenium by the Geochemical Code (Eq3/6)

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
The Aqueous Solubility and Speciation Analysis for Uranium, Neptunium and Selenium by the Geochemical Code (Eq3/6) JAERI-Research--95-069 JAERI-Research JP9512224 95-069 THE AQUEOUS SOLUBILITY AND SPECIATION ANALYSIS FOR URANIUM, NEPTUNIUM AND SELENIUM BY THE GEOCHEMICAL CODE (EQ3/6) November 1995 Seiji TAKEDA, Shigeki SHIMA, Hideo KIMURA and Hideo MATSUZURU Japan Atomic Energy Research Institute 2 7 Ife 0 7 *v ,t:- I- 12, tl \^M-1)W9ir)\iy^'&M~'hPJ L "C^SWF'ft&-;lnl WfAT-ftWft^Mittf ffiOT/ffiftftiS (=p3l9-ll (T319-11 "^JteicW-fflSWfflrjIuf/iWB AVftf-iiWKmH) t-Wylz i h'MV&.M*• Hz. This report is issued irregularly. Inquiries about availability of the reports should be addressed to Information Division. Department of Technical Information, Japan Atomic Energy Research Institute, To1' li- mura, Naka-gun, Ibaraki-ken 319-11, Japan. ©Japan Atomic Energy Research Institute, 1995 4:)fii /• )} Wf % JAERI-Research 95-069 The Aqueous Solubility and Speciation Analysis for Uranium, Neptunium and Selenium by the Geochemical Code(EQ3/6) Seiji TAKEDA, Shigeki SHIMA, Hideo KIMURA and Hideo MATSUZURU Department of Environmental Safety Research Tokai Research Establishment Japan Atomic Energy Research Institute Tokai-mura, Naka-gun, Ibaraki-ken (Received October 2, 1995) The geochemical condition of a geologic disposal system of HLW controls the solubility and physicochemical forms of dominant aqueous species for elements, which are one of essential information required for safety assessment. Based on the measured compositions of groundwater, the compositions of groundwater in the disposal system were calculated. The solubility and speciation analyses for the polyvalent elements, uranium, neptunium, and selenium, were performed by the geochemical code EQ3/6. The results obtained were compared with the data appeared in the literatures on the solubilities and speciations. The geochemical behaviors of the elements with respect to the solubility and speciation could quantitatively be elucidated for the compositions of the interstitial waters in an engineered barrier and ground water in a natural barrier. In the pH range of neutral to alkali, the solubilities of U and Np tend to increase with an increase of the carbonate concentration in groundwater. This carbonate concentration dependence of the solubility was also estimated. In the engineered barrier the predominant aqueous species were specified, and in the natural barrier the change of aqueous species was also predicted while the chemical compositions changed from the reducing to oxidizing conditions. The dominant aqueous species for the elements, which migrate in and through the disposal system, were determined by the speciation analysis. JAERI- Research 95-069 Keywords: Geochemical Model, Geochemistry, Solubility and Speciation Analysis, Chemical Composition, Eh-pH Condition, Thermodynamic Data, Groundwater, Uranium, Neptunium, Selenium, Radioactive Waste Disposal, High-level Radioactive Waste, Safety Assessment JAERI- Research 95-069 CHLW) , Np, S : T319-11 -4 JAERI-Research 95-069 Contents 1. Introduction 1 2. Geochemical Model 3 2.1 Geochemical Code 3 2.2 Methodology of Analysis 5 2.3 Chemical Composition of Groundwater 7 2.4 Thermodynamic Data 10 2.5 Solid Phase in Natural Groundwater 15 3. Results of Analysis 17 3.1 Uranium 17 3.2 Neptunium 24 3.3 Selenium 29 4. Conclusion 33 4.1 Solubility and Speciation in the Engineered Barrier 34 4.2 Solubility and Speciation in the Natural Barrier 34 Reference 37 Appendix Thermodynamics Data for Uranium, Neptunium, and Selenium 40 V JAERI-Research 95-069 a 1 [^ gA 1 1. rr Htm l 2. fife^-ft^^x;!/ 3 2. 1 ft&I£fl^3- K 3 2. 2 B?fff¥& 5 2. 3 «lT7J<©{(:^#f4 7 2. 4 miJ^T-? 10 2. 5 ifeTTKS^Cfclt^Sffi 15 3. JS¥«fig% 17 3. 1 Uranium 17 3. 2 Neptunium 24 3. 3 Selenium 29 4. %a m 33 4. 1 AX'OjTCtettSjgJB&fcftSMi 34 4.2 ^&'<y TiztstfzfeftBtkftsm 34 i 37 U, Np, Se©fi^^«]r-^ 40 Vi JAERI-Research 95-069 1. INTRODUCTION In the safety assessment for deep geologic disposal of high-level radioactive waste (HLW), the geochemical condition of the disposal system is one of important factors, which govern the performance of the multibarrier system consisting of engineered and natural barriers. The geochemical condition controls the corrosion of metallic containers (canister and overpack) by an interstitial water in the engineered barrier, determine the dissolution of radionuclides from in a waste form, and also govern a chemical form of radionuclides which migrate through the multibarrier. Figure 1 shows the relation between the chemical condition of groundwater and parameters involved in radionuclide transport models to be used in the long-term safety assessment. Such parameters as the solubility and the distribution coefficient of elements depend significantly on the groundwater chemical condition. The distribution coefficient of a specific element, which is an equilibrium parameter to define partitioning of a solute between a solid and a liquid phase, will vary with possible chemical forms of the element in an aqueous solution, e.g., cationic, anionic and nonionic forms. Solubility and thermodynamic data have been obtained from the experiments with solutions of relatively simple compositions compared with natural groundwater. It might be difficult to make the direct estimation, based on these experimental measurements, of their solubilities in solutions containing many kinds of co-ions. The effects of many kinds of aqueous species coexisting in solutions are not negligible to determine the solubility of a specific species. Therefore aqueous solubility and speciation in geochemical environments are subjected to calculations by using geochemical models, based on reliable thermodynamic data obtained from the experiments with solutions of relatively simple compositions. The time durations of these experiments are at the longest a few years. The time scale to consider in the safety assessment is of the orders of at least a few thousand years or more. The change in the long-term chemical compositions in groundwater must be predicted. Considering the circumstances mentioned above, based on the measured characteristics of the deep groundwater, the solubility and speciation analyses for some kinds of the groundwater have been undertaken by SKI (Swedish Nuclear Power Inspectorate, Sweden)(1) and SKB (Swedish Nuclear Fuel and Waste Management Co., Sweden)(2). Chemical interactions between solutions and minerals under physical and chemical conditions of a deep geologic environment can be modeled by the geochemical code, e.g., PHREEQE(3) and EQ3/6(4). The geochemical code must be supported by thermodynamic data, and the reliability of the analyzed results of solubility and speciation thereby depends on the credibility of the thermodynamic data. The thermodynamic data of some kinds of elements have been collected by OECD/NEA. Most of the thermodynamic data used here were obtained from OECD/NEA, and were selected by the criterion of thereliable data used in many literatures. Reacent literatures concerning thermodynamic data of elements - 1 - JAERI-Research 95-069 were also cited. In this report, the aqueous solubility and speciation of several polyvalent elements were analyzed by the geochemical code rystem EQ3/6 by assuming the thermodynamic equilibrium, under some chemical conditions of the groundwater, which are expected in near and far fields. Considering the space- and time-varying chemical characteristic of the groundwater, two types of models for the groundwater were assumed. For the first model (Model 1), the chemical compositions of the interstitial water in the engineered barrier under the reducing conditions were assumed, and for the second model (Model 2), the granitic groundwater in the natural barrier. These chemical compositions were calculateded by the geochemical code by assuming the thermodynamic equilibrium, based on the measured compositions of groundwater. The results obtained here were compared with the literatures on solubility and speciation. < Chemical condition > •pH • redox potential (Eh) • compositon of aqueous solution Experimental data: I Solubility, Speciation, Solubility and speciatbn Equilibrium constants, analysis by geochemical Thermodynamics, etc. code I I Radionuclide transport models used for long-term safety assessment Engineered barrier < Parameters > Transport/ • Solubility I migration • Distribution coefficient Natural barrier etc. Fig. 1 Relation between chemical conditions in groundwater and radonuclide transport models used for long-term safety assessment 2 - JAERI-Research 95-069 2. GEOCHEMICAL MODEL 2.1 Geochemical Code The geochemical software package EQ3/6 (version 3245) (4)(5)(6> consists of main two kinds of the geochemical codes, the EQ3NR code and the EQ6 code, and is supported by the thermodynamic data base and the conversion programs for this data base. It is possible for EQ3/6 to model geochemical processes such as chemical interactions between water-solid or water- mineral. The geochemical code EQ3/6 has been used in the solubility and speciation analyses for many aqueous environments, and known as the code with a high reliability. The flow of information between data files and codes for the EQ3/6 package is shown in Fig. 2. The MCRT code builds the equilibrium constants for aqueous species, minerals, and gases from the thermodynamic data base, and the output file is given as a text form. The EQPT is the preprocessor for the EQ3/6 data base, and the input of the EQPT code is the output of MCRT. Based on the thermodynamic data, concentrations and abundances of individual aqueous species are calculated by the Newton-Raphson method.
Load more

Recommended publications
  • Synthesis of Metal Selenide Semiconductor Nanocrystals Using Selenium Dioxide As Precursor
    SYNTHESIS OF METAL SELENIDE SEMICONDUCTOR NANOCRYSTALS USING SELENIUM DIOXIDE AS PRECURSOR By XIAN CHEN A THESIS PRESENTED TO THE GRADUATE SCHOOL OF THE UNIVERSITY OF FLORIDA IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE UNIVERSITY OF FLORIDA 2007 1 © 2007 Xian Chen 2 To my parents 3 ACKNOWLEDGMENTS Above all, I would like to thank my parents for what they have done for me through these years. I would not have been able to get to where I am today without their love and support. I would like to thank my advisor, Dr. Charles Cao, for his advice on my research and life and for the valuable help during my difficult times. I also would like to thank Dr. Yongan Yang for his kindness and helpful discussion. I learned experiment techniques, knowledge, how to do research and so on from him. I also appreciate the help and friendship that the whole Cao group gave me. Finally, I would like to express my gratitude to Dr. Ben Smith for his guidance and help. 4 TABLE OF CONTENTS page ACKNOWLEDGMENTS ...............................................................................................................4 LIST OF FIGURES .........................................................................................................................7 ABSTRACT.....................................................................................................................................9 CHAPTER 1 SEMICONDUCTOR NANOCRYSTALS ............................................................................11 1.1 Introduction..................................................................................................................11
    [Show full text]
  • Why Nature Chose Selenium Hans J
    Reviews pubs.acs.org/acschemicalbiology Why Nature Chose Selenium Hans J. Reich*, ‡ and Robert J. Hondal*,† † University of Vermont, Department of Biochemistry, 89 Beaumont Ave, Given Laboratory, Room B413, Burlington, Vermont 05405, United States ‡ University of WisconsinMadison, Department of Chemistry, 1101 University Avenue, Madison, Wisconsin 53706, United States ABSTRACT: The authors were asked by the Editors of ACS Chemical Biology to write an article titled “Why Nature Chose Selenium” for the occasion of the upcoming bicentennial of the discovery of selenium by the Swedish chemist Jöns Jacob Berzelius in 1817 and styled after the famous work of Frank Westheimer on the biological chemistry of phosphate [Westheimer, F. H. (1987) Why Nature Chose Phosphates, Science 235, 1173−1178]. This work gives a history of the important discoveries of the biological processes that selenium participates in, and a point-by-point comparison of the chemistry of selenium with the atom it replaces in biology, sulfur. This analysis shows that redox chemistry is the largest chemical difference between the two chalcogens. This difference is very large for both one-electron and two-electron redox reactions. Much of this difference is due to the inability of selenium to form π bonds of all types. The outer valence electrons of selenium are also more loosely held than those of sulfur. As a result, selenium is a better nucleophile and will react with reactive oxygen species faster than sulfur, but the resulting lack of π-bond character in the Se−O bond means that the Se-oxide can be much more readily reduced in comparison to S-oxides.
    [Show full text]
  • Biological Chemistry of Hydrogen Selenide
    antioxidants Review Biological Chemistry of Hydrogen Selenide Kellye A. Cupp-Sutton † and Michael T. Ashby *,† Department of Chemistry and Biochemistry, University of Oklahoma, Norman, OK 73019, USA; [email protected] * Correspondence: [email protected]; Tel.: +1-405-325-2924 † These authors contributed equally to this work. Academic Editors: Claus Jacob and Gregory Ian Giles Received: 18 October 2016; Accepted: 8 November 2016; Published: 22 November 2016 Abstract: There are no two main-group elements that exhibit more similar physical and chemical properties than sulfur and selenium. Nonetheless, Nature has deemed both essential for life and has found a way to exploit the subtle unique properties of selenium to include it in biochemistry despite its congener sulfur being 10,000 times more abundant. Selenium is more easily oxidized and it is kinetically more labile, so all selenium compounds could be considered to be “Reactive Selenium Compounds” relative to their sulfur analogues. What is furthermore remarkable is that one of the most reactive forms of selenium, hydrogen selenide (HSe− at physiologic pH), is proposed to be the starting point for the biosynthesis of selenium-containing molecules. This review contrasts the chemical properties of sulfur and selenium and critically assesses the role of hydrogen selenide in biological chemistry. Keywords: biological reactive selenium species; hydrogen selenide; selenocysteine; selenomethionine; selenosugars; selenophosphate; selenocyanate; selenophosphate synthetase thioredoxin reductase 1. Overview of Chalcogens in Biology Chalcogens are the chemical elements in group 16 of the periodic table. This group, which is also known as the oxygen family, consists of the elements oxygen (O), sulfur (S), selenium (Se), tellurium (Te), and the radioactive element polonium (Po).
    [Show full text]
  • Fusion Program
    LA-651 O-PR PROGRESS REPORT 11– UC-21 Issued: November 1976 c. 3 CIC-14 REPORT COLLECTION REPRODUCTION COPY I n = Fusion Program _ .. ~— -- -11 —June 30, 1976 los~alamos scientific laboratory of the University of California LOS ALAMOS, NEW MEXICO 87545 /\ An Afllrmotive Attic.n/Equctl Oppc.rtunity Employer UNITED STATES ENERGY RESEARCH AND DEvELOPMENT ADMINISTRATION CONTRACT W-740 S-ENG. 36 The four most recent reports in this series, unclassified, are LA-5739-PR, LA-59 19-PR, LA-6050-PR, and LA-6245-PR. This work was supported by the (JS Energy Research and Development Adminktra- tion, Division of Laser Fusion. Printed in the United States of Amenea. Availablefrom National Technical Information Service U.S. Department of Commerce 5285 Port Royal Road Springfield, VA 22161 Price: Printed Copy $6.00 Microfiche $3.00 ‘ml, rrp..t m.. prrp.rcd. .caw.t d work.v.mn.rrd b. the t,.imd St.w. (;.v.rnme.t, Wtthw the (,rdwd St.!.s nor !he (’nited.S1-1- K.rre Re... rt h .nd [)...1. tn.nt Ad. mini,t,. tier... or their.mplqtrs. nor..> 0[ theirco.. trwtom. wbw.trwtor.. or their emplu,crs. m.kes ● y w.rr. nlv. .zw.” o, implied.o, .s.umti .nv 1.s.1Ii. hllll, or resw..ihllity rut the.ccur.m. complaenes..or useful.”. of .nw i.r.rm.tio.. .pp.r.t.s. product.or processdlsc!owd.or reprc.eql. th.1 it. would .ot I. fting. prlv. teh ow.rd ,ishl.. CONTENTS Abstract 1 Summary 2 I. C02 Laser Program 10 Single-Beam System (S6S) 10 Two-Beam System (TBS) 12 Eight-Beam Laser System 16 High-Energy Gas Laser Facility (HEGLF) 20 C02 Laser Technology 35 II.
    [Show full text]
  • Assessing Phosphine−Chalcogen Bond Energetics from Calculations Samuel R
    Chemistry Publications Chemistry 2015 Assessing Phosphine−Chalcogen Bond Energetics from Calculations Samuel R. Alvarado Iowa State University Ian A. Shortt Prairie View A & M University Hua-Jun Fan Prairie View A & M University Javier Vela Iowa State University Follow this and additional works at: http://lib.dr.iastate.edu/chem_pubs Part of the Inorganic Chemistry Commons The ompc lete bibliographic information for this item can be found at http://lib.dr.iastate.edu/ chem_pubs/106. For information on how to cite this item, please visit http://lib.dr.iastate.edu/ howtocite.html. This Article is brought to you for free and open access by the Chemistry at Iowa State University Digital Repository. It has been accepted for inclusion in Chemistry Publications by an authorized administrator of Iowa State University Digital Repository. For more information, please contact [email protected]. Assessing Phosphine−Chalcogen Bond Energetics from Calculations Abstract Phosphine chalcogenides are useful reagents in chalcogen atom transfer reactions and nanocrystal syntheses. Understanding the strength and electronic structure of these bonds is key to optimizing their use, but a limited number of experimental and computational studies probe these issues. Using density functional theory (DFT), we computationally screen multiple series of trisubstituted phosphine chalcogenide molecules with a variety of phosphorus substituents and examine how these affect the strength of the phosphorus- chalcogen bond. DFT provides valuable data on these compounds including P-E bond dissociation energies, P-E bond order,Loẅ din charge on phosphorus and chalcogen atoms, and molecular geometries. Experimentally monitoring the 31P and 77Se NMR chemical shifts nda published Hammett onc stants provides good estimates and confirmation of the relative magnitude of electronic shielding around these nuclei and confirms the predictive value of the computational results.
    [Show full text]
  • Self-Assembled Bismuth Selenide (Bi2se3) Quantum Dots Grown by Molecular Beam Epitaxy
    City University of New York (CUNY) CUNY Academic Works Publications and Research City College of New York 2019 Self-assembled Bismuth selenide (Bi2se3) quantum dots grown by molecular beam epitaxy Marcel S. Claro CUNY City College Ido Levy CUNY City College Abhinandan Gangopadhyay Arizona State University David J. Smith Arizona State University Maria C. Tamargo CUNY City College How does access to this work benefit ou?y Let us know! More information about this work at: https://academicworks.cuny.edu/cc_pubs/710 Discover additional works at: https://academicworks.cuny.edu This work is made publicly available by the City University of New York (CUNY). Contact: [email protected] www.nature.com/scientificreports OPEN Self-assembled Bismuth Selenide (Bi2Se3) quantum dots grown by molecular beam epitaxy Received: 5 September 2018 Marcel S. Claro 1,5, Ido Levy1,2, Abhinandan Gangopadhyay3, David J. Smith4 & Accepted: 28 January 2019 Maria C. Tamargo1,2 Published: xx xx xxxx We report the growth of self-assembled Bi2Se3 quantum dots (QDs) by molecular beam epitaxy on GaAs substrates using the droplet epitaxy technique. The QD formation occurs after anneal of Bismuth droplets under Selenium fux. Characterization by atomic force microscopy, scanning electron microscopy, X-ray difraction, high-resolution transmission electron microscopy and X-ray refectance spectroscopy is presented. Raman spectra confrm the QD quality. The quantum dots are crystalline, with hexagonal shape, and have average dimensions of 12-nm height (12 quintuple layers) and 46-nm width, and a density of 8.5 × 109 cm−2. This droplet growth technique provides a means to produce topological insulator QDs in a reproducible and controllable way, providing convenient access to a promising quantum material with singular spin properties.
    [Show full text]
  • Copper-Selenide and Copper-Telluride Composites Powders Sintetized by Ionic Exchange
    Chalcogenide Letters Vol. 11, No. 1, January 2014, p. 13 - 19 COPPER-SELENIDE AND COPPER-TELLURIDE COMPOSITES POWDERS SINTETIZED BY IONIC EXCHANGE O. ARELLANO-TÁNORIa,b, M. C. ACOSTA-ENRÍQUEZa*, R. OCHOA-LANDÍNc, R. IÑIGUEZ-PALOMARESc, T. MENDÍVIL-REYNOSOc,d, M. FLORES-ACOSTAa ,S. J. CASTILLOa aDepartamento de Investigación en Física, Universidad de Sonora, Apdo. Postal 5-088, CP. 83000, Hermosillo, Sonora, México. bInstituto Tecnológico y de Estudios Superiores de Monterrey, Campus Sonora Norte, Blvd. Enrique Mazón López No. 965, C.P. 83000, Hermosillo, Son., México cDepartamento de Física, Universidad de Sonora, Apdo. Postal 1626, CP. 83000 Hermosillo, Sonora, México. dCentro de Investigación en Materiales Avanzados, Miguel de Cervantes 120, Complejo Industrial. CP 31109 Chihuahua, Chih., México. At this research it is provide two precursor solutions of selenium ions (Q’) and tellurium ions (Q) used to success easy ways in order to synthetize composites containing mainly the one copper-selenide (CuSe) and the another copper-telluride (CuTe). By Raman spectroscopy the binary copper selenides chemical composition was detected, while from X-Ray photoelectrons spectroscopy (XPS) were observed the binding energies of Se 3d and Cu 2p3 of 53 eV and 953 eV, respectively. The Copper selenide morphology was investigated by TEM observing particles are aggregated. Also, the absorption spectrum of copper selenide corresponds to direct band gap of 2.79 eV and indirect band gap of 1.36 eV. In the same way, Raman spectroscopy of chemical composition of teineite was detected for CuTe formulation, similarly XPS expose the Te 3d region shows that the valence of Te is -2, while the Cu 3p region show valence for the copper of +1.
    [Show full text]
  • Mercury Stabilization Using Thiosulfate Or Selenosulfate
    MERCURY STABILIZATION USING THIOSULFATE OR SELENOSULFATE by Zizheng Zhou B.A.Sc, The University of British Columbia, 2011 A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF APPLIED SCIENCE in The Faculty of Graduate Studies (Materials Engineering) THE UNIVERSITY OF BRITISH COLUMBIA (Vancouver) April, 2013 © Zizheng Zhou, 2013 ABSTRACT Mercury is often found associated with gold and silver minerals in ore bodies. It is recovered as liquid elemental mercury in several stages including carbon adsorption, carbon elution, electrowinning and retorting. Thus a great amount of mercury is produced as a by-product in gold mines. The Mercury Export Ban Act of 2008 prohibits conveying, selling and distributing elemental mercury by federal agencies in United States. It also bans the export of elemental mercury starting January 1, 2013. As a result, a long-term mercury management plan is required by gold mining companies that generate liquid mercury as a by-product. This thesis will develop a process to effectively convert elemental mercury into much more stable mercury sulfide and mercury selenide for safe disposal. The process consists of 1) extraction of elemental mercury into solution to form aqueous mercury (II) and 2) mercury precipitation as mercury sulfide or mercury selenide. Elemental mercury can be effectively extracted by using hypochlorite solution in acidic environment to form aqueous mercury (II) chloride. The effect of different parameters on the extent and rate of mercury extraction were studied, such as pH, temperature, stirring speed and hypochlorite concentration. Results show that near complete extraction can be achieved within 8 hours by using excess sodium hypochlorite at pH 4 with a fast stirring speed of 1000RPM.
    [Show full text]
  • DIVISION DE CHIMIE DEPARTEMENT DE GENIE RADIOACTIF Service D'hydrométallurgie Et De Chimie Des Transuraniens
    DIVISION DE CHIMIE DEPARTEMENT DE GENIE RADIOACTIF Service d'Hydrométallurgie et de Chimie des Transuraniens CRYSTAL CHEMISTRY OF ACTINIDE PNICTIDES AND CHALCOGENIDES PART OF THE NON-METAL ELEMENT IN THE 5f ELECTRON DELOCALIZATION D.DAMIEN - J. P. CHAR VILLA T - Y.HERY 173. Notional Meeting of the Aaerican Chewicol Society. Nm Orleans, La., USA, 20-25 March 1977 CEA-CONF—3968 Commissariat à l'Energie Atomique Centre d'Etudes Nucléaires de Fontenay-aux-Roses B.P.6 92260 FONTENAY-AUX-ROSES 1. INTRODUCTION We started to study the solid state chemistry of the actinide pnic• tides and chalcogenides in order to compare the properties of 4f and 5f electrons in semi-metallic compounds. In the actinide metals up to pluto• nium, the 5f orbitals take a prominent part in the bonding, leading to physical properties and particularly to crystal structures different from those of the rare-earth metals. On the other hand, ionic compounds, such as halides, have the same crystal structures in both actinide and lanthanide series when the elements have close ionic radii, and exhibit the 4f and 5f contractions respectively. In chalcogenides and pnictides the actinide elements do not make a uniform series since they can form compounds which are diffe• rent in composition and crystal structure as well. Two distinct groups are found : the uranium type compounds, and the rare-earth type compounds including those of plutonium, americium and curium. Neptunium is generally an intermediate element giving both types of compounds so that we shall review first the crystal chemistry of neptunium chalcogenides and pnictides. The repartition of the actinide s into two groups, depends upon the valency state of the actinide element : 4+ cations lead to uranium type chalcogenides and pnictides, while 3+ cations lead to rare-earth type compounds.
    [Show full text]
  • Standard X-Ray Diffraction Powder Patterns
    E^l Admin. NBS MONOGRAPH 25—SECTION 5 Refecii^M not to be ^ferlrom the library. Standard X-ray Diffraction Powder Patterns ^\ / U.S. DEPARTMENT OF COMMERCE S NATIONAL BUREAU OF STANDARDS THE NATIONAL BUREAU OF STANDARDS The National Bureau of Standards^ provides measurement and technical information services essential to the efficiency and effectiveness of the work of the Nation's scientists and engineers. The Bureau serves also as a focal point in the Federal Government for assuring maximum application of the physical and engineering sciences to the advancement of technology in industry and commerce. To accomplish this mission, the Bureau is organized into three institutes covering broad program areas of research and services: THE INSTITUTE FOR BASIC STANDARDS . provides the central basis within the United States for a complete and consistent system of physical measurements, coordinates that system with the measurement systems of other nations, and furnishes essential services leading to accurate and uniform physical measurements throughout the Nation's scientific community, industry, and commerce. This Institute comprises a series of divisions, each serving a classical subject matter area: —Applied Mathematics—Electricity—Metrology—Mechanics—Heat—Atomic Physics—Physical Chemistry—Radiation Physics— -Laboratory Astrophysics^—Radio Standards Laboratory,^ which includes Radio Standards Physics and Radio Standards Engineering—Office of Standard Refer- ence Data. THE INSTITUTE FOR MATERIALS RESEARCH . conducts materials research and provides associated materials services including mainly reference materials and data on the properties of ma- terials. Beyond its direct interest to the Nation's scientists and engineers, this Institute yields services which are essential to the advancement of technology in industry and commerce.
    [Show full text]
  • 15 CFR Ch. VII (1–1–20 Edition) § 774.2
    § 774.2 15 CFR Ch. VII (1–1–20 Edition) for purposes of ECCNs, where a defini- mula (including hydrates) regardless of tion is provided in the ‘‘related defini- name or CAS number. CAS numbers tions’’ paragraph in the License Re- are shown to assist in identifying a quirements section of ECCNs or some- particular chemical or mixture, irre- times in Notes and Technical Notes for spective of nomenclature. CAS num- particular ECCNs and that definition is bers cannot be used as unique identi- specific to that particular ECCN. In fiers because some forms of the listed this sense the quotes are helpful both chemical have different CAS numbers, in the use of single and double quotes, and mixtures containing a listed chem- but a good compliance practice is to fa- ical may also have different CAS num- miliarize yourself with the defined bers. terms in part 772, and when reviewing a [78 FR 61903, Oct. 4, 2013, as amended at 79 FR control parameter on the CCL that 32627, June 5, 2014; 81 FR 64679, Sept. 20, 2016] uses a term that is not in quotes to be aware it may be defined in part 772. It § 774.2 [Reserved] is also a useful compliance practice to review the ‘‘Related Definitions’’ para- SUPPLEMENT NO. 1 TO PART 774—THE graph and Notes and Technical Notes COMMERCE CONTROL LIST to determine if the term is defined for CATEGORY 0—NUCLEAR MATERIALS, FACILI- purposes of a particular ECCN. TIES, AND EQUIPMENT [AND MISCELLANEOUS (1) Use of double quotes. If a term on ITEMS] the CCL uses double quotes it means there is a defined term in part 772.
    [Show full text]
  • Selenium in the Environment, Metabolism and Involvement in Body Functions
    Molecules 2013, 18, 3292-3311; doi:10.3390/molecules18033292 OPEN ACCESS molecules ISSN 1420-3049 www.mdpi.com/journal/molecules Review Selenium in the Environment, Metabolism and Involvement in Body Functions Youcef Mehdi 1, Jean-Luc Hornick 1, Louis Istasse 1 and Isabelle Dufrasne 2,* 1 ULg-FMV, Nutrition Unit, Department of Animal Production, Boulevard de Colonster 20, Bât. B43 4000, Liège, Belgium; E-Mails: [email protected] (Y.M.); [email protected] (J.-L.H.); [email protected] (L.I.) 2 ULg-FMV, Station Expérimentale Chemin de la Ferme 6, Bât. B39 4000, Liège, Belgium * Author to whom correspondence should be addressed; E-Mail: [email protected]; Tel.: +32-4-366-2373; Fax: +32-4-366-4733. Received: 3 December 2012; in revised form: 5 March 2013 / Accepted: 7 March 2013 / Published: 13 March 2013 34 Abstract: Selenium (Se79 ) is a metalloid which is close to sulfur (S) in terms of properties. The Se concentration in soil varies with type, texture and organic matter content of the soil and with rainfall. Its assimilation by plants is influenced by the physico-chemical properties of the soil (redox status, pH and microbial activity). The presence of Se in the atmosphere is linked to natural and anthropogenic activities. Selenoproteins, in which selenium is present as selenocysteine, present an important role in many body functions, such as antioxidant defense and the formation of thyroid hormones. Some selenoprotein metabolites play a role in cancer prevention. In the immune system, selenium stimulates antibody formation and activity of helper T cells, cytotoxic T cells and Natural Killer (NK) cells.
    [Show full text]