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The effect of zinc (Zn) injection on the stress corrosion cracking (SCC) initiation of an Alloy 182 weld metal and a 20% cold-worked (CW) type 316L stainless steel was investigated under simulated light water reactor conditions. Accelerated SCC initiation tests revealed that under both, boiling (BWR) and pressurized water reactor (PWR) conditions without Zn injection, Alloy 182 showed a higher SCC initiation susceptibility compared to the CW 316L stainless steel. With 40 ppb Zn injection, results indicate a tendency towards higher stress thresholds or lower crack densities for SCC initiation in both materials. In other words, Zn water chemistry seems to be able to mitigate SCC initiation. The optimized, Zn-treated oxide film is believed to be responsible for the improved SCC performance. However, no clear mitigation effects were observed when the specimens were pre-exposed to high-temperature water without Zn and then tested with Zn, which is likely related to the relatively short exposure time to the Zn-containing high-temperature water.

161Tb is an interesting radionuclide for application in the treatment of neuroendocrine neoplasms' small metastases and single cancer cells because of its conversion and Auger-electron emission. Tb has coordination chemistry similar to that of Lu; therefore, like 177Lu, it can stably radiolabel DOTATOC, one of the leading peptides used for the treatment of neuroendocrine neoplasms. However, 161Tb is a recently developed radionuclide that has not yet been specified for clinical use. Therefore, the aim of the current work was to characterize and specify 161Tb and to develop a protocol for the synthesis and quality control of 161Tb-DOTATOC with a fully automated process conforming to good-manufacturing-practice guidelines, in view of its clinical use. Methods:161Tb, produced by neutron irradiation of 160Gd in high-flux reactors followed by radiochemical separation from its target material, was characterized regarding its radionuclidic purity, chemical purity, endotoxin level, and radiochemical purity (RCP) in analogy to what is described in the European Pharmacopoeia for no-carrier-added 177Lu. In addition, 161Tb was introduced into a fully automated cassette-module synthesis to produce 161Tb-DOTATOC, as used for 177Lu-DOTATOC. The quality and stability of the produced radiopharmaceutical in terms of identity, RCP, and ethanol and endotoxin content were assessed by means of high-performance liquid chromatography, gas chromatography, and an endotoxin test, respectively. Results:161Tb produced under the described conditions showed, as the no-carrier-added 177Lu, a pH of 1-2, radionuclidic purity and RCP of more than 99.9%, and an endotoxin level below the permitted range (175 IU/mL), indicating its appropriate quality for clinical use. In addition, an efficient and robust procedure for the automated production and quality control of 161Tb-DOTATOC with clinically applicable specifications and activity levels, that is, 1.0-7.4 GBq in 20 mL, was developed. The radiopharmaceutical's quality control was also developed using chromatographic methods, which confirmed the product's stability (RCP ≥ 95%) over 24 h. Conclusion: The current study demonstrated that 161Tb has appropriate features for clinical use. The developed synthesis protocol guarantees high yields and safe preparation of injectable 161Tb-DOTATOC. The investigated approach could be translated to other DOTA-derivatized peptides; thus, 161Tb could be successfully applied in clinical practice for radionuclide therapy., The Journal of Nuclear Medicine, 64 (7), ISSN:0097-9058, ISSN:0022-3123, ISSN:0161-5505, ISSN:2159-662X, ISSN:1535-5667

The half-lives of 44Sc and 44mSc were measured by following their decay rate using several measurement systems: two ionization chambers and three γ-spectrometry detectors with digital and/or analogue electronics. For 44Sc, the result was the combination of seven half-life values giving a result of 4.042(7) h, which agrees with the last reported value of 4.042(3) h and confirms the near to 2% deviation from the recommended half-life of 3.97(4) h. Scandium-44 is present as an impurity in the production of 44Sc by cyclotron proton irradiation. Its half-life was determined by measurements performed a few days after End of Bomardment (EoB), so that the 44Sc decayed down to a negligible level. Seven measurements were combined to obtain an average of 58.7(3) h, which is in agreement with the recommended value of 58.6(1) h.

The half-lives of

(161)Tb has decay properties similar to those of (177)Lu but, additionally, emits a substantial number of conversion and Auger electrons. The aim of this study was to apply (161)Tb in a clinical setting and to investigate the feasibility of visualizing the physiologic and tumor biodistributions of (161)Tb-DOTATOC. Methods: (161)Tb was shipped from Paul Scherrer Institute, Villigen-PSI, Switzerland, to Zentralklinik Bad Berka, Bad Berka, Germany, where it was used for the radiolabeling of DOTATOC. In 2 separate studies, 596 and 1,300 MBq of (161)Tb-DOTATOC were administered to a 35-y-old male patient with a metastatic, well-differentiated, nonfunctional malignant paraganglioma and a 70-y-old male patient with a metastatic, functional neuroendocrine neoplasm of the pancreatic tail, respectively. Whole-body planar γ-scintigraphy images were acquired over a period of several days for dosimetry calculations. SPECT/CT images were reconstructed using a recently established protocol and visually analyzed. Patients were observed for adverse events after the application of (161)Tb-DOTATOC. Results: The radiolabeling of DOTATOC with (161)Tb was readily achieved with a high radiochemical purity suitable for patient application. Planar images and dosimetry provided the expected time-dependent biodistribution of (161)Tb-DOTATOC in the liver, kidneys, spleen, and urinary bladder. SPECT/CT images were of high quality and visualized even small metastases in bones and liver. The application of (161)Tb-DOTATOC was well tolerated, and no related adverse events were reported. Conclusion: This study demonstrated the feasibility of imaging even small metastases after the injection of relatively low activities of (161)Tb-DOTATOC using γ-scintigraphy and SPECT/CT. On the basis of this essential first step in translating (161)Tb to clinics, further efforts will be directed toward the application of (161)Tb for therapeutic purposes.

Purpose The β¯-emitting terbium-161 also emits conversion and Auger electrons, which are believed to be effective in killing single cancer cells. Terbium-161 was applied with somatostatin receptor (SSTR) agonists that localize in the cytoplasm (DOTATOC) and cellular nucleus (DOTATOC-NLS) or with a SSTR antagonist that localizes at the cell membrane (DOTA-LM3). The aim was to identify the most favorable peptide/terbium-161 combination for the treatment of neuroendocrine neoplasms (NENs). Methods The capability of the 161Tb- and 177Lu-labeled somatostatin (SST) analogues to reduce viability and survival of SSTR-positive AR42J tumor cells was investigated in vitro. The radiopeptides’ tissue distribution profiles were assessed in tumor-bearing mice. The efficacy of terbium-161 compared to lutetium-177 was investigated in therapy studies in mice using DOTATOC or DOTA-LM3, respectively. Results In vitro, [161Tb]Tb-DOTA-LM3 was 102-fold more potent than [177Lu]Lu-DOTA-LM3; however, 161Tb-labeled DOTATOC and DOTATOC-NLS were only 4- to fivefold more effective inhibiting tumor cell viability than their 177Lu-labeled counterparts. This result was confirmed in vivo and demonstrated that [161Tb]Tb-DOTA-LM3 was significantly more effective in delaying tumor growth than [177Lu]Lu-DOTA-LM3, thereby, prolonging survival of the mice. A therapeutic advantage of terbium-161 over lutetium-177 was also manifest when applied with DOTATOC. Since the nuclear localizing sequence (NLS) compromised the in vivo tissue distribution of DOTATOC-NLS, it was not used for therapy. Conclusion The use of membrane-localizing DOTA-LM3 was beneficial and profited from the short-ranged electrons emitted by terbium-161. Based on these preclinical data, [161Tb]Tb-DOTA-LM3 may outperform the clinically employed [177Lu]Lu-DOTATOC for the treatment of patients with NENs., European Journal of Nuclear Medicine and Molecular Imaging, 49 (4), ISSN:1619-7070, ISSN:1619-7089

BackgroundTerbium-155 [T1/2 = 5.32 d, Eγ = 87 keV (32%) 105 keV (25%)] is an interesting radionuclide suitable for single photon emission computed tomography (SPECT) imaging with potential application in the diagnosis of oncological disease. It shows similar decay characteristics to the clinically established indium-111 and would be a useful substitute for the diagnosis and prospective dosimetry with biomolecules that are afterwards labeled with therapeutic radiolanthanides and pseudo-radiolanthanides, such as lutetium-177 and yttrium-90. Moreover, terbium-155 could form part of the perfect “matched pair” with the therapeutic radionuclide terbium-161, making the concept of true radiotheragnostics a reality. The aim of this study was the investigation of the production of terbium-155 via the155Gd(p,n)155Tb and156Gd(p,2n)155Tb nuclear reactions and its subsequent purification, in order to obtain a final product in quantity and quality sufficient for preclinical application. The156Gd(p,2n)155Tb nuclear reaction was performed with 72 MeV protons (degraded to ~ 23 MeV), while the155Gd(p,n)155Tb reaction was degraded further to ~ 10 MeV, as well as performed at an 18 MeV medical cyclotron, to demonstrate its feasibility of production.ResultThe156Gd(p,2n)155Tb nuclear reaction demonstrated higher production yields of up to 1.7 GBq, however, lower radionuclidic purity when compared to the final product (~ 200 MBq) of the155Gd(p,n)155Tb nuclear reaction. In particular, other radioisotopes of terbium were produced as side products. The radiochemical purification of terbium-155 from the target material was developed to provide up to 1.0 GBq product in a small volume (~ 1 mL 0.05 M HCl), suitable for radiolabeling purposes. The high chemical purity of terbium-155 was proven by radiolabeling experiments at molar activities up to 100 MBq/nmol. SPECT/CT experiments were performed in tumor-bearing mice using [155Tb]Tb-DOTATOC.ConclusionThis study demonstrated two possible production routes for high activities of terbium-155 using a cyclotron, indicating that the radionuclide is more accessible than the exclusive mass-separated method previously demonstrated. The developed radiochemical purification of terbium-155 from the target material yielded [155Tb]TbCl3in high chemical purity. As a result, initial cell uptake investigations, as well as SPECT/CT in vivo studies with [155Tb]Tb-DOTATOC, were successfully performed, indicating that the chemical separation produced a product with suitable quality for preclinical studies.

The βThe capability of theIn vitro, [The use of membrane-localizing DOTA-LM3 was beneficial and profited from the short-ranged electrons emitted by terbium-161. Based on these preclinical data, [

The decay of terbium-161 results in the emission of β¯-particles as well as conversion and Auger electrons, which makes terbium-161 interesting for therapeutic purposes. The aim of this study was to use dual-isotope SPECT imaging in order to demonstrate visually that terbium-161 and lutetium-177 are interchangeable without compromising the pharmacokinetic profile of the radiopharmaceutical. The 161Tb- and 177Lu-labeled somatostatin (SST) analogues DOTATOC (agonist) and DOTA-LM3 (antagonist) were tested in vitro to demonstrate equal properties regarding distribution coefficients and cell uptake into SST receptor-positive AR42J tumor cells. The radiopeptides were further investigated in AR42J tumor-bearing nude mice using the method of dual-isotope (terbium-161/lutetium-177) SPECT/CT imaging to enable the visualization of their distribution profiles in the same animal. Equal pharmacokinetic profiles were demonstrated for either of the two peptides, irrespective of whether it was labeled with terbium-161 or lutetium-177. Moreover, the visualization of the sub-organ distribution confirmed similar behavior of 161Tb- and 177Lu-labeled SST analogues. The data were verified in quantitative biodistribution studies using either type of peptide labeled with terbium-161 or lutetium-177. While the radionuclide did not have an impact on the organ distribution, this study confirmed previous data of a considerably higher tumor uptake of radiolabeled DOTA-LM3 as compared to the radiolabeled DOTATOC.

A family of three picolinate pyclen-based ligands, previously investigated for the complexation of Y3+ and some lanthanide ions (Gd3+, Eu3+), was studied with 161Tb and 177Lu in view of potential radiotherapeutic applications. The set of six Tb3+ and Lu3+ complexes was synthesized and fully characterized. The coordination properties in the solid state and in solution were thoroughly studied. Potentiometric titrations, supported by density functional theory (DFT) calculations, showed the very high stability constants of the Tb3+ and Lu3+ complexes, associated with remarkable kinetic inertness for up to 30 days in 1 M HCl. A complete radiolabeling study performed with both 161Tb and 177Lu radionuclides, including experiments with regard to the stability with and without scavengers and kinetic inertness using challenging agents, proved that the ligands could reasonably compete with the DOTA analogue. To conclude, the potential of using the same ligand for both radiotherapy and optical imaging was highlighted for the first time.

A family of three picolinate pyclen based ligands, previously investigated for the complexation of Y3+ and some lanthanide ions (Gd3+, Eu3+), was studied with 161Tb and 177Lu in view of potential radiotherapeutic applications. The set of six Tb3+ and Lu3+ complexes was synthesized and fully characterized. The coordination properties in the solid state and in solution were thoroughly studied. Potentiometric titrations, corroborated by DFT calculations, showed the very high stability constants of the Tb3+ and Lu3+ complexes, which are associated to remarkable kinetic inertness. A complete radiolabeling study performed with both 161Tb and 177Lu radionuclides, including experiments with regard to the stability with and without scavengers and kinetic inertness using challenging agents, proved that the ligands could reasonably compete with the DOTA analogue. To conclude, the potential of using the same ligand for both radiotherapy and optical imaging was highlighted for the first time.

Radionuclide production and development has a long history at the Paul Scherrer Institute (PSI) and dates back to the founding times of its forerunner institutions: the Federal Institute for Reactor Research and the Swiss Institute for Nuclear Research. The facilities used for this purpose have evolved substantially over the last five decades. Many radiometals in use today, as radiopharmaceuticals, are for the diagnosis and treatment of disease, with the most popular means of detection being Positron Emission Tomography. These positron emitters are easily produced at low proton energies using medical cyclotrons, however, developments at these facilities are lacking. Currently, the fixed 72 MeV proton beam at PSI is degraded at IP2 irradiation station to provide the desired energy to irradiate targets to produce the likes of 44Sc, 43Sc and 64Cu as a proof of principle, which are of great interest to the nuclear medicine community. This development work can then be implemented at facilities containing medical cyclotrons. A history of the development of radionuclides at PSI, along with current development and projects with partner institutions, is described., Chimia, 74 (12), ISSN:0009-4293

Pt particles, injected into the feed water of boiling water reactors, are used to mitigate stress corrosion cracking in austenitic stainless steels of the primary water cooling circuit, but the mechanism behind this mitigation process is still not well understood. This feasibility study was performed, in order to get first insights and understanding on the deposition mechanism of the Pt particles, their shape and spatial distribution, with respect to stainless steel oxide crystals and their composition. The Pt particles and oxide crystals were characterized by electron microscopy, namely scanning electron microscopy, high-resolution transmission electron microscopy, and scanning transmission electron microscopy coupled to energy dispersive X-ray spectrometry. It appears that the surface of the stainless steel is covered by polyhedral crystals, which consist of oxide of mainly Fe, mixed with Ni and Cr. Fe is rather homogeneously distributed within the crystals, while Ni concentrates in their centre relative to the Cr that segregates towards their surface. The Pt particles, with an average diameter of 14 nm, stick to the oxide crystal's surfaces and are rather evenly distributed without preference to oxide composition. The particles are consisting of pure metallic Pt with a round to facetted or rhombohedral morphology.

With the aim of mitigating stress corrosion cracking (SCC) in reactor internals and recirculation pipes, the boiling water reactor plant Leibstadt (KKL) changed in 2008 from normal water chemistry ...

Stress corrosion cracking (SCC) is a well-known degradation mechanism for components of boiling water reactors (BWRs). Therefore the mitigation of SCC is important for ensuring the integrity of the reactor system. Noble metal chemical application (NMCA) has been developed by General Electric to mitigate SCC and reduce the negative side-effects of hydrogen water chemistry used initially for SCC mitigation. NMCA is now widely applied as an online process (OLNC) during power operation. However, the understanding of the parameters that control the formation and deposition of the noble metal (Pt) particles in a BWR was still incomplete. To fill this knowledge gap, systematic studies on the formation and deposition behaviour of Pt particles in simulated and real BWR environment were performed in the framework of a research project at PSI. The present paper summarizes the most important findings. Experiments in a sophisticated high-temperature water loop revealed that the flow conditions, water chemistry, the Pt injection rate, and the pre-conditioning of the stainless steel surfaces have an impact on the Pt deposition behaviour. Slower Pt injection rates and stoichiometric excess of H2 over O2 produce smaller particles, which may increase the efficiency of the OLNC technique in mitigating SCC. Surfaces with a well-developed oxide layer retain more Pt particles. Furthermore, the pre- and post-OLNC exposure times play an important role for the Pt deposition on specimens exposed at the KKL power plant. Redistribution of Pt in the plant takes place, but most of the Pt apparently does not redeposit on the steel surfaces in the reactor system. Comparison of lab and plant results also demonstrated that plant OLNC applications can be simulated reasonably well on the lab scale.

The radiolanthanide

Noble metals are added to boiling water reactors (BWRs) to mitigate stress corrosion cracking of structural components made from steels and Ni-based alloys and this technology is referred to as Noble Metal Chemical Addition (NMCA) or NobleChemTM. There is a growing concern that NMCA can cause unwanted harmful effects on the corrosion and hydrogen uptake properties of Zircaloy-2 fuel cladding. To investigate this, we have subjected Zircaloy-2 fuel claddings to out-of-pile BWR conditions in a custom-built autoclave. These claddings are oxidized in pressurized hot water (280 °C, 9 MPa) for 25, 60 and 150 days, wherein Pt nanoparticles (~10 nm) were simultaneously injected. Cross-sectional focused ion beam cuts made at the oxide-metal interface reveal that the oxide growth is not significantly influenced by the local Pt loadings (≤ 1 µg·cm-2). Surprisingly, an inverse correlation was observed between oxide thicknesses and metal's hydrogen contents. Interestingly, Pt catalysts have led to diminished hydrogen absorption in specimens with liner exposed to the hot water. Overall, Pt catalysts exhibited no detrimental effects on the corrosion rate and hydrogen absorption in Zircaloy-2.

A well-known issue in boiling water reactors (BWR), which can threaten their structural integrity, is stress corrosion cracking (SCC) of reactor internals and recirculation pipes due to the accumulation of oxidizing radiolysis products of water. Currently, many operators of BWRs use combined platinum particle and hydrogen injection into the reactor water to mitigate SCC by lowering the electrochemical corrosion potential. It is essential for efficient mitigation that Pt particles reach all water-wetted surfaces, including crevices and cracks, which are also reached by the oxidizing species. In this study, a set of crevices with different widths and orientations with respect to the fluid flow are investigated using numerical simulation tools and compared against experimental findings. The Reynolds-Averaged Navier–Stokes models are used to compute the mean turbulent flow quantities in three-dimensional crevices, and the discrete random walk model is used to evaluate the effect of velocity fluctuations on particle movement. The Lagrangian particle tracking analysis is performed and the average concentration of deposited particles on the surface of crevices is evaluated and compared with experimental results. The results show that Reynolds stress model combined with enhanced wall treatment provides a more accurate prediction of particle concentration and distribution on the surface of crevices than SST k–ω turbulence model, which was expected, owing to the anisotropic nature of the Reynolds stress model. Furthermore, analyses on the particle deposition shows that three different mechanisms play important roles in enhancing deposition on the surface of crevice, that is, flow penetration, interception and turbulent eddy entrainment.

Tellurium (Te) and bismuth (Bi) are two metal(loid)s often enriched together with gold (Au) in hydrothermal deposits; however the speciation and transport properties for these two metals in hydrothermal systems are poorly understood. We investigated the effect of chloride on the speciation of Te(IV) and Bi(III) in hydrothermal solutions using in-situ XAS spectroscopy. At ambient temperature, oxy-hydroxide complexes containing the [TeO 3 ] moiety (e.g., H 3 TeO 3 + under highly acidic conditions) predominate in salty solutions over a wide range in pH and salt concentrations. Te(IV)–Cl complexes only appear at pH 25 °C ≤ 2 and high Cl − activity (≥ 10). The highest order Te(IV) chloride complex detected is TeCl 4(aq) , and contains the [TeCl 4 ] moiety. Upon heating to 199 °C, the Te(IV)–Cl complexes become more stable; however they still required highly acidic conditions which are likely to exist only in very limited environments in nature. At ambient temperature, Bi(III) is coordinated to 5.5(5) Cl atoms in high salinity, acidic (HCl ≥ 0.5 m) chloride solutions. This, combined with large EXAFS-derived structural disorder parameters, suggests that the Bi(III) complex is most likely present as both BiCl 5 2 − and BiCl 6 3 − . The number of Cl atoms coordinated to Bi(III) decreases with increasing temperature; at around 200 °C and above, Bi(III) is coordinated to three Cl atoms. Overall the data show that Te(IV) chloride complexes can be ignored in predicting Te mobility under oxidizing conditions in most geological environments, but that Bi(III) chloride complexes are expected to account for Bi mobility in acidic brines. New thermodynamic properties for Bi(III) chloride complexes are provided to improve reactive transport modeling of Bi up to 500 °C. Although higher order complexes such as BiCl 5 2 − and BiCl 6 3 − exist at ambient temperature, the BiCl 3 (aq) complex becomes the predominant chloride complex in saline solutions at T ≥ 200 °C.

The radiolanthanide 161Tb is being studied as an alternative to 177Lu for targeted radionuclide tumor therapy. Both β--particle emitters show similar chemical behavior and decay characteristics, but 161Tb delivers additional conversion and Auger electron emissions that may enhance the therapeutic efficacy. In this study, the half-life of 161Tb was determined by a combination of three independent measurement systems: reference ionization chamber (CIR, chambre d'ionization de reference), portable ionization chamber (TCIR) and a CeBr3 γ-emission detector with digital electronics. The half-life determined for 161Tb is 6.953(2) days, showing a significant improvement in the uncertainty, which is one order of magnitude lower, with a deviation of 0.91% from the last nuclear data reference value. The previous large uncertainty of the half-life had a direct impact on activity measurements. Now it is no more an obstacle to a primary standardization.

Stress corrosion cracking of stainless steel components in boiling water reactors can threaten their structural integrity and lead to costly maintenance operations. A low electrochemical corrosion potential can reduce the susceptibility of stainless steel to stress corrosion cracking. Injecting hydrogen into the reactor feed water lowers the ECP. The efficiency of hydrogen injection is improved in presence of catalytically active noble metals. Therefore, platinum (Pt) compounds are added to the reactor feed water and then deposit on the water-wetted surfaces. To understand the parameters affecting the application and mitigation processes, stainless steel coupons in as-received or pre-oxidized conditions were exposed in a high-temperature water loop to simulated boiling water reactor water conditions with the addition of platinum. Coupons were placed at three locations: in an autoclave with quasi-stagnant flow conditions (few mm/s), in a specimen holder with a flow velocity of 0.10 m/s, and in another with...

Noble metal injection is widely used to mitigate stress corrosion cracking (SCC) of reactor components. Despite its wide use, there are still open questions regarding the parameters affecting the application process and possible improvements to it. Laboratory experiments in a high-temperature water loop at PSI were complemented by exposure of specimens in the mitigation monitoring system (MMS) at KKL. The influence of parameters such as flow conditions, structural material composition, surface roughness and geometry on the deposition behavior of the platinum (Pt) nanoparticles was investigated. Furthermore, the long-term stability of the coverage of surfaces by Pt particles was analyzed. The composition of the underlying alloy was found to have an effect on the deposition behavior, whereas surface roughness has no measurable impact. Pt showed a limited durability on steel surfaces and, after the end of the application, the remobilized Pt seems to re-deposit only minimally on nearby surfaces.

The speciation of Mn(II) in acidic brines under a wide range of conditions (30–550 °C, 600 bar, 0.100–10.344 m chloride and 0.110–2.125 m bromide) was investigated using in situ X-ray Absorption Spectroscopy (XAS). Increasing temperature and/or salinity results in a structural change of the Mn(II) complexes from octahedral to (distorted) tetrahedral. Octahedral species predominate at room temperature within the whole salinity range and persist up to ∼400 °C in low salinity solutions (mCl 3 m, Cl:Mn ratio > 53) is MnCl3(H2O)−, and that a lower order chlorocomplex, MnCl2(H2O)2(aq), is the predominant species in low salinity solutions (mCl

Despite the close association between tellurium (Te) and gold (Au) in many epithermal, orogenic, and intrusion-related hydrothermal ore deposits, the hydrothermal chemistry of Te remains poorly understood. We studied the protonation/ deprotonation and structure of tellurous acid ((H2TeO3)-O-IV) species in aqueous solutions and in water vapor as a function of pH from room-temperature to 505 degrees C using a number of methods: TeO2(s) solubility in solution and steam, potentiometry, NMR spectroscopy, and in situ XAS spectroscopy. The solubility of TeO2(s) increases by up to a factor 80 between ambient temperature and 200 degrees C. As the temperature increases, the pH range over which the neutral species H2TeO3(aq) dominates to the detriment of the ionic species H3TeO3+, HTeO3-and TeO32-expands. The structure of these species is a trigonal pyramid with the Te atom at its apex, indicating a stereochemically active electron pair. The Te-O bond lengths increase with increasing protonation (i.e., decreasing pH). Although hydrated tellurite species such as TeO2(H2O)(g) and TeO2(H2O)(2)(g) exist in significant concentrations in vapors equilibrated with TeO2(s), these species are unlikely to play a significant role in natural systems, because of the high solubility of Te(IV) in the liquid phase under these conditions. Solubility calculations conducted with the new and existing properties confirm the importance of reduced species for the vapor transport of Te, with a partitioning coefficient (Kd = Te concentration in vapor/Te concentration in liquid) up to >10(5) in favor of the vapor, and ppm concentrations of Te in reduced vapors at 300 degrees C. Thermodynamic calculations show that slightly basic, mildly reduced fluids that can transport Au efficiently as Au(HS)(2)(-) can also carry significant Te (e.g., similar to 100 ppb at 300 degrees C). The calculations also suggest that under magmatic hydrothermal conditions, large amounts of Te can be transported as Te(IV) complexes in oxidized fluids (coexisting with SO2(g)). Reduction of Te(IV) caused by processes such as fluid-rock interaction or fluid mixing will lead to a dramatic decrease in the solubilities of both Te and Au, and to the precipitation of telluride minerals. (C) 2013 Elsevier Ltd. All rights reserved.

The solubility of bismuth oxide (α-Bi 2 O 3(s) ; bismite) in near-neutral sodium perchlorate solutions at 65 and 80 °C, and pure water from 150 to 600 °C, P Sat to 800 bar was studied using various batch-reactor techniques and in situ XAS spectroscopy. The solubility of Bi 2 O 3(s) follows a similar trend to Sb 2 O 3(s) (senarmontite), which has been interpreted in terms of a neutral Sb(OH) 3(aq) complex. Thus a similar neutral complex, Bi(OH) 3(aq) , is inferred for Bi. XANES spectroscopy confirms that the Bi(OH) 3(aq) complex carries a stereochemically active lone electron pair, and EXAFS data suggest that the geometry of the complex changes little over the temperature range 380–610 °C at 800 bar, with three oxygen neighbors at ∼2.08 A. The solubility data obtained in this study are used in conjunction with thermodynamic properties for α-Bi 2 O 3(s) to obtain thermodynamic parameters for Bi(OH) 3(aq) within the framework of the revised Helgeson–Kirkham–Flowers (HKF) equation of state. Speciation calculations using these new properties indicate that, similarly to arsenic and antimony, bismuth is transported predominantly as a neutral hydroxide complex in a wide range of temperature, pressure, and fluid compositions. In contrast to arsenic and antimony, bismuth is much less soluble in typical hydrothermal fluids in the form of hydroxide complexes, and high temperatures (⩾400 °C) are required for significant Bi transport by aqueous fluids. These results are consistent with the common association between Bi mineralization and magmatism.

Mineralization at Maldon, Victorian goldfields, Australia, is part of the Western Lachlan Foldbelt and is hosted by deformed Lower Ordovician metasediments intruded by the Late Devonian Harcourt Granite. Gold–Bi–Te–S associations in the deposit include four gold-bearing minerals (maldonite, native gold, jonassonite, and aurostibite) and a range of sulphotellurides from the tetradymite group, all of which are paragenetically tied to native bismuth. The simpler phase associations, involving bismuth, maldonite and one or the other Bi-(sulpho)tellurides, resemble the equivalents of eutectics in the system Au–Bi–Te and hint at crystallisation from melts. The complex associations include symplectites of gold and bismuth resulting from replacement of maldonite and are dominated by co-existing, sulphur-bearing species (joseite-A, joseite-B, an unnamed phase with bulk composition approximating to Bi 3 (Te,S) 2 and jonassonite). The complexity of such assemblages is also underpinned by chemical–structural inhomogeneity within the unnamed phase, i.e. nanoscale domains of Bi 14 (Te,S) 9 and Bi 5 (Te,S) 3 , as documented from electron diffractions obtained from a FIB-TEM foil. Although such lattice-scale intergrowths reveal polysomatic disorder that can be associated with replacement of one telluride by another, the structural modules in the overall stacking sequence indicate formation under local equilibrium conditions. The mineralogical complexity of all Au–Bi–Te–S associations can be modelled in terms of interaction between simpler assemblages and sulphur-bearing fluids. Three stages—all involving gold minerals—are recognised: (1) bismuth + maldonite ± hedleyite; (2) Bi-sulphotellurides + jonassonite, and decomposition of maldonite (gold + bismuth); and (3) bismuthinite + gold from decomposition of maldonite or jonassonite. The last stage is coincident with chloritisation and occurs during or following granite emplacement. Thermodynamic modelling of maldonite replacement by bismuthinite and gold indicates conditions to overlap with the pyrite–hematite buffer at 258 °C if neutral fluids are involved. The general replacement model for the deposit shows that local-scale reworking of maldonite and resultant gold remobilisation contributed to the apparent abundance of native gold. This interpretation is consistent with the protracted geological history at Maldon where granite intrusion post-dates an orogenic event. Initial sulphur-poor assemblages crystallised from melts predating granite emplacement. The latest sulphidation event is attributed to retrograde fluids in the contact aureole, whereas the earlier one could also have been produced during the multi-stage deformation. Although observed assemblages and textures are the product of a complex sequence of overprinting, there is no need to invoke input of gold from more than a single fluid generation.

The transformation of calaverite to gold under hydrothermal conditions was studied experimentally by probing the effects of temperature (140 to 220 °C), pH (2–12), oxidant concentration, geometric specific surface area, and solid-weight to fluid-volume ratio on the sample textures and the reaction kinetics. Under all of the experimental conditions explored, calaverite transformed to various extents to metallic gold. The replacement is pseudomorphic, as gold preserves the external dimensions of calaverite. The resulting elemental gold is porous; consisting of filament-shaped aggregates with diameters ranging from 200 to 500 nm and lengths up to 25 μm. Gold crystals appear to be randomly oriented with respect to the twinned calaverite grains. The transformation proceeds via a coupled calaverite dissolution–gold precipitation mechanism, with calaverite dissolution being rate-limiting relative to gold precipitation. Tellurium is lost to the bulk solution as Te(IV) complexes, and may further precipitate away from the dissolution site (e.g., autoclave walls) as TeO2(s). In contrast, gold precipitates locally near the calaverite dissolution site. Such local gold precipitation is facilitated by fast heterogeneous nucleation onto the calaverite surface. The dissolution of calaverite and the overall reaction are oxidation reactions, and oxygen diffusion through the porous metallic gold layer probably plays an important role in sustaining the reaction. A similar dissolution-reprecipitation process may be responsible for the formation of mustard gold during the weathering of gold-telluride ores. At 220 °C, solid-state replacement of calaverite by gold is slow (months), but calaverite grains ~100 μm in size are fully replaced in

We used µ-XANES spectroscopy to measure the oxidation state of europium in-situ at near-µm resolution in hydrothermal scheelite from the giant Archean gold deposits of Kalgoorlie, Western Australia. By combining these measurements with µ-XRF imaging, it is possible to distinguish inhomogeneities in Eu2+/Eu3+ ratios that developed during mineral precipitation from the effects of subsequent hydrothermal alteration and weathering. Thermodynamic analysis reveals that under the conditions typical of the formation of many Au deposits, the Eu2+/Eu3+ ratio in the hydrothermal fluid is highly sensitive to pH. The range in pH calculated from the Eu2+/Eu3+ ratios in the analyzed scheelite corresponds to a maximum in Au solubility under the ore-forming conditions, and suggests buffering of pH by the CO2(aq)-rich fluid. The primary heterogeneity of the Karlgoorlie scheelite most likely results from pH oscillating between fluid- and rock-buffered conditions, and reflects the dynamics of the hydrothermal system.

The ruthenium(II) hexaaqua complex [Ru(H2O)6]2+ reacts with dihydrogen under pressure to give the h2-dihydrogen ruthenium(II) pentaaqua complex [Ru(H2)(H2O)5]2+.The complex was characterized by 1H, 2H and 17O NMR: d H = -7.65 ppm, J HD = 31.2 Hz, d O = -80.4 ppm (trans to H2) and d O = -177.4 ppm (cis to H2).The H-H distance in coordinated dihydrogen was estd. to 0.889 .ANG. from J HD, which is close to the value obtained from DFT calcns. (0.940 .ANG.). Kinetic studies were performed by 1H and 2H NMR as well as by UV-Vis spectroscopy, yielding the complex formation rate and equil. consts.: k f = (1.7 +- 0.2) * 10-3 kg mol-1 s-1 and K eq = 4.0 +- 0.5 mol kg-1.The complex formation rate with dihydrogen is close to values reported for other ligands and thus it is assumed that the reaction with dihydrogen follows the same mechanisn (I d).In deuterated water, one can observe that [Ru(H2)(H2O)5]2+ catalyzes the hydrogen exchange between the solvent and the dissolved dihydrogen.A hydride is proposed as the intermediate for this exchange.Using isotope labeling, the rate const. for the hydrogen exchange on the h2-dihydrogen ligand was detd. as k 1 = (0.24 +- 0.04) * 10-3 s-1.The upper and lower limits of the pK a of the coordinated dihydrogen ligand have been estd.:3 < pK a < 14.

The complex formation in water between the stable tricarbonyltriaqua fac-[(CO)(3)Re(H(2)O)(3)](+) (1) complex and N- and S-donor ligands has been studied by high-pressure (1)H NMR. Rate and equilibrium constants for the formation of [(CO)(3)Re(Pyz)(H(2)O)(2)](+), [(CO)(3)(H(2)O)(2)Re(mu-Pyz)Re(H(2)O)(2)(CO)(3)](2+), [(CO)(3)Re(THT)(H(2)O)(2)](+), and [(CO)(3)Re(DMS)(n)()(H(2)O)(3-n)](+) (n = 1-3) (Pyz = pyrazine, THT = tetrahydrothiophene, DMS = dimethyl sulfide) have been determined and are in accord with previous results (Salignac, B.; Grundler, P. V.; Cayemittes, S.; Frey, U.; Scopelliti, R.; Merbach, A. E.; Hedinger, R.; Hegetschweiler, K.; Alberto, R.; Prinz, U.; Raabe, G.; Kolle, U.; Hall, S. Inorg. Chem. 2003, 42, 3516). The calculated interchange rate constant k(1)' (Eigen-Wilkins mechanism) increases from the hard O- and N-donors to the soft S-donors, as exemplified by the following series: TFA (trifluoroacetate) (k(1)' = 2.9 x 10(-3) s(-1)) < Br(-) < CH(3)CN < Pyz < THT < DMS < TU (thiourea) (k(1)' = 41.5 x 10(-3) s(-1)). On the other hand, values remain close to that of water exchange k(ex) on 1 (k(ex) = 6.3 x 10(-3) s(-1)). Thus, an I(d) mechanism was assigned, suggesting however the possibility of a slight deviation toward an associatively activated mechanism with the S-donor ligands. Activation volumes determined by high-pressure NMR, for Pyz as Delta V(++)(f,1) = +5.4 +/- 1.5, Delta V(++)(r,1) = +7.9 +/- 1.2 cm(3) mol(-)(1), for THT as Delta V(++)(f,1) = -6.6 +/- 1, Delta V(++)(r,1) = -6.2 +/- 1 cm(3) mol(-1), and for DMS as Delta V(++)(f,1) = -12 +/- 1, Delta V(++)(r,1) = -10 +/- 2 cm(3) mol(-1) revealed the ambivalent character of 1 toward water substitution. Hence, these findings are interpreted as a gradual changeover of the reaction mechanism from a dissociatively activated one (I(d)), with the hard O- and N-donor ligands, to an associatively activated one (I(a)), with the soft S-donor ligands.

International audience; The structure of Bi(III) clusters in aqueous concentrated acidic perchlorate solutions has been studied by means of X-ray absorption spectroscopy (XAS). The XAS data show that the polynuclear [Bi6O4(OH)4]6+ complex with a cage structure predominates at room temperature in acidic Bi-rich solutions. This complex breaks down to form mononuclear complexes with increasing temperature to 428 K. This behavior is consistent with theoretical predictions based on considerations of the electrostatic repulsion, which increases sharply as the dielectric constant of the solvent decreases with increasing temperature.

Since the first facile synthesis of [Ru(H2O)(6)](tos)(2) was published at the beginning of the eighties, several Ru-II aqueous inorganic and organometallic complexes were described, showing the increasing interest in this kind of compound due to potential applications in catalysis and medicine. To understand what governs the reactivity of the ligands in the first coordination sphere of the Ru-II center. we discuss its solution behavior, starting with the simplest aqueous species [Ru(H2O)(6)](2-) and moving progressively in complexity with selected examples. In addition, we present variable-pressure measurements with two objectives to determine activation volumes for mechanistic assignments. and to shift equilibria by increasing the solubility of gaseous molecules.

We report a new method for pre-treatment of refractory gold-bearing tellurides employing the hydrothermal mineral replacement reactions. The method is illustrated by the replacement of calaverite by metallic gold at 150–250 °C under vapor saturated pressures. The influences of temperature, pH, and additional salts (NaCl and Na2SO4) on the conversion rate were investigated using the orthogonal array design method. The results indicate that temperature is the most significant factor, followed by pH, and then additional salts. The optimal condition for fast and low cost conversion is 200 °C, pH 6.0, 0.01 M NaCl, and

International audience; Although the crustal abundance of tellurium (Te) is about half of that of gold (Au), several classes of Au deposits are highly enriched in Te. Our understanding of the nature of this Au-Te association is hampered by the lack of experimental studies of Te geochemistry at elevated temperature. We characterized the structure of polytelluride solutions from room temperature to 599 °C at 800 bar using in situ X-ray absorption spectroscopy. Both ab-initio XANES and EXAFS fits show that polytellurides are stable up to the highest temperature, with planar structures (four- or threefold coordination of Te) giving way to linear chains (e.g., Te22− ion) at temperatures above ~200 °C. This is the first experimental confirmation of the thermal stability of polytelluride species. The data show that polytellurides play an important role in Te transport in reduced S-rich or CO2-rich solutions and vapors.

International audience; Xocolatlite, Ca2Mn4+2Te6+2O12*H2O, is a rare new mineral from the Moctezuma deposit in Sonora, Mexico. It occurs as chocolate-brown crystalline crusts on a quartz matrix. Xocolatlite has a copper-brown streak, vitreous luster, and is transparent. Individual crystals show a micaceous habit. Refractive indices were found to be higher than 2.0. Density calculated from the empirical formula is 4.97 g/cm3, and immersion in Clerici solution indicated a density higher than 4.1 g/cm 3. The mineral is named after the word used by the Aztecs for chocolate, in reference to its brown color and provenance. The crystallographic characteristics of this monoclinic mineral are space group P2, P2/m, or Pm, with the following unit-cell parameters refined from synchrotron X-ray powder diffraction data: a= 10.757(3) Å, b = 4.928(3) Å, c = 8.942(2) Å, β = 102.39(3)°, V = 463.0(3) Å3, and Z = 2. The unavailability of a suitable crystal prevented single-crystal X-ray studies. The strongest 10 lines of the X-ray powder diffraction pattern are [d in Å (I) (hkl)]: 3.267(100)(012), 2.52(71)(303), 4.361(51)(002), 1.762(39)(323), 4.924 (34)(010), 2.244(32)(313), 1.455(24)(006), 1.996(21)(014), 1.565(20)(611), and 2.353(18)(411). XANES Te LIII-edge spectra of a selection of Te minerals (including xocolatlite) and inorganic compounds showed that the position of the absorption edge can be reliably related to the oxidation state of Te. XANES demonstrated that xocolatlite contains Te6+ as a tellurate group. Water has been tentatively included in the formula based on IR spectroscopy that indicated the presence of a small amount of water. Raman, IR, XANES, and X-ray diffraction data together with the chemical composition show a similarity of xocolatlite to kuranakhite. A possible series may exist between these two species, xocolatlite being the Ca-rich end-member and kuranakhite the Pb-rich one.

The water exchange process on fac-[(CO)3Mn(H2O)3]+ and fac-[(CO)3Tc(H2O)3]+ was kinetically investigated by 17O NMR as a function of the acidity, temperature, and pressure. Up to pH 6.3 and 4.4, respectively, the exchange rate is not affected by the acidity, thus demonstrating that the contribution of the monohydroxo species fac-[(CO)3M(OH)(H2O)2] is not significant, which correlates well with a higher pKa for these complexes compared to the homologue fac-[(CO)3Re(H2O)3]+ complex. The water exchange rate K298ex/s(-1) (DeltaHex double dagger/kJ mol(-1); DeltaSex double dagger/J mol(-1) K(-1); DeltaV double dagger/cm3 mol-1) decreases down group 7 from Mn to Tc and Re: 23 (72.5; +24.4; +7.1) > 0.49 (78.3; +11.7; +3.8) > 5.4 x 10(-3) (90.3; +14.5; -). For the Mn complex only, an O exchange on the carbonyl ligand could be measured (K338co = 4.3 x 10(-6) s(-1)), which is several orders of magnitude slower than the water exchange. In the case of the Tc complex, the coupling between 17O (I = 5/2) and 99Tc (I = 9/2) nuclear spins has been observed (1J99Tc,17O = 80 +/- 5 Hz). The substitution of water in fac-[(CO)3M(H2O)3]+ by dimethyl sulfide (DMS) is slightly faster than that by CH3CN: 3 times faster for Mn, 1.5 times faster for Tc, and 1.2 times faster for Re. The pressure dependence behavior is different for Mn and Re. For Mn, the change in volume to reach the transition state is always clearly positive (water exchange, CH3CN, DMS), indicating an Id mechanism. In the case of Re, an Id/Ia changeover is assigned on the basis of reaction profiles with a strong volume maximum for pyrazine and a minimum for DMS as the entering ligand.

The pH-dependent water-exchange rates of [(CO)2(NO)Re(H2O(cis))2(H2O(trans))]2+ (1) in aqueous media were investigated by means of 17O NMR spectroscopy at 298 K. Because of the low pK(a) value found for 1 (pK(a) = 1.4 +/- 0.3), the water-exchange rate constant k(obs)(H2O(trans/cis)) was analyzed with a two-pathway model in which k(Re)(H2O(trans/cis)) and k(ReOH)(H2O)(trans/cis)) denote the water-exchange rate constants in trans or cis position to the nitrosyl ligand on 1 and on the monohydroxo species [(CO)2(NO)Re(H2O)2(OH)]+ (2), respectively. Whereas the rate constants k(ReOH)(H2O)(trans)) and k(ReOH)(H2O)(cis)) were determined as (4.2 +/- 2) x 10(-3) s(-1) and (5.8 +/- 2) x 10(-4) s(-1), respectively, k(Re)(H2O)(trans)) and k(Re)(H2O)(cis)) were too small to be determined in the presence of the much more reactive species 2. Apart from the water exchange, an unexpectedly fast C identical with 16O --C identical withO exchange was also observed via NMR and IR spectroscopy. It was found to proceed through 1 and 2, with rate constants k(Re)(CO) and k(ReOH)(CO) of (19 +/- 4) x 10(-3) s(-1) and (4 +/- 3) x 10(-3) s(-1), respectively. On the other hand, N identical with 16O --N identical with *O exchange was not observed.

The water exchange process on [(CO)(3)Re(H(2)O)(3)](+) (1) was kinetically investigated by (17)O NMR. The acidity dependence of the observed rate constant k(obs) was analyzed with a two pathways model in which k(ex) (k(ex)(298) = (6.3 +/- 0.1) x 10(-3) s(-1)) and k(OH) (k(OH)(298)= 27 +/- 1 s(-1)) denote the water exchange rate constants on 1 and on the monohydroxo species [(CO)(3)Re(I)(H(2)O)(2)(OH)], respectively. The kinetic contribution of the basic form was proved to be significant only at [H(+)] < 3 x 10(-3) M. Above this limiting [H(+)] concentration, kinetic investigations can be unambiguously conducted on the triaqua cation (1). The variable temperature study has led to the determination of the activation parameters Delta H(++)(ex) = 90 +/- 3 kJ mol(-1), Delta S(++)(ex) = +14 +/- 10 J K(-1) mol(-1), the latter being indicative of a dissociative activation mode for the water exchange process. To support this assumption, water substitution reaction on 1 has been followed by (17)O/(1)H/(13)C/(19)F NMR with ligands of various nucleophilicities (TFA, Br(-), CH(3)CN, Hbipy(+), Hphen(+), DMS, TU). With unidentate ligands, except Br(-), the mono-, bi-, and tricomplexes were formed by water substitution. With bidentate ligands, bipy and phen, the chelate complexes [(CO)(3)Re(H(2)O)(bipy)]CF(3)SO(3) (2) and [(CO)(3)Re(H(2)O)(phen)](NO(3))(0.5)(CF(3)SO(3))(0.5).H(2)O (3) were isolated and X-ray characterized. For each ligand, the calculated interchange rate constants k'(i) (2.9 x 10(-3) (TFA) < k'(I) < 41.5 x 10(-3) (TU) s(-1)) were found in the same order as the water exchange rate constant k(ex), the S-donor ligands being slightly more reactive. This result is indicative of I(d) mechanism for water exchange and complex formation, since larger variations of k'(i) are expected for an associatively activated mechanism.

Thiosulfate and ammonia mixtures may be more environmentally benign alternatives to cyanide for leaching Au from ores. In this method, the Cu(I)/Cu(II) couple acts as a redox mediator aiding in the oxidative dissolution of metallic Au. Information about the speciation of Cu(I) and Cu(II) in these lixiviant solutions is paramount to the optimization of gold ore processing conditions. With this in mind, we have carried out XANES, EXAFS and UV-Vis spectroscopic studies of the speciation of Cu(I) in mixed thiosulfate-chloride and ammonia-chloride solutions. In thiosulfate-chloride solutions, the EXAFS studies indicate that the geometry of the predominant Cu(I) complex is distorted trigonal (triangular planar), with an average of 2 sulfur atoms + 1 oxygen atom occupying the coordination sphere. This indicates that the stability of the [Cu(S2O3)3]5− complex is lower than previously proposed. Formation constants for Cu(I) thiosulfate complexes have been derived on the basis of systematic UV-Vis measurements of solutions with varying [S2O3]/[Cl] ratios. Only one mixed chloride-thiosulfate complex, [Cu(H2O)(S2O3)Cl]2−, was found to predominate over the range of conditions investigated. For Cu(I) in ammonia-chloride solutions, our results confirm the broad stability of [Cu(NH3)2]+ and we have also identified a stable mixed amminechlorocopper(I) complex, [CuCl(NH3)]+. XAS reveals that these two complexes share a linear geometry. This study demonstrates that combinations of methods are required to decipher the geometry and thermodynamic properties of transition metal complexes in mixed ligand chemical systems where many species may coexist. Our results allow more comprehensive predictions of solution speciation and contribute to efforts to design improved methods to process gold ore with thiosulfate and ammonia lixiviants.

Tellurium is the only element which forms a variety of minerals with gold as principal component (e.g. calaverite AuTe2, krennerite (AuAg)Te2, petzite Ag3AuTe2 and sylvanite AgAuTe4). These minerals have been known for a long time and are of economic value in many deposits such as Cripple Creek (Colorado), Emperor (Fiji), and Sacarimb (Romania), and “orogenic” gold deposits, including the giant Golden Mile deposit (Western Australia). However, knowledge the formation of these minerals is still incomplete.