Granitic groundwater colloids sampling and characterisation: the strategy for artefact elimination

Colloids were separated by submicro-filtration of granitic groundwater samples collected at-line under in-situ thermodynamic conditions after down-hole groundwater sampling and transfer at the well head. The methodology avoids the generation of artefacts produced by pH changes due to CO2 exchange, yielding potential carbonate precipitation, or by O2 contamination yielding oxidized insoluble phases. The enhanced pressure and the anoxic conditions are also maintained through the filtering procedure. This procedure was carried out after a period of regular sampling of groundwater pumped to the ground surface and continuous on-line long-term measurements (weeks, months) of chemical and physical parameters in the unbroken sample water both at the ground surface and at depth down-hole. Colloid samples were characterized on the submicro-filtration membrane by scanning electron microscopy. Under deep granite groundwater conditions, natural colloids occur sparsely. The colloid concentration was determined C col ∼1 and ∼50μg L−1 for sizes ranging from 50 to 200nm or n col ∼ 3.9 × 109 and 47 × 109 L−1 for sizes larger than 50nm for KFM11A, Forsmark, and KLX17A, Laxemar, Oskarshamn, respectively, Sweden. These colloids are expected to be clay particles with an average size smaller than 200nm for the Na-Ca-Cl and Na-Cl groundwaters (pH 7.6 and 8.00, ionic strength ∼10−1 and ∼10−2 mol L−1, respectively, for KFM11A and KLX17A), the colloid concentrations were comparable with values previously reported in the literatur

Micro-focussed XAFS spectroscopy to study Ni-bearing precipitates in the metal of corroded Zircaloy-2

The present work concerns an investigation of the local atomic environment of Ni-containing secondary phase precipitates (SPP) present in the metal-part of Zircaloy-2 cladding tubes. An unirradiated Zircaloy-2 and two specimens irradiated in a commercial nuclear power plant are characterized using μ-focussed synchrotron radiation, and by x-ray absorption fine structure (XAFS) spectroscopy. The patterns of Ni K-edge XANES and EXAFS of SPP in unirradiated and irradiated cladding are found different. Considering the fact that Ni-bearing SPP in the unirradiated samples are mainly Zintl phase Zr2(Fe, Ni) type, a detailed EXAFS analysis of near-neighbor Ni atoms has been made. The result of a curve fit for the first two shells shows that about 2 Ni(Fe) and 8Zr atoms are coordinated at2.68 and 2.77Å, respectively, around a central Ni atom in the SPP. XANES data analysis provides total electronic density of states at the Fermi level of unirradiated Zr2(Fe, Ni). At the Ni K-edge EXAFS spectra of irradiated SPP, however, only a single scattering peak is observed demonstrating the structural disorder introduced by the neutron irradiation. The coordination number of the Ni neighboring shells is reduced markedly due to the formation of point and extended defects in the damaged SPP lattice. Dissolution of Ni from the SPP is also evident from the data. The results of this study provide a further basis for the description of both crystallographic and electronic structures of intermetallic second-phase precipitates found in Zr-based alloy

Simulating uranium sorption onto inorganic particles:The effect of redox potential

An analytical expression is proposed to simulate the effects of pH and redox potential (E) on the sorption of uranium onto model inorganic particles in aquatic environments instead of following an experimental approach providing a list of empirical sorption data. The expression provides a distribution coefficient (Kd) as function of pH, E and ligand concentration (complex formation) applying a surface complexation model on one type of surface sites (>SuOH). The formulation makes use of the complexation and hydrolysis constants for all species in solution and those sorbed at the surface, using correlations between hydrolysis constants and surface complexation constants, for the specific sorption sites. The model was applied for the sorption of uranium onto aluminol, iron hydroxide and silanol sites, mimicking respectively ‘clean’ clay or ‘dirty’ clay and ‘clean’ sand or ‘dirty’ sand (‘dirty’ referring to iron hydroxide contaminated), in absence or presence of carbonates in solution. The calculated distribution coefficients are very sensitive with the presence or absence of carbonates. The Kd values obtained by applying the model are compared with values reported in the literature for the sorption of uranium onto specific adsorbents. It is known that in surface water, U(VI) and its hydroxides are the primary stable species usually observed. However, reduction to U(IV) is possible and may be simulated during sorption or when the redox potential (E) decreases. Similar simulations are also applicable to study the sorption of other redox sensitive elements

ODS steel as structral material for high temperature nuclear reactors

Oxide dispersed strengthened (ODS) ferritic-martensitic steels are investigated as possible structural material for the future generation of High Temperature Gas Cooled Nuclear Reactors. The Ni based austenitic ODS superalloys are not considered, because of the Ni presence, which is unfavorable under neutron irradiation. ODS-steels are considered to replace other high temperature materials for tubing or structural parts. Interestingly, ODS is also considered as material being used in future fusion applications. The oxide particles serve for interfacial pinning of moving dislocations. Therefore the creep resistance is improved. In case of the usage of these materials in reactor, the behavior under irradiation must be further clarified. In this paper the effects induced by He implantation are investigated. The induced swelling is measured and the mechanical behavior of the irradiated surface is investigated. These first tests are performed at room temperature, where a clear swelling and hardening could be observed.Окисно дисперговані зміцнені (ОДЗ) феритно-мартенситні сталі досліджуються як можливі конструкційні матеріали для нового покоління високотемпературних ядерних реакторів з газовим охолодженням. Аустенітні ОДЗ-сплави на основі никелю не вивчаються завдяки никелю, присутність якого під дією опромінення небажана. ОДЗ-сталі разглядаються як можливі кандидати на заміну інших високотемпературних матеріалів для вигoтовлення трубопроводів або інших конструкційних вузлів. Цікаво, що ОДЗ-матеріали розглядаються також з точки зору їх можливого використання для майбутнього застосування в термоядерних пристроях. Окисні частки служать як міжфазні пастки для закріплення дислокацій, що рухаються. У разі використання ціх материалів в реакторі їх поведінка під опроміненням повинна вивчатись більш ретельно. В роботі досліджуються ефекти, зумовлені проникненням Не. Вимірюється зумовлене розпухання та механічні характеристики опроміненої поверхні. Ці перші дослідження були виконані при кімнатній температурі, коли можно чітко спостерігати розпухання та зміцнення.Окисно диспергированные упрочненные (ОДУ) ферритно-мартенситные стали изучались как возможные конструкционные материалы для нового поколения высокотемпературных ядерных реакторов с газовым охлаждением. Аустенитные ОДУ-суперсплавы на базе никеля не рассматривались из-за присутствия никеля, который нежелателен при нейтронном облучении. ОДУ-стали рассматривались как возможные заменители других высокотемпературных материалов для изготовления трубопроводов или других композиционных узлов. Интересно, что ОДУ рассматривается так же, как возможный кандидат для использования в термоядерных устройствах. Окисные частицы служат как межфазные ловушки для закрепления движущихся дислокаций. Поэтому сопротивление ползучести увеличивается. В случае использования этих материалов в реакторе их поведение под облучением должно изучаться более тщательно. В предлагаемой работе исследуются эффекты, обусловленные внедрением Не. Измеряется обусловленное распухание и механические характеристики облученной поверхности. Эти первые испытания были выполнены при комнатной температуре, когда можно явно наблюдать распухание и упрочнение

Considerations for Prenatal Counselling of Patients with Cardiac Rhabdomyomas based on their Cardiac and Neurologic Outcomes

Cardiac rhabdomyomas are benign cardiac tumours with few cardiac complications, but with a known association to tuberous sclerosis that affects the neurologic outcome of the patients. We have analysed the long-term cardiac and neurological outcomes of patients with cardiac rhabdomyomas in order to allow comprehensive prenatal counselling, basing our findings on the records of all patients seen prenatally and postnatally with an echocardiographic diagnosis of cardiac rhabdomyoma encountered from August, 1982, to September, 2007. We analysed factors such as the number and the location of the tumours to establish their association with a diagnosis of tuberous sclerosis, predicting the cardiac and neurologic outcomes for the patients. Cardiac complications include arrhythmias, obstruction of the ventricular outflow tracts, and secondary cardiogenic shock. Arrhythmias were encountered most often during the neonatal period, with supraventricular tachycardia being the commonest rhythm disturbance identified. No specific dimension or location of the cardiac rhabdomyomas predicted the disturbances of rhythm. The importance of the diagnosis of tuberous sclerosis is exemplified by the neurodevelopmental complications, with four-fifths of the patients showing epilepsy, and two-thirds having delayed development. The presence of multiple cardiac tumours suggested a higher risk of being affected by tuberous sclerosis. The tumours generally regress after birth, and cardiac-related problems are rare after the perinatal period. Tuberous sclerosis and the associated neurodevelopmental complications dominate the clinical picture, and should form an important aspect of the prenatal counselling of parent

A Positron Emission Tomography Study of Voluntarily and Electrically Contracted Human Quadriceps

peer reviewe

Adsorption behavior of Eu(III) on partially Fe(III)- or Ti(IV)-coated silica

The adsorption behavior of Eu(III) onto silica surface, which was partially coated with Fe(III) or Ti(IV), was investigated to determine Fe(III) or Ti(IV) effects on the surface reaction of lanthanides on mineral surfaces in groundwater. Compared with a parallel uncoated silica, the Fe(III)-coated silica did not enhance the adsorption of Eu(III). However, enhanced adsorption of Eu(III) on the Ti(IV)-coated silica was observed by increasing the amount of Ti(IV) on the silica surface