Behaviour of advanced tritium breeder pebbles under simultaneous action of accelerated electrons and high temperature

The authors greatly acknowledge the technical and experimen-tal support of O. Valtenbergs and L. Avotina (Institute of Chemical Physics, University of Latvia). The work is performed in the frames of the University of Latvia financed project No. Y9-B044-ZF-N-300, “Nano, Quantum Technologies, and Innovative Materials for Eco-nomics”.Advanced lithium orthosilicate (Li4SiO4) pebbles with additions of lithium metatitanate (Li2TiO3) as a secondary phase are suggested as a potential source for tritium breeding in future nuclear fusion reactors. The advanced Li4SiO4 pebbles with different contents of Li2TiO3 were examined before and after simultaneous action of 5 MeV accelerated electron beam (dose rate: up to 10 MGy h−1) and high temperature (up to 1120 K) in a dry argon atmosphere. The accumulated radiation-induced defects (RD) and radiolysis products (RP) were studied by electron spin resonance (ESR) spectrometry and thermally stimulated luminescence (TSL) technique. The phase transitions were studied with powder X-ray diffraction (p-XRD). The microstructure and mechanical strength of the pebbles, before and after irradiation, were investigated by scanning electron microscopy (SEM) and comprehensive crush load tests. The obtained results revealed that the irradiation temperature has a significant impact on the accumulation of RD and RP in the advanced Li4SiO4 pebbles, and with an increasing content of Li2TiO3, the concentration of accumulated paramagnetic RD and RP decreases. Major changes in the mechanical strength, microstructure and phase composition of the advanced pebbles were not detected after irradiation.University of Latvia Y9-B044-ZF-N-300; Institute of Solid State Physics, University of Latvia as the Center of Excellence has received funding from the European Union’s Horizon 2020 Framework Programme H2020-WIDESPREAD-01-2016-2017-TeamingPhase2 under grant agreement No. 739508, project CAMART

Reinvestigación de los ocres de antimonio históricos de cervantitas-tipo

Antimony ocher are yellowish antimony oxo-hydroxides formed by weathering of stibnite (Sb2S3). They occur naturally as single crystallized phases in the isometric system with pyrochlore type structure, containing some Ca and water molecules in the structure, its range in composition can be expressed by the formula: Sb5+ 2-x (Sb3+, Ca)y (O, OH, H2O)6-7, in which y is generally near 1, and x ranges from 0 to 1. Furthermore, Sb-ochres use to include substitutional As, Fe, Ta, Ti, Cu and others. This chemical variability keeping the structure has generated historical confusion of names of equivalent minerals with similar X-ray diffraction patterns being necessary the use of additional techniques. The mineral-type Cervantite from Cervantes (Spain) (Ca, Sb3+)2(Sb5+)2O6(OH) was disapproved at 1954 and re-approved at 1962 as α-Cervantite Sb3+Sb5+O4 analyzing synthetic and natural antimony ochres from other localities, e.g., Brasina (Serbia) by X-ray diffraction. We herein characterize both historical specimens-type from Cervantes (Lugo, Spain) and Zajaca-Stolice (Brasina, Serbia) from the chemical-elemental, structural, thermal and speciation points of view, together with a vibrational study by Raman and FTIR, since the X-ray diffraction patterns of isometric samples with pyrochlore-type structure are excessively similar among them. The Cervantes specimen-type could be named hydroxycalcioromeite (Ca, Sb3+)2(Sb5+)2O6(OH) whereas the Brasina specimen-type Ca2(Sb5+)4O12(OH)2 is very similar but lacking Sb3+; both specimens contain Ca and hydrous components, faraway of the official anhydrous orthorhombic α-Cervantite (Sb3+Sb5+O4) setting. Micro-Raman was essential determining molecular phases and Sb-O bond vibrations, FTIR and DTA-TG finding hydroxyl groups and XPS defining Sb speciation.Los ocres de antimonio son óxi-hidróxidos formados por meteorización de estibnita (Sb2S3). Normalmente aparecen como fases minerales simples cristalizadas en el sistema cúbico con estructura de tipo pirocloro y conteniendo algo de calcio y moléculas de agua en su red cristalina. Sus rangos composicionales pueden ser expresados por la fórmula: Sb5+ 2-x (Sb3+, Ca)y (O, OH, H2O)6-7, donde (y) está cerca de 1 y (x) va de 0 a 1. También es muy frecuente que los ocres de antimonio incluyan sustituciones de As, Fe, Ta, Ti, Cu y otros. Esta variabilidad química dentro de la misma estructura ha generado confusiones históricas de nombres de minerales equivalentes con patrones de difracción de rayos X muy similares siendo importante complementar con técnicas analíticas adicionales. El mineral-tipo cervantita de Cervantes (Lugo, España) (Ca, Sb3+)2(Sb5+)2O6(OH) fue desacreditado en 1954 y re-aprobado en 1962 como α-cervantita Sb3+Sb5+O4 difractando muestras de óxidos de antimonio sintéticos y naturales de otras localidades, como por ejemplo de Brasina (Serbia). En este trabajo estudiamos ambos minerales-tipo de Cervantes (Lugo, Spain) y de Zajaca-Stolice (Brasina, Serbia) desde los puntos de vista estructural, químico-elemental, termal, vibracional y de especiación química, asumiendo que los patrones de difracción de rayos X, los de la estructura tipo pirocloro son muy similares entre ellos. El espécimen tipo de Cervantes (Lugo) puede ser considerado como hydroxycalcioromeita (Ca,Sb3+)2(Sb5+)2O6(OH) mientras que el de Brasina Ca2(Sb5+)4O12(OH)2 es muy similar pero sin Sb3+. Ambas muestras contienen calcio y componentes hidratados, es decir, ambos están lejos de ser la α-Cervantita (Sb3+Sb5+O4) oficial anhidra y ortorrómbica. La espectroscopia micro-Raman es esencial para determinar fases minerales y vibraciones de enlaces Sb-O, mientras que espectroscopia FTIR y los ATD-TG fueron útiles para determinar grupos hidroxilos y aguas moleculares y la espectroscopia XPS para definir las especiaciones químicas del antimonio

Aplicación de la termoluminiscencia de aluminosilicatos alcalinos a la dosimetria ambiental retrospectiva

Este trabajo ha sido posible gracias a la financiación de: La UE a través del proyecto 'Dose Reconstructiorl (FI4P-CT 95-0011d). El CSN con el proyecto 'Dosimetría Retrospectiva (DOSEl (acuerdo• CIEMAT-CSN 96/208). Y La DGICYT con el proyecto 'Implicaciones de la luminiscencia espectral de feldespatos alcalinos en alteración de granito, dosimetría ambiental y datación geológica' (PB 95-0108)Peer Reviewe

Thermo- and cathodoluminescence properties of lepidolite

Lepidolite, K(Li,Al)3(Si,Al)4O10(F,OH)2, and many of the related phyllosilicate mineral of the mica group have been well studied from the chemical and structural point of view; however, to the best of our knowledge, studies on their luminescence properties have been scarcely reported. This work focuses on the thermoluminescence (TL) and cathodoluminescence (CL) response of a natural lepidolite from Portugal previously characterized by means of environmental scanning electron microscope (ESEM) and X-ray fluorescence (XRF) and atomic absorption spectroscopy (AAS) techniques. The complexity of the thermoluminescence glow curves of non-irradiated and 1Gy irradiated samples suggests a structure of a continuous trap distribution involving multiorder kinetics. UV-IR CL spectral emission shows seven peaks centered at 330, 397, 441, 489, 563, 700 and 769 nm. Such emission bands could be due to (i) structural defects, i. e. [AlO4] or non-bridging oxygen hole centers, and (ii) the presence of point defects associated with Mn2+ and Fe3+.Peer Reviewe

Characterization of natural and induced UV-blue thermoluminescence properties of kaolinite

The UV-blue thermoluminescence (TL) emission of natural kaolinite has been investigated to determine its potential use in the field of dating and retrospective dosimetry. This paper focuses on: (i) The dose dependence of the 400nm TL intensity of kaolinite that exhibits an excellent linearity in the range of 50mGy-8Gy. (ii) The stability of the induced TL signal after six months of storage, shows an initial rapid decay (ca. 45%) maintaining the stability from 40 days onwards which indicates that the electron population decreases asymptotically by the X-axis and the involved electrons are located in deeper traps at room temperature. The fading process can be fitted to a first order decay equation of the sort y=y0+A exp (-x/t). (iii) The tests of thermal stability at different temperatures allow us to speculate in a continuous trap distribution with progressive changes in the glow curve shape, intensity and temperature position of the maximum peak. According to this behaviour some physical parameters have been estimated.Peer Reviewe

Radioluminescence and thermoluminescence emission spectra of a leucite of Monte Somma (Italy)

[ES] La leucita natural (KAlSi2O6), materia prima para la fabricación de cerámicas dentales, es un material potencialmente válido para su utilización con fines dosimétricos ya que su respuesta luminiscente (radioluminiscencia -RL- y termoluminiscencia -TL-) en la región espectral del visible (200-800nm) es similar a la de otros aluminosilicatos utilizados también con fines dosimétricos. A pesar de la complejidad de las curvas, los espectros de emisión de TL y RL obtenidos con una leucita del Monte Somma (Nápoles, Italia) se pueden ajustar a un número máximo de seis funciones gaussianas situadas a 300, 380, 430, 480, 550 y 680 nm con significado físico. Este ajuste indica que en ambos procesos las trampas electrónicas que intervienen tienen el mismo origen. El análisis químico realizado por Fluorescencia de Rayos X (FRX) de la leucita estudiada permite intentar vincular el contenido de impurezas presentes en la red cristalina del material con las bandas de emisión que se producen como consecuencia de las distorsiones estructurales que se generan en la red cristalográfica formada por los tetraedros de SiO4 y [AlO4].[EN] Natural leucite (KAlSi2O6), one of the main components of dental ceramics, shows similar radioluminescence (RL) and thermoluminescence (TL) response than other aluminosilicates (in the 200-800nm region) employed for dosimetric purposes. Despite the complex structure of the emission spectra, both glow curves can be fitted to six gaussian functions peaked at 300, 380, 430, 480, 550 and 680nm. We infer that the involved electronic traps are of the same origin regardless of the luminescence process. The chemical analysis performed by X-ray fluorescence (XRF) allows us to seek relationships between the content of the impurities of the crystal lattice and the emission bands.Este trabajo ha sido financiado por la CICYT (proyecto BFM2002-00048). Los espectros de TL y RL se realizaron en la Univ. de Sussex (UK) con la ayuda del Prof. P.D. Townsend.Peer reviewe

Improvements to x-ray diffractometers: Heaters, hygrometry, and thermodifferential and spectra analyses

3 pages, 2 figures, 1 table.We describe a newly designed stainless steel door which holds cooling fluids and permits the connection of a set of self-improvements to mechanical supplies, sensors, thermocouples, electronic circuits, and new software to traditional x-ray diffraction chambers. Some compatible analytical routines, at various gas temperatures (from 18 to 200 °C), stem from restricted combinations of stimulation sources to the sample (x irradiation and heating) and the detector sensors (Geiger x-ray diffraction spectra charge coupled devices, humidity, image TV, thermocouples differential thermal analysis installed). Phase transitions of solids can be detected by spectral, structural, geometrical, and thermodifferential methods.The Spanish DGICYT PB98-0501 and European PNICYDT 1FD97-0959-C03-01 projects supported the work.Peer reviewe

Luminescence characterization of a sodium-rich feldspar

We, herein, report on the radioluminescence and thermoluminescence properties of a sodium-rich feldspar ((Na,K)[AlSi3O8]) with a mean molecular composition of orthoclase (Or) and Albite (Ab) of Or1Ab99. Despite the complexity of the luminescence emissions of the sample, it is possible to determine six different emission bands at about 300, 380, 420, 460, 550 and 680 nm. The 300 nm emission can be associated to structural defects related to the recombination process in which the diffusion of Na ions is involved. The UV-blue emission bands have the following features: (i) the 380 nm, typical of mineral phases containing SiO4 groups, is related to intrinsic defects in the lattice; (ii) the 420 nm band is associated with the presence of Cu(II) ions close to the hole traps or the recombination on a centre formed from a hole-oxygen atom adjacent to two Aluminum atoms (Al-O-Al) and (iii) the 460 nm waveband is due to the presence of Ti4+. The green and red emissions are, respectively, associated with the presence of Mn2+ and Fe3+ ions. The ratio between the relative intensities, peaked at 290 (the more intense waveband) and 550 nm is about 10 for both TL and RL, which implies that the efficiency of recombination centres does not change regardless of the type of the process.We are grateful to Prof. Dr. P.D. Townsend for the analyses in the high sensitivity spectrometer of Sussex (UK). This work has been supported by the C.I.C.Y.T. CGL2004-03564/BTE and Comunidad Autonoma de Madrid (CAM) MATERNAS (S-0505/MAT/0094) projects. Thanks are also given to Paul Giblin for the critical review of the manuscriptPeer Reviewe

Characterization of the cathodoluminescence emission of kamphaugite-(Y) and kristiansenite from Spain

This paper reports on the cathodoluminescence (CL) emission of kamphaugite-(Y) (CaY(CO)(OH)·HO) and kristiansenite [CaScSn(SiO)(SiOOH)] that display very complex spectra. The carbonate sample, growing in spheres no longer than 3 mm, contains significant concentrations of REE giving rise to sharp and narrow wavebands peaked at 312, 486, 546, 574 and 626 nm. These wavebands would be, respectively, associated with the presence of Gd (P → S transition), Dy (F → H), Tb (D → F), Dy (F → H) and Sm (G → H). Kristiansenite, appearing as an isolated pseudo-hexagonal pyramidal crystal smaller than 600 µm, hardly has lanthanide elements and the CL emission is composed of broad wavebands peaked at 298 nm (linked to defect-sites caused by the presence of the Na-0.49%), 334 (due to oxygen vacancies and Me–O bonding defects), 422 (–O–O– type defects and/or O intrinsic defects), 494 (self-trapped excitons), 578 [Mn giving rise to T(G) → A(S) transition and/or Ti/Sn redox reactions] and 654 nm [due to FeT(G) → A(S) transitions].This work has been partially supported by the CIEMAT-266-DORES