Preparation of americium targets for nuclear chemistry experiments at DANCE

Using 1 gram of ²⁴¹Am from LANL stocks, the purification steps required to obtain a solution of ²⁴¹Am from the original material are described. Part of the purified solution was submitted for purity analysis by mass spectrometry, radiochemistry and trace metals analysis. The impurities were expected to be ²³⁹Pu and ²³⁷Np. A second fraction of this material was used for electroplating three samples onto titanium disks that were suitable for insertion into an instrument package to be placed into the DANCE detector. The purification methods used, the electroplating setup and the solutions to various problems that were encountered in making these targets are discussed. The analytical results are discussed as well as the yields from the electrodeposition process. Comparison of these yields with those from similar experiments utilizing ²³⁵U and ²⁴³Am are also discussed.     

Preparation and characterization of strontium targets for nuclear astrophysics experiments

Journal of Radioanalytical and Nuclear Chemistry - The present paper describes preparation and characterization of strontium targets for nuclear astrophysical experiments with alpha particles...     

Preparation of a one-curie <Superscript>171</Superscript>Tm target for the detector for advanced neutron capture experiments (DANCE)

Approximately one curie of ¹⁷¹Tm (T _1/2 = 1.92a) has been produced and purified for the purpose of making a nuclear target for the first measurements of its neutron capture cross section. Target preparation consisted of three key steps: (1) material production; (2) separation and purification; and (3) electrodeposition onto a suitable backing material. Approximately 1.5 mg of the target material (at the time of separation) was produced by irradiating ca. 250 mg of its stable enriched ¹⁷⁰Er lanthanide neighbour with neutrons at the ILL reactor in France. This production method resulted in a “difficult-to-separate” 1:167 mixture of near-neighboring lanthanides, Tm and Er. Separation and purification was accomplished using high-performance liquid chromatography (HPLC), with a proprietary cation-exchange column (Dionex, CS-3) and alpha-hydroxyisobutyric acid (α-HIB) eluent. This technique yielded a final product of ∼95% purity with respect to Tm. A portion (20 μg) of the Tm was electrodeposited onto thin Be foil and delivered to the Los Alamos Neutron Science Center (LANSCE) for preliminary analysis of its neutron capture cross section using the Detector for Advanced Neutron Capture Experiments (DANCE). This paper discusses the major hurdles associated with the separation and purification step, including scale-up issues related to the use of HPLC for material separation and purification of the target material from α-HIB and 4-(2-pyridylazo)resorcinol (PAR) colorant.     

Detectors for high energy nuclear physics experiments

High energy nuclear physics experiments started about a decade ago with the aim of studying quark gluon plasmas (QGP) in the laboratory. Statistical QCD predicts that in nuclear collisions at ultra-relativistic energies the quarks and gluons in hadrons will be momentarily deconfined into a phase of matter containing free quarks and gluons in the form of a plasma. This quark gluon plasma is also thought to have existed in the very early history of the evolution of the Universe, some 10 microseconds after the Big Bang when the extremely hot blob of energy started to cool and be converted into matter. Thus the study of ultra-relativistic nuclear collisions is important from the point of view of nuclear and high energy physics, astrophysics and cosmology. In these studies new detectors are required.     

Analytical chemistry in nuclear technology

Summary The objectives of analytical chemistry in nuclear technology are discussed. The analytical techniques and methods commonly used in the various phases of the nuclear fuel cycle, mining and fuel fabrication, reprocessing and nuclear waste management are described and their advantages and disadvantages are demonstrated. The question of applying in-line analytical instruments in this area is addressed and some techniques which show a proven potential for such an employment are defined.Presented at the 33rd IUPAC Congress, Budapest, August 17–22, 1991.     

Preparation of isotopic antimony targets

Thin self-supporting ¹²³Sb targets were needed for studies using GAMMASPHERE investigating transverse wobbling in the highly-deformed triaxial nucleus ¹³⁵Pr. The experiment was carried out using the ¹²³Sb(¹⁶O,4n)¹³⁵Pr reaction with the 80 MeV ¹⁶O beam provided by the ATLAS accelerator facility. In particle–particle coincidence measurements ¹²¹Sb targets were irradiated with a 332 MeV ²⁸Si beam from ATLAS to measure evaporation residues and fission. The antimony targets were prepared self-supporting by the method of physical vapor deposition onto polished glass substrates or on various backing materials. Target thicknesses on the order of 500–1,000 μg/cm² were obtained and used for the experiments. Details of the target production and performance in beam will be discussed.     

Preparation of azidoaryl- and azidoalkyloxazoles for click chemistry

A series of azidoaryl- and azidoalkyl(diphenyl)oxazole scaffolds were warranted for biofilm inhibition studies. Cyclization of azidoaryl- or azidoalkyl esters of benzoin with ammonium acetate in acetic acid gives 2-azidoaryl- or 2-azidoalkyl-4,5-diphenyloxazoles. The azidoaryl esters are prepared from the corresponding azidocarboxylic acids/acid chlorides while the azidoalkyl esters are prepared from the corresponding haloalkyl esters.     

Uses of pH electrodes in nuclear chemistry

The determination and definition of pH is a controversial subject in many areas in chemistry. For these reasons the International Union of Pure and Applied Chemistry (IUPAC) has developed recommendations for pH measurement. These recommendations are currently (winter 2001) under revision - there will be increased emphasis on traceability of uncertainties in pH measurement. Here we describe how glass electrodes designed for measurement of pH are used in nuclear chemistry. The use of pH electrodes is then related to the IUPAC recommendations. In applied chemistry, e.g. nuclear chemistry, a pH is not sought as often as a hydrogen ion concentration or a simple equilibrium point during a titration. Ionic strengths are, moreover, often above the range in which the IUPAC recommendations apply. In these instances uncertainties must be assessed individually.     

Microcomputer based chemistry experiments – an American perspective

This paper briefly discusses the use of microcomputers for data acquisition and analysis in general chemistry education in the United States. Aspects of successful MBL (Microcomputer Based Laboratory) software development, its present status, and future trends are included.     

Preparation of polymer-bound pyrazolone active esters for combinatorial chemistry

The preparation of solid-phase active esters from a new pyrazolone linker resin is described. N-Acylation using this resin provides various amide products with a high conversion rate and good purity under mild conditions. The polymer-bound pyrazolone linkers are stable in the reaction conditions and are resistant to hydrolysis. Moreover, this resin can also be reused repeatedly without a loss of reactivity.     

An ideal teaching program of nuclear chemistry in the undergraduate chemistry curriculum

It is well known that several reports on the common educational problems of nuclear chemistry have been prepared by certain groups of experts from time to time. According to very important statements in these reports, nuclear chemistry and related courses generally do not take sufficient importance in undergraduate chemistry curricula and it was generally proposed that nuclear chemistry and related courses should be introduced into undergraduate chemistry curricula at universities worldwide. Starting from these statements, an ideal program in an undergraduate chemistry curriculum was proposed to be introduced into the undergraduate chemistry program at the Department of Chemistry, Ege University, in Izmir, Turkey during the regular updating of the chemistry curriculum. Thus, it has been believed that this Department of Chemistry has recently gained an ideal teaching program in the field of nuclear chemistry and its applications in scientific, industrial, and medical sectors. In this contribution, the details of this program will be discussed.     

Preparation of radioactive rare earth targets for neutron capture study

Summary The neutron capture behavior of certain radioactive rare earth nuclides, among them ¹⁷¹Tm and ¹⁵¹Sm, is of interest for astrophysical reasons and for the interpretation of radiochemical data from underground nuclear tests. In order to measure neutron capture excitation functions for these radionuclides, targets were produced that met stringent requirements. This paper describes the purification chemistry and target preparation methods that were employed in order to deliver appropriate samples for study.     

Radiation chemistry and the nuclear fuel cycle

A global collaboration is currently developing solvent extraction separations for the nuclear fuel cycle of the future. The goal is to recover fissionable material for recycle, mitigate proliferation concerns, and mitigate the environmental impact of nuclear waste disposal. Relying on selective metal complexing agents, the radiation stability of these solvent extraction ligands will determine the efficiency and recycle lifetime of any solvent intended for use in this high-radiation environment. This paper reviews work at the Idaho National Laboratory regarding the radiation chemistry of nuclear solvent extraction ligands, with particular emphasis on the reactions of nitrogen-centered radicals.     

Host-guest chemistry at interface for photoswitchable bioelectrocatalysis

Photoswitchable bioelectrocatalysis of glucose with glucose oxidase in an "On-Off" state is fabricated from host-guest chemistry at an interface by using the photocontrolled reversible immobilization and detachment of ferrocene-labeled redox-polymer as mediator.     

Preparation and chemistry of phosphoranyl-derived iodanes

The preparation and chemistry of novel phosphoranyl-derived lambda(3)-iodanes is reported. The phosphoranyl-derived phenyliodonium sulfonates were prepared in good yields by the reaction of stabilized phosphonium ylides [1-triphenylphosphoranylidene-2-propanone, methyl(triphenylphosphoranylidene)acetate, (triphenylphosphoranylidene)acetaldehyde, and (triphenylphosphoranylidene)acetonitrile] with the pyridinium complex of iodobenzene ditriflate or with [hydroxy(tosyloxy)iodo]benzene under mild conditions. These compounds represent a potentially useful class of reagents that combine in one molecule synthetic advantages of a phosphonium ylide and an iodonium salt. Specifically, phosphorane-derived phenyliodonium tosylates can react with soft nucleophiles, such as iodide, bromide, benzenesulfinate, and thiophenolate anions, with a selective formation of the respective alpha-functionalized phosphonium ylides, which can be further converted to alkenes by the Wittig reaction with benzaldehyde. The phosphoranyl-derived benziodoxoles can be prepared by the reaction of 1-acetoxybenziodoxole with stabilized phosphonium ylides. An unusual ligand exchange on the iodine(III) center resulting in the substitution of a carbon ligand with an oxygen ligand was observed in the reaction of these compounds with strong acids.     

The role of NAA in nuclear chemistry education

One of the missions of our Institute is the promotion of basic nuclear teaching for students as well as professional teaching for workers in nuclear industry and research. For nuclear chemistry education, we present here a one day teaching course on radioactive decay and nuclear reactions, and a two or three days course based on reactor irradiation of uranium oxide, instrumental and radiochemical analysis of fission products. In the first experiment, the neutron capture is presented as an example of nuclear reaction; the neutron activation of a silver coin with a Am-Be neutron source, followed by γ-ray spectrometry, is used to identify three radionuclides of silver and to calculate their half-lives. In the second experiment, our teaching reactor is used as a neutron source with a flux about 10¹⁰ n·cm⁻²·s⁻¹ at a low thermal power (10 kW). This low flux allows us to irradiate a small uranium sample which is usable for spectrometry after a short cooling time of about two hours. The first day is reserved for instrumental analysis of the fission products and a second day for the radiochemical separation of a fission radionuclides. With these experimental results, the students have to calculate the number of fissions in the irradiated sample. On optional third day for postgraduate students is devoted to the presentation of NAA and some applications as uranium determination by the fission product spectrometry.