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Aluminum effect on dissolution and precipitation under hyperalkaline conditions: I. Liquid phase transformations.

Substantial amounts of self-boiling, Al-rich, hyperalkaline, and saline high-level waste fluids (HLWF) were deposited to the vadose zone at the Hanford Site, in Washington State. The objective of this study was to investigate the effects of similar fluids on the extent of dissolution and precipitation in the sediments. Metal- and glass-free systems were used to conduct batch experiments at 323 K under CO2 and O2 free conditions. Base-induced dissolution of the soil minerals was rapid in the first 48 h as indicated by immediate releases of Si and Fe into the soil solution. Potassium release lagged behind and dissolution of K-bearing minerals (mica and K-feldspar) proceeded faster only after 2 to 3 d of the experiment. Silicon and Fe release exhibited high dependence on aqueous [Al] (rate orders <-1), because Al decreased free OH concentration in the contact solution and probably inhibited soil mineral dissolution. Initial K release exhibited low dependence on [Al] (fractional rate orders). Initial dissolution rates calculated based on Si release varied with aqueous [Al] from 29.47 to 4.35 x 10(-12) mol m(-2) s(-1). Aluminum participated in the formation of the secondary phases (precipitation rates of 10(-8) mol s(-1)) but the overall precipitation rate of alumino-silicate secondary phases was probably controlled by aqueous [Si] (rates of 10(-9), and rate constants between 0.0054 and 0.0084 h(-1)). The changes in the soil solution chemistry (release of K, Si, Fe, and other elements) may play a significant role in the fate of radionuclides and contaminants like Cs, Sr, Cr, and U in the Hanford sediments.

Accidents↗

[Synthesis of tumor affinity label Yb-169- and Y-90- porphyrin complexes and animal experimental investigations with various Yb-169-porphyrins].

AIM: It should be shown, that it is possible to insert radioactive isotopes of Yb and Y into some selected porphyrins. Besides, first informations about the biodistribution of Yb-169-por-phyrin-complexes should be obtained. METHODS: Carrier added radioactive isotopes were used for the synthesis of the metal porphyrin complexes. The animal experiments were done with mamma carcinoma bearing mice. The activity of the organs was determined 5 and 24 h after i.v. injection in a well counter. RESULTS: Four Yb-169-porphyrin complexes and Y-90-porphyrin complexes could be synthesized in non-carrier-free form. This was verified by absorption spectra, TLC and HPLC. Depending on the complex, the average tumour/background ratios were between 2 and 20. CONCLUSION: The synthesized radioactive metal-porphyrin complexes showed a clear tumour-affinity which could be used for tumour scintigraphy or perhaps therapy if the synthesis is improved (goal: reduction of carrier, other radionuclides).

Animals↗

Tropolone: a lipid solubilizing agent for cationic metals.

Lipid soluble agents which chelate radioactive cations have several potential uses in nuclear medicine including: brain imaging, labeling of blood elements, and identifying fatty infiltration of organs. A tropolone-gallium complex has been characterized by the determination of in vitro partition ratios correlated with in vivo organ distribution in the rat. Partition ratios were determined for gallium-67 citrate, indium-114m chloride, and iron-59 chloride cations complexed with tropolone in chloroform + water, octanol + water, olive oil + water, and olive oil + plasma two-phased systems. Tropolone proved to be highly effective in the lipid solubilization of these metal cations. Distribution studies in animals of these cations complexed with tropolone demonstrated an increased concentration of these cation complexes in tissues of high lipid content when compared with appropriate controls.

Animals↗

Differential effect of N-acetylcysteine on excretion of the metals Hg, Cd, Pb and Au.

Male Wistar rats were subacutely treated with sublethal doses of HgCl2, CdCl2, Pb(NO3)2, or Na-aurothiomalate. The metal preparations contained trace doses of radioactive nuclide. Based on the doses given and on the radioactivity excretion in urine and faeces the body burden was determined. After the metal treatment periods, some of the animals received N-acetylcysteine (up to 100 mg/kg daily, on 6 consecutive days, i.p.), and the effect of this potential chelator on metal excretion was monitored. The excretion of Hg (after dosing with HgCl2) was not influenced by N-acetylcysteine. The elimination of Cd in urine (after dosing with CdCl2) was increased by a factor of four. Also, the elimination of Pb [after dosing with Pb(NO3)2] was gradually increased (in faeces and urine) by increasing doses of N-acetylcysteine. After dosing with Na-aurothiomalate, the excretion of Au in urine was increased to about 30%. The data suggest some activity of N-acetylcysteine in facilitating excretion of Pb, Cd or Au, but not of Hg.

Acetylcysteine↗

Metallic contamination of bone during drilling procedures.

The influence of drills and burs of different shapes and materials on the amount of metallic transfer was studied. In these experiments, holes were drilled in bone with radioactive tools and the amount of metal transferred to the bone was measured by means of gamma-ray spectrometry. The proportion of the drill material transferred to the bone varied widely, depending on the type of the drill, its previous usage, and on the specific element considered. Most of the drills transfer a few microgram of iron to the bone, together with smaller quantities of cobalt, tungsten, and chromium. The total quantity of material transferred to the bone from new drills exceeded that of old drills. Almost invariably, the second drilling transferred less material than did the first, even with used drills.

Animals↗

The Co2+ Adsorption Properties of Al2O3, Fe2O3, Fe3O4, TiO2, and MnO2 Evaluated by Modeling with the Frumkin Isotherm

Adsorption of Co(II) ions on metal oxides is related to radioactive 60Co(II) (de)contamination of nuclear power plants, Co(II) ion retention in soils as a plant nutrient, concentration of Co(II) in deep-sea manganese nodules, and other applications. Here, the amount of adsorbed Co(II) on metal oxides was measured as a function of the pH and concentration of Co(II) ions, and the adsorption properties of metal oxides were evaluated with a model that considers simultaneous (1:1) and (1:2) exchange reactions between Co2+ aqua ions and surface hydroxyl protons obeying the Frumkin isotherm. The possibility of participation of mono- and polynuclear Co(II) hydroxo complexes in the adsorption was examined, and it was suggested that these species play no role under the conditions here. From the model parameters, it was found that the Co2+ adsorption ability of metal oxides increases in the order Al2O3 < Fe2O3 < TiO2 < Fe3O4 < MnO2, showing a good correlation to the electronegativity Xi of the lattice metal ions of the oxides. The Co2+ adsorption was divided into two processes: (1) deprotonation of surface hydroxyl sites and (2) bonding of Co2+ to the deprotonated sites with a negative charge. With increasing Xi, process 1 increases possibly due to the decrease in the donor electron density responsible for covalent bonds with protons, while process 2 changes only slightly. It was suggested that process 2 is due to ionic bond formation ("electrostatic contact adsorption"), which is independent of the donor electron density, and the correlation of the overall process to Xi found here was ascribed to process 1 above. Copyright 1997 Academic Press. Copyright 1997Academic Press

Journal Article↗

Penetration of tritium (as tritiated water vapour) into low carbon steel and remediation using abrasive cleaning.

The UKAEA Winfrith site is in a phase of accelerated decommissioning and de-licensing which will generate significant volumes of metal wastes some of which may be suitable for disposal as exempt wastes. If contamination is present, it is often confined within the surface layers of the metal. The UKAEA Winfrith site operates a shot-blast facility (WACM) that removes paint and surface contamination from low carbon steel enabling surface contaminated painted metal to be processed and therefore certified as exempt. A study was conducted to determine whether tritium (as tritiated water vapour) has penetrated into the metal to levels exceeding the Radioactive Substances Act (1993), Substances of Low Activity (SoLA) Exemption Order criteria, and whether processing via the WACM removes sufficient tritium contamination that the SoLA Exemption Order criteria can be met. The results of sampling and analysis show that the tritium is mainly held in the paint or outer 40 microm layer of the metal and that processing through the WACM removes these layers along with sufficient tritium to meet the SoLA Exemption Order criteria.

Carbon↗

Pioneers of nuclear medicine, Madame Curie.

Among those who have made important discoveries in the field of radioactivity and thus helped in the development of nuclear medicine as an identical entity are: Heinrich Hertz who in 1886 demonstrated the existence of radiowaves. In 1895 Wilhelm Röntgen discovered the X-rays. In 1896 H. Becquerel described the phenomenon of radioactivity. He showed that a radioactive uranium salt was emitting radioactivity which passing through a metal foil darkened a photographic plate. An analogous experiment performed by S.Thomson in London was announced to the president of the Royal Society of London before the time H.Becquerel announced his discovery but Thomson never claimed priority for his discovery. Muarie Sklodowska Curie (1867-1934) was undoubtedly the most important person to attribute to the discovery of radioactivity. In 1898 she discovered radium as a natural radioactive element. This is how she describes the hard time she had, working with her husband Pierre Curie (1859-1906) for the discovery of radium and polonium: "During the first year we did not go to the theater or to a concert or visited friends. I miss my relatives, my father and my daughter that I see every morning and only for a little while. But I do not complain...". In presenting her discovery of radium, Madame Curie said: " ...in the hands of a criminal, radium is very dangerous. So we must often ask ourselves: will humanity earn or lose from this discovery? I, myself belong to those who believe the former...". The notebooks that Madame Curie had when she was working with radium and other radioactive elements like polonium, thorium and uranium are now kept in Paris. They are contaminated with radioactive materials having very long half-lives and for this reason anyone who wishes to have access to these notes should sign that he takes full responsibility. There are some more interesting points in Madame Curie's life which may not be widely known like: Although her full name is Maria Sklodowska-Curie, she is not known neither by that full name nor as Maria Sklodowska but as Marie Curie. Madame Curie was the second of five children. At the age of 24 she went to Sorbonne-Paris after being invited by her sister Bronja to study for about 2-3 years; instead she stayed in Paris for her whole life. Her doctorate was on the subject: "Research on radioactive substances" which she completed in six years under the supervision of H. Becquerel. Pierre Curie was Director of the Physics Laboratory of the Ecole Municipale of Physics and Industrial Chemistry when he married M. Curie in 1895. Pierre Curie left his other research projects and worked full time with his wife. In this laboratory M. Curie and her husband Pierre discovered radium and polonium. In 1901 Pierre Curie induced a radiation burn on his forearm by applying on his skin radiferous barium chloride for 10 hours. During World War I, M.Curie organized for the Red Cross a fleet of radiological ambulances each with X-ray apparates which were called "Little Curies". The X-ray tubes of these apparates were unshielded and so M.Curie was exposed to high doses of radiation. Once an ambulance fell into a ditch and M.Curie who was inside the ambulance was badly bruised and stayed at home for 3 days. M. Curie with her daughters, Irene and Eve, was invited and visited America in 1921. She led a successful campaign to collect radium for her experiments. Before leaving America, President Harding donated through her to the Radium Institute of Paris 1 g of radium for research purposes. At that time the process to obtain 0.5 g of pure radium bromide required 1 ton of ore and 5 tons of chemicals. No measures of radiation protection were taken back then. In 1929 Madame Curie visited the United States for a second time. She met with President Hoover and with the help of the Polish women's association in America collected funds for another gram of radium. Madame Curie died of leukemia on July 4, 1934. Sixty years after her death her remnants were laid to rest under the dome of the Pantheon. Thus she became the first woman under her own merit, to rest in the Pantheon. In 1934 at the Institute of Radiology in Paris, Frederique Joliot and Irene Curie-Joliot discovered artificial radiation. They studied alpha particles and beta;-radiation.

Editorial↗

Characterization and modeling of the metal diffusion from deep ultraviolet photoresist and silicon-based substrate.

The radioactive tracer technique was applied to investigate the out-diffusion of the transition metals (Cu, Fe and Co) from deep ultraviolet (DUV) photoresist into underlying substrate. Two important process parameters, viz., baking temperatures and substrate types (i.e., bare silicon, polysilicon, silicon oxide and silicon nitride), were evaluated. Results indicate that the out-diffusion of Co is insignificant, irrespective of the substrate type and baking temperature. The out-diffusion of Cu is significant for substrates of bare silicon and polysilicon but not for silicon oxide and nitride; for Fe, the story is reversed. The substrate type appears to strongly affect the diffusion, while the baking temperature does not. Also, the effect of solvent evaporation was found to play an important role in impurity diffusion. Using the method of numerical analysis, a diffusion profile was depicted in this work to describe the out-diffusion of metallic impurities from photoresist layer under various baking conditions. In addition, the effectiveness of various wet-cleaning recipes in removing metallic impurities such as Cu, Fe and Co was also studied using the radioactive tracer technique. Among the six cleaning solutions studied, SC2 and SPM are the most effective in impurity removal. An out-diffusion cleaning model was first proposed to describe the cleaning process. A new cleaning coefficient, h(T), was suggested to explain the cleaning effect. The cleaning model could explain the tracer results.

Journal Article↗

Zinc transport and metallothionein secretion in the intestinal human cell line Caco-2.

Caco-2, a human cell line, displays several biochemical and morphological characteristics of differentiated enterocytes. Among these is the ability to transport zinc from the apical to the basal compartment. This process was enhanced following exposure by the apical compartment to increasing concentrations of the metal. High pressure liquid chromatography fractionation of the media obtained from cells labeled with radioactive zinc showed that metallothioneins (MTs), small metal-binding, cysteine-rich proteins), were present in the apical and basal media of controls as well as in cells grown in the presence of high concentrations of zinc. Following exposure to the metal, the levels of Zn-MTs in the apical medium increased, while in the basal compartment the greatest part of zinc appeared in a free form with minor changes in the levels of basal MTs. Metabolic labeling experiments with radioactive cysteine confirmed the apical secretion of MTs. A stable transfectant clone of Caco-2 cells (CL11) was selected for its ability to express constitutively high levels of the mouse metallothionein I protein. This cell line showed an enhanced transport of the metal following exposure to high concentrations of zinc and a constitutive secretion of the mouse metallothionein I protein in the apical compartment. Together, these findings strongly support the hypothesis of a functional role between the biosynthesis and secretion of MTs and the transport of zinc in intestinal cells.

Animals↗