A multi-scalar study of the long-term reactivity of uranium mill tailings from Bellezane site (France).

The mill tailings from uranium mines constitute very low-level, long-lived, radioactive process waste. Their long-term management therefore requires a good understanding of the geochemical mechanisms regulating the mobility of residual uranium and radium-226. This article presents the results of the detailed characterization of the tailings resulting from the dynamic leaching processes used on the ore of the La Crouzille mining division and stored at the Bellezane site (Haute-Vienne, France) for over 25 years. A multi-scalar and multidisciplinary approach was developed based on a study of the site's history, on the chemical, radiological and mineralogical characterizations of the solid fraction of the tailings, and on porewater analyses. These were complemented by thermodynamic equilibrium models to predict the long-term mobility of U and 226Ra. Weakly acidic (pH = 6.35) and oxidizing (Eh = 138 mV/SHE) porewaters had a sulfated-magnesian facies ([SO4]tot = 43 mmol/L; [Mg]tot = 33 mmol/L) with an accessory calcium bicarbonate component (TIC = 25 mmol/L; [Ca]tot = 13 mmol/L) and dissolved concentrations of uranium and 226Ra of 12 × 10-6 mol/L and 0.58 Bq/L respectively. Ultra-filtration at 10 kDa indicated the absence of colloidal phases. The characterization of the tailings confirmed their homogeneity from a radiological, chemical and mineralogical point of view. The residual U and 226Ra concentrations measured in the solid were 160 ppm and 25 Bq/g respectively, in accordance with the initial ore grades and mill yields, or more than 99% of the total stock. In terms of chemical and mineralogical composition, the tailings were mainly composed of minerals from the granitic ore (quartz, potassium feldspar, plagioclases and micas) in association with their weathering products (smectite and ferric oxyhydroxides) and with neo-formed minerals following rapid diagenesis after neutralization of the tailings before their emplacement (gypsum and barite). All these minerals are effective traps for the retention of U and 226Ra. The uranium is distributed partly in micrometer scale uraninite and coffinite refractory phases embedded in grains of quartz, and partly sorbed to smectite and ferric oxyhydroxides. The 226Ra on the other hand is trapped mainly within the barite. The aqueous concentrations of U and 226Ra could be described using a thermodynamic approach so that their long-term mobility can subsequently be assessed by modeling. The paragenesis of the tailings could be seen to be stable over time with the exception of neo-formed gypsum and calcite, which will gradually dissolve. The presence of retention traps offering surplus capacity, i.e. smectite, ferric oxyhydroxides and barite, will maintain the U and the 226Ra at very low aqueous concentrations, even under oxidizing conditions. Moreover, the low permeability of the mill tailings leads, in the case of 226Ra, to behavior dictated only by the radioactive decay.

Kinetic study of hydrogen lateral diffusion at high temperature in a directly-bonded InP-SiO2/Si substrate.

Hybrid integration of III-V materials onto silicon by direct bonding technique is a mature and promising approaches to develop advanced photonic integrated devices into the silicon photonics platform. In this approach, the III-V material stack is grown on an InP wafer in a unique epitaxial step prior to the direct bonding process onto the silicon-on-insulator wafer. Currently, no additional epitaxial regrowth steps are implemented after bonding. This can be seen as a huge limitation as compared to the III-V on III-V wafer mature technology where multi-regrowth steps are most often implemented. In this work, we have studied the material behavior of an InP membrane on silicon (InPoSi) under epitaxial regrowth conditions by metal-organic vapor phase epitaxy (MOVPE). MOVPE requires high-temperature elevation, typically above 600 °C. We show for the first time the appearance of voids at 400 °C in an InP seed (100 nm) directly-bonded onto a thermally oxidized Si substrate despite the use of a thick SiO2 oxide (200 nm) at the bonding interface. This phenomenon is explained by a weakening of the bonding interface while high-pressurized hydrogen is present. A kinetic study of the hydrogen lateral diffusion is carried out, enabling the assessment of its lateral diffusion length. To overcome the void formation, highly efficient outgassing trenches after bonding are demonstrated. Finally, high-quality AlGaInAs-based multi-quantum well (MQW) heterostructure surrounded by two InP layers was grown by MOVPE on InPoSi template patterned with outgassing trenches. This process is not only compatible with MOVPE regrowth conditions (650 °C under PH3) but also with conventional fabrication processes used for photonic devices.

[Membranous lipodystrophy caused by chemotherapy]. / Lipodystrophie membraneuse secondaire à une chimiothérapie.

INTRODUCTION: Membranous lipodystrophy represents a peculiar dermatopathologic type of cystic forming adipose tissue necrosis. In skin pathology two distinct entities are currently known: a primary idiopathic type and a secondary type found in association with various cutaneous or systemic diseases (lupus erythematosus, scleroderma, dermatomyositis, venous disorders, trauma, diabetes mellitus...). This secondary type is more common. CASE REPORT: We report the case of a female patient treated with cytostatic regimen for metastatic adenocarcinoma of the breast. She was seen with cyclic painful attacks of hypodermitis of lower limbs following drug infusions. Attacks finally vanished after treatment withdrawal. Membranous lipodystrophy was observed microscopically. DISCUSSION: This is, to the best of our knowledge, the first case of membranous lipodystrophy occurring during cytostatic treatment. The origin of such a phenomenon remains nuclear but cystic formation occurs after adipocyte necrosis and membranes are thought to be formed from dead cells plasma membrane remnants. Primary cell injury could be due to ischemia to which adipose tissue is especially susceptible. In our case, role of circulatory troubles or cytostatic chemotherapy could be equally discussed. However cyclic attack of painful hypodermatitis following drug administration was strongly in favour of treatment responsibility. Moreover clearing of lesions after treatment discontinuation brought more arguments for this last hypothesis.

[Cutaneous osteoma and Albright's hereditary osteodystrophy]. / Ostéomes cutanés et ostéodystrophie héréditaire d'Albright.

Albright's hereditary osteodystrophy has been diagnosed in a 35-year-old woman who presented recurrent cutaneous ossifications of the auricular area. The patient exhibited other cutaneous ossifications, a short stature with obesity, round face, stocky hands and feet, radiological calcifications of the skull and of the hands, cataract, auditive impairment and dental abnormalities. Serum calcium, phosphorus and parathyroid hormone levels were normal. Urine excretion of phosphorus and cyclic adenosine monophosphate (cAMP) markedly increased after intravenous injection of parathyroid hormone, referring to pseudopseudohypoparathyroidism. Albright's hereditary osteodystrophy is associated either with pseudohypoparathyroidism type 1a characterized by parathyroid hormone and other hormones resistance or with pseudopseudohypoparathyroidism without hormone resistance. This two conditions are considered variants of the same defect of the stimulatory G protein of adenylate cyclase which is necessary for the action of parathyroid hormone, and other hormones to use cAMP as an intracellular second messenger. But Albright's hereditary osteodystrophy may be associated with other biochemical abnormalities, such as defect of catalytic activity of adenylate cyclase in pseudohypoparathyroidism type 1c. There is an important variability of the clinical, biochemical and genetical expression of pseudohypoparathyroidism and today classification is provisional.