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Dr. Claude Musikas
9 March 2006
1130 AM
CHE 101
Chemical
separation of the minor actinides from the high level wastes: Recent
research in the EC
This lecture is a review of the
chemical researches undertaken in one EC program for the separations of the
minor actinides contained in the high level wastes coming from the first
cycle of the spent nuclear fuel reprocessing, using the Purex process.
Solvent extraction has been chosen and actually processes in two steps have
been investigated.
Step A)
The separation of the minor actinides from the HLR (high level raffinate)
directly after the extraction of U and Pu by the Purex process or after the
concentration-denitration of the HLR and high level concentrate (HLC). The
difference between the two options is the much higher concentrations of the
fission products in the HLC which necessitates different flow sheets for the
counter currents separations. For steps A, the optimization of the
malonamides formula has been achieved considering the Am (III) extraction,
the third phase boundaries with HNO3, Nd(III) and U(VI), and the
stability of the malonamide to hydrolysis and radiolysis. After step A one
concentrate of actinide (III) plus lanthanide (III) in 0.5 N is obtained and
might serve as the feed of step B.
Step B)
The trivalent actinides-lanthanides
group separation. Various nitrogen donors
extractants have been synthesized and among them some bis triazine
pyridine(BTP) show factor of separation Am(III)- Eu(III) close to 1000 .BTP
extract efficiently Am(III) from 1N HNO3 without the presence of
synergists. However because of their poor chemical stability they cannot be
used in counter current separations. The sulphur donor extractant (bis
chlorophenyl dithophosphoric acids HDDTP) also give separation factors
greater than 1000 in test tubes essays and extracts efficiently Am(III) from
0.5N HNO3; but as the BTP it is insufficiently stable to be used
in counter–current separations.
The formula of the species of the
actinides and lanthanides in organic phases containing HDDTP plus a neutral
oxygen donor organophosphoric extractant are different for the actinides and
the lanthanides. The differences in the formulas show a higher affinity of
the actinides for the sulphur donor. This could be attributed to the higher
covalent interactions of the actinides with the sulphur. Such higher
interactions are also indicated by the EXAFS spectra .of the organic phases.
Thursday 23 February 2006
11:30 AM
CHE
101
Title: Molten Salt Processing of High Level
Waste Oxides:
Metal Oxide Redox and Thermal H2
Production in Molten NaOH
Stephen F. Agnew
Chemistry and Materials
Nuclear Waste Consulting
San Diego, CA
sfagnew@san.rr.com
Abstract
Molten salt baths have long been recognized as useful for various waste
processing applications. Much work has been done in the past with molten
oxidizing sodium carbonate for example, as well as with molten metal
chloride and fluoride baths.
Archimedes Technology Group, LLC, has developed a molten sodium hydroxide (mNaOH)
process for processing Hanford high-level waste and has shown its viability
at a pilot scale with surrogate wastes. Molten sodium hydroxide has many
interesting properties compared with other molten salts and, of course, has
a traditional use in caustic “fusions” for chemical assay and synthesis. It
has a relatively low melting point, 323 C, and a very wide liquid range, up
to 1328 C. The mNaOH is continuously miscible with water over a wide
temperature range, ambient to ~180 C, it has an acid/base chemistry
controlled by its water vapor pressure, and its redox potential is
controlled by either H2 or O2 vapor pressures. Since mNaOH is
relatively non-complexing, its chemistry is similar to a “high-temperature”
form of water.
The dissociative equilibrium of molten NaOH is entirely analogous to the
dissociation of pure water and leads to either “acidic” or “basic” melts and
the definition of pH2O. Instead of protons for increasing
acidity, increasing water vapor pressure over mNaOH increases its acidity
and instead of hydroxide for increasing basicity, mNaOH basicity increases
upon addition of sodium oxide (or indeed any oxide).
What makes mNaOH especially interesting, though, is the ease with which its
redox state can be controlled. The higher temperatures of mNaOH mean that
the very simple reducing agent, H2, or oxidizing agent O2,
result in thermodynamic redox potentials in the melt that are the same as
sodium metal or peroxide, respectively.
Coupling these characteristics to the large NaOH liquid temperature range
suggests applying mNaOH not only to waste oxide treatment, but also to
thermal hydrogen production. In fact, we have already observed hydrogen
production from mNaOH with several different metals. The very corrosive
nature of these melts has meant that much of our effort has been associated
with developing appropriate materials for handling and piping. Metal oxide
transformations, their characterizations, and technological handling
techniques will all be discussed, especially as it relates to treating HLW
and spent fuel oxides.
Monday November 28 2005
1 p.m.
Marjorie Barrick
Auditorium
David A. Costa
Nuclear Materials Technology Division
Los Alamos National Laboratory
Seminar Title: Actinide Chemistry in Room
Temperature Ionic Liquids
Room temperature ionic liquids (RTILs) offer great potential for
development of efficient, environmentally benign purification and
processing schemes for nuclear materials. Ionic liquids composed of
quaternary ammonium cations combined with the weakly coordinating
N(SO2CF3)2 anion, along with the more familiar chloroaluminate melts,
will be examined. This talk will focus on two aspects of our studies of
actinide chemistry in ionic liquids. First, the chemical design and
synthesis of ionic liquids that are compatible with highly
electropositive actinide metals is outlined, including the relationship
between chemical composition (choice of anion and cation) and ionic
liquid physical properties. An important goal of this research is the
development of robust, highly conductive solvents that will enable
electrochemical control of actinide oxidation states, including direct
access of the zero valent metals (electroplating). The second aspect to
be considered is our effort to understand the chemical properties of
metal complexes dissolved in these novel media. Our initial work has
focused on the behavior of simple uranium species. Of special interest
is the relationship between the metal’s primary coordination sphere and
its electrochemical behavior. Recent results that address the
fundamental interaction between electrophilic metal ions and ionic
liquid solvents will also be highlighted.
Wednesday 16 November 2005
12 PM
Marjorie Barrick Auditorium
Dr. Gordon D. Jarvinen
Associate Director,
G.T. Seaborg Institute,
Los Alamos National Laboratory
Seminar Title: Separations Technology for
Advanced Nuclear Fuel Cycles
A key part of any fission-based fuel cycle other than the
once-through cycle is the separations technology needed to partition the
fissile and fertile components of the used fuel from the fission
products. Presently, the only technology used worldwide at a significant
level to separate the components of spent nuclear fuel is the PUREX
process. In the U.S. the Advanced Fuel Cycle Initiative (AFCI) was
established with the vision of enabling sustainable nuclear energy
production by developing state-of-the art technologies for closing the
nuclear fuel cycle. A brief overview of the AFCI separations program
will be presented. Under the AFCI separations development efforts, a
team at Los Alamos is evaluating the crystallization of uranyl nitrate
from nitric acid solution as a more efficient way of separating uranium
from dissolved spent fuel. The use of alkaline solutions for dissolution
and separation of the components of spent fuel is also being examined
and preliminary work in this area will be described.
Tuesday 4 October 2005
CBC C138
4:00-5:00 PM
Dr. Martine Duff
Savannah River National Laboratory
Seminar title:
Applications of XAFS Spectroscopic Techniques to Problems Associated
with Nuclear Waste
XAFS spectroscopy is used to determine
the oxidation state and chemical form of elements under a wide range of
conditions. XAFS spectroscopy is
well suited to investigations of actinide elements and other
radionuclides. Research
highlighting the role of XAFS spectroscopy in nuclear waste studies is
presented.
Friday 18 March 2005
CHE 101
3:30-4:40 PM
Dr. Ken Moody
Lawrence Livermore National Laboratory
Seminar title: Nuclear forensic radiochemistry
Signatures inherent in samples of uranium and plutonium give clues about the origin of the material. Such information can be quite important when trying to determine the source of smuggled nuclear materials interdicted by law enforcement personnel. The fact that significant amounts of illicit weapons-grade materials have been seized in Europe attests to the importance of this problem. In-growth of protactinium, thorium and radium daughters provides several independent chronometers from which the date of the last chemical separation can be determined. Excesses of a given radionuclide over the amount produced by radioactive decay give clues to the chemical processes used in manufacturing the sample, while the abundances of the isotopes of the matrix give information on the previous relationship between the production facility and the fuel cycle. Inorganic contaminants and alloy compositions provide use information. Results obtained from several real-world samples will be used to illustrate these points.
Friday 4 March 2005
Dr. Patricia Paviet-Hartmannp
Framatome ANP, Inc.
The life cycle of nuclear waste: from their generation to their final disposal
The worldwide operating uranium fueled reactors produce 400 GW electric energy and by 2010 more than 300,000 tons of spent nuclear fuel will need to be either disposed of in deep geological formations or treated before their final disposal. In France, e.g., a Purex-based process on solvent extraction with tributyl phosphate (TBP) is applied for reprocessing spent nuclear fuel separating U(VI) and Pu(IV) from the high level radioactive liquor. On the other hand, in the USA, the aqueous polishing (AP) process - also a Purex-based solvent extraction process - will be applied to purify weapon grade plutonium in order to produce MOX fuel in the near future. This presentation will provide an overview on the nuclear fuel cycle and is addressing the following topics:
- The Purex process and its highly radioactive liquid waste stream.
- The fission product 99Tc in radioactive liquid wastes, and the selective extraction of 99Tc by crown-ethers from ILW.
- Introduction on nuclear waste-forms.
- An overview of repository science.
A significant criterion in evaluating disposal strategies for nuclear waste is the assessment of the isolation capacity for the most radiotoxic radionuclides, the actinides. The associated risk of the disposal of nuclear waste depends not only on the amount of radioactive elements stored in the repository but also on whether these elements can be mobilized. Some data on the solution chemistry and behavior of Plutonium and Uranium in groundwater and chloride solutions will be presented and the production and interaction of radiolysis by-products with actinides will be discussed.
Thursday 3 March 2005
Dr. Al Sattelberger
Los Alamos National Laboratory
Inorganic and Organometallic Chemistry at Los Alamos National Laboratory: Having Fun in a Physics Laboratory
The presentation covers the research range and interests of the Chemistry Division at Los Alamos. In particular, this presentation presents research performed on actinide separations, coordination and organometallic chemistry, technetium chemistry, multiple metal-metal bonding, transition metal allyl chemistry, and catalysis.
Friday 25 February 2005
Glenn A. Fugate
Department of Environmental Engineering & Sciences, Clemson University
Structural Effects on the Coordination Chemistry of Aminopolycarboxylate Ligands and the f-Elements
Aminopolycarboxylate ligands are an important class of compounds in the processing, separations and waste chemistries of the f-elements. Variations in the structure of these compounds can alter their coordination chemistry when compared to compounds with similar coordination sites. The lanthanide coordination chemistry of piperidine ring based compounds (piperidine-2,6-dicarboxylic acid and 2,6-dicarboxypiperidine-N-acetic acid) and chelidamic acid will be compared to straight chain compounds (iminodiacetic acid and nitrilotriacetic acid) and dipicolinic acid, respectively.
Work on depth profile determination of cesium-137 contamination will also be presented. Recent work has examined several techniques for the determination of depth profiles of radioactive materials in construction materials. The material ranges and measurement resolutions were determined for two non-destructive spectroscopy methods for aluminum and cesium-137.
Friday 18 February 2005
A.J. Francis
Brookhaven National Laboratory
Interaction of Microbes with Heavy Metals
The presence of actinides (U, Np, Pu, Am) and organic and inorganic compounds (cellulose, chelating agents, plastics, nitrate and sulphate) in transuranic (TRU) and mixed wastes is a major concern because of their potential for migration from the waste repositories. Microorganisms have been detected in TRU wastes, Pu-contaminated soils, low-level radioactive wastes, backfill materials, natural analogue sites, and waste-repository sites slated for high-level wastes. Significant aerobic and anaerobic microbial activity is expected in the waste because of the presence of electron donors and acceptors. Biodegradation of the TRU waste can result in gas generation and pressurization of containment areas, waste volume reduction, and subsidence in the repository. Microbial corrosion of the waste canisters can compromise waste integrity. The actinides exist in various oxidation states and may be present as oxide, coprecipitates, inorganic, and organic complexes. Microorganisms by direct enzymatic or indirect non-enzymatic actions could affect the chemical nature of the actinides by altering the speciation, solubility, and sorption properties. Free-living bacteria suspended in the groundwater fall within the colloidal size range and have a strong affinity for actinides, giving them the potential to transport radionuclides. Microbial transformations of various chemical forms of U and Pu commonly present in TRU and mixed wastes and contaminated soils will be discussed. Fundamental understanding of the microbial transformations of radionuclides under various microbial process and environmental conditions will be useful in developing appropriate waste treatment, remediation and long-tem management strategies as well as predicting the microbial impacts on the performance of the waste sites.
Monday 8 November 2004
- Professor Jacques Foos, Director Nuclear Science
Conservatoire national des arts et métiers
- Professor Micheline Draye
Laboratoire de Chimie Moleculaire et Environnement
Universite de Savoie – ESIGEC
- Ecole Nationale Superieure de Chimie de Paris
Laboratoire d'Electrochimie et de Chimie Analytique
Groupe Procedes de Separation et Radiochimie
Radiation effect on ligands used in the extraction of radionuclides
- Professor Jean-Louis Nigon
COGEMA
Presentation: World Nuclear University and radiochemistry education
Friday 24 September 2004
Dawn A. Shaughnessy
Chemical Biology and Nuclear Science Division
Chemistry and Materials Science Directorate
Lawrence Livermore National Laboratory
The LLNL Heavy Element Program – New Elements and New Chemistry
Abstract: The heavy element group at Lawrence Livermore National Laboratory (LLNL) has had a long tradition of nuclear and radiochemistry dating back to the 1950’s. Some of the most exciting work has taken place in the last five years (in collaboration with the Flerov Laboratory of Nuclear Reactions in Dubna, Russia) with the discovery of four new elements - 113, 114, 115, and 116. By pushing the boundaries of the periodic table, we can start to answer some of the most fundamental questions of nuclear science, such as the locations of the next “magic numbers” of protons and neutrons, and the possibility of an “Island of Stability” where nuclides would have lifetimes much longer than those currently observed in the heaviest elements. We have already seen evidence of extra-stability in the heaviest nuclides, which leads to half-lives that are long enough for us to perform chemistry on these isotopes one atom at a time. Work is already underway on developing a chemical system designed to isolate element 114. These experiments will allow nuclear chemists to accurately identify the chemical properties of element 114 and determine whether or not it truly behaves as a Group 14 element such as Sn or Pb. In this presentation, a brief history of the discovery of these new elements will be given as well as an introduction to the chemical experiments in progress.
Dr. Shaughnessy obtained her Ph.D. in Nuclear Chemistry from the University of California, Berkeley, in 1999. She has been at LLNL as a member of the Analytical and Nuclear Chemistry Division in the Stockpile Radiochemistry Group since August of 2002. Her research interests include synthesis and study of the nuclear and chemical properties of the actinide and trans-actinide elements, spontaneous and delayed fission properties, nuclear reaction cross-section measurements, actinide target preparation, radiochemical separation techniques, and the behavior of radioactive contaminants in the environment.
Friday 17 September 2004, 3:30 PM
Prof. Dr. Thomas Fanghänel, Director Institut für Nukleare Entsorgung (INE)
Forschungszentrum Karlsruhe
Interaction of actinides with mineral surfaces
Professor Fanghaenel has been the director of the Institute für Nukleare Entsorgung (Institute for Nuclear Waste Disposal) at Forschungszentrum Karlsruhe and a Professor at the University of Heidelberg, Chair of Radiochemistry since 2002. He was the Director of the Institute of Radiochemistry at Forschungszentrum Rossendorf and Professor at the Technical University Dresden, Chair of Radiochemistry, from 2000-2002. His research interests include basic and applied research on the behavior of radionuclides/actinides in the geosphere, aquatic chemistry and thermodynamics of actinides and fission products, aqueous/mineral interfaces interactions of actinides, and long-term safety of nuclear waste disposal.
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