Features of the in-situ experiments on studying of tritium release from lithium ceramic Li2TiO3 using vacuum extraction method
Abstract The paper presents the results of reactor experiments with lithium ceramic Li2TiO3 performed at the WWR-K research reactor (Almaty, Kazakhstan). A qualitative analysis of the experimental results is presented. The following general results are obtained from the experiments performed by the vacuum extraction method: • Almost no tritium is released in the form of tritium water vapor, and the processes associated with tritium interaction with water vapor can be excluded from the consideration; • a significant amount of tritium is released as T2 molecule; • in long-term irradiation, a significant growth of tritium release in the form of T2 molecule with the time of irradiation is obser…
Spectrometric analysis of inner divertor materials of JET carbon and ITER-like walls
Abstract One of main reasons of the Joint European torus (JET) transformation from the carbon (JET-C) to ITER-like (JET-ILW) wall was high tritium retention of carbon. In order to compare the tritium retention, samples of analogous positions of the plasma-facing side of vertical tiles No. 3 of two campaigns: JET-C (2008–2009) and JET-ILW (2011–2012) were cut out. Temperature-programmed tritium desorption spectrometry in He + 0.1% H2 gas flow showed that JET-C sample without a tungsten coating had by a factor of >20 higher surface concentration of tritium than JET-ILW tungsten-coated sample: 4.9 × 1013 and 1.7–2.2 × 1012 T atoms/cm2 respectively. Installation of metallic plasma facing wall i…
Effective Degradation of Cigarette Butts via Treatment with Old Landfill Leachates
In this paper, results of feasibility study on microplastics (MPs) assessment in leachates from the Latvian solid municipal landfill Getliņi are discussed. The application of leachates for the treatment of cigarette butts (CGB) was evaluated. Methods of fluorescent microscopy, Fourier transform infrared (FTIR) spectroscopy and FTIR-microscopy were used for the identification and characterization of MPs in the leachates and analysis of CGB. Presence of the secondary MPs (e.g., degraded polyolefin mixtures) was determined in the tested landfill leachates, while cellulose acetate (CA) was not determined in these products. The leachates were tested as potential media for the thermophilic (55°C)…
Irradiation of nuclear materials with laser-plasma filaments produced in air and deuterium by terrawatt (TW) laser pulses
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”.
Radiation resistance of nanolayered silicon nitride capacitors
Abstract Single-layered and multi-layered 20–60 nm thick silicon nitride (Si3N4) dielectric nanofilms were fabricated using a low-pressure chemical vapour deposition (LPCVD) method. The X-ray photoelectron spectroscopy (XPS) confirmed less oxygen content in the multi-layered nanofilms. The capacitors with Si3N4 multilayer demonstrated a tendency to a higher breakdown voltage compared to the capacitors with Si3N4 single layer. Si3N4 nanofilms and capacitors with Si3N4 dielectric were exposed to 1 kGy dose of gamma photons. Fourier transform infrared (FTIR) spectroscopy analysis showed that no modifications of the chemical bonds of Si3N4 were present after irradiation. Also, gamma irradiation…
Study of tritium and helium generation and release from lead-lithium eutectics Li15.7Pb under neutron irradiation
Abstract This paper describes the experiments on study of tritium and helium generation and release processes from lead-lithium eutectics Li15.7Pb. The irradiation was performed at the IVG.1M research reactor at 6 MW of thermal power. The irradiation temperature increased step by step from 225 to 550 °C. A qualitative assessment of the experimental results showed that as the temperature rises above 390 °C, the tritium flux from the sample consisting of T2 and HT molecules decreases. It was concluded that the observed effect is similar to the previously observed one for lead-lithium eutectics with Li17Pb83 composition.
Radiation stability of long-term annealed bi-phasic advanced ceramic breeder pebbles
Abstract Advanced ceramic breeder pebbles consisting of Li4SiO4 and additions of Li2TiO3 were tested regarding their long-term thermal and to their radiation stability. As-prepared and long-term annealed pebbles were irradiated with accelerated electrons (up to 6 MGy) to investigate the formation of radiation-induced defects and radiolysis products caused by ionizing radiation. By using Raman spectroscopy the formation of significant amounts of radiolysis products can be excluded. Electron spin resonance spectrometry revealed several paramagnetic radiation-induced defects, such as HC2 centres ( SiO 4 3 - and TiO 3 - ), E’ centres ( SiO 3 3 - and TiO 3 3 - ), Ti 3 + centres and peroxide radi…
Formation and accumulation of radiation-induced defects and radiolysis products in modified lithium orthosilicate pebbles with additions of titanium dioxide
Abstract Lithium orthosilicate (Li4SiO4) pebbles with 2.5 wt.% excess of silicon dioxide (SiO2) are the European Union's designated reference tritium breeding ceramics for the Helium Cooled Pebble Bed (HCPB) Test Blanket Module (TBM). However, the latest irradiation experiments showed that the reference Li4SiO4 pebbles may crack and form fragments under operation conditions as expected in the HCPB TBM. Therefore, it has been suggested to change the chemical composition of the reference Li4SiO4 pebbles and to add titanium dioxide (TiO2), to obtain lithium metatitanate (Li2TiO3) as a second phase. The aim of this research was to investigate the formation and accumulation of radiation-induced …
Structural changes and distribution of accumulated tritium in the carbon based JET tiles
Abstract In this study the tritium distribution and the effect of structural changes thereon have been analyzed in the bulk of the tile selected from the JET Mark II SRP divertor. Tritium content has been analyzed by the full combustion technique [1] . The structure has been investigated by the method of Scanning Electron Microscopy. Tritium depth profiles have been measured at different poloidal positions. A high specific activity of tritium (up to 156 MBq g −1 ) was found at the plasma-facing surface. At some tile positions up to 98–99% of the T can be in the surface slice of 1 mm thickness, whereas in other poloidal positions there can be more T in the bulk than at the surface. The struc…
Novel method for determination of tritium depth profiles in metallic samples
Tritium accumulation in fusion reactor materials is considered a serious radiological issue, therefore a lot of effort has been concentrated on the development of radiometric techniques. A novel method, based on gradual dissolution, for the determination of the total tritium content and its depth profiles in metallic samples is demonstrated. This method allows for the measurement of tritium in metallic samples after their exposure to a hydrogen and tritium mixture, tritium containing plasma or after irradiation with neutrons resulting in tritium formation. In this method, successive layers of metal are removed using an appropriate etching agent in the controlled regime and the amount of evo…
Effect of hydrogen peroxide on the dehydrogenase and quinone-reductase activity of irradiated Lactobacillus plantarum cells
Abstract The resistance of lactobacilli to oxidative stress is of great importance for their applicability as probiotics. This study aimed to evaluate the response of Lactobacillus plantarum strain ATCC® 14917™, grown in either de Man, Rogosa, and Sharpe agar (MRS medium) or tryptic soy broth (TSB medium), to 1–2 mM H2O2 after the exposure to different doses of ionising radiation. Two bacterial extracellular enzyme groups, dehydrogenases (DHAs) and quinone reductases (QRs), served as the criteria of viability and antioxidant activity, respectively. The irradiated L. plantarum culture grown in TSB showed increased QR activity at irradiation doses of 2–50 Gy, with the maximum activity at 10 G…
Tritium in plasma-facing components of JET with the ITER-Like-Wall
The role of radiolysis products in in situ luminescence of Li2O
Abstract A new phenomenon of an “excess luminescence” (EL) in Li 2 O observed at 4.5–2.5 eV under light ion (H + , He + ) irradiation during the rise of temperature (>573 K ) was studied. The essence of the EL is in the rapid pulse increase of the luminescence intensity. It is proposed that this phenomenon is based on the thermo-dissociation of colloidal Li into Li lattice ions, F + and F 0 centers, and oxygen vacancies. Formed oxygen vacancies capture electrons during the irradiation and form excited F-centers, whose relaxation gives the EL. This phenomenon was reproduced using X-ray irradiation and a sample containing colloidal Li introduced by irradiation with electron accelerator to an …
Influence of radiation defects on tritium release parameters from Li2O
Abstract The study of the influence of radiation defects on tritium release behavior from polycrystalline Li2O was performed by simultaneous measurements of the luminescence emission and tritium release. It was found that the radiation defects in Li2O introduced by electron irradiation cause the retention of tritium. It is thought that the tritium recovery is affected by the formation of a Li–T bond, which is tolerant of high temperatures. The retardation of tritium decreases with increasing absorbed dose in the dose range from 50 to 140 MGy. The aggregation of radiation defects at high irradiation doses is considered to be responsible for the decrease of the interaction of tritium with rad…
Simple Solution for Single Final Vial Filling of Ga-68 Radiopharmaceuticals in One Hot Cell Isolator at Small-Scale Radiopharmacy Laboratories under Aseptic Conditions
A simple solution for fulfilling biosafety and national drug agency demands of radiation and biosafety during Ga-68 radionuclide containing radiopharmaceutical production (RP) by small scale laboratories has been demonstrated based on a novel sterile seal concept of multi-layer bag system prototype. These mid-and inner enclosures of the prototype with vial inside were sterilized by 50 kGy of gamma radiation. The microbial safety validation based on two-week testing confirmed successful sterilization of the sealing bags with vails. The analysis of physicochemical properties, namely mechanical properties, gel fraction studies revealed that sterilization did not cause any undesired changes in …
Radiation-induced effects in neutron- and electron-irradiated lithium silicate ceramic breeder pebbles
Abstract Ceramic breeder (CB) pebbles consisting of lithium orthosilicate (Li4SiO4) as the main phase and lithium metasilicate (Li2SiO3) as a secondary phase were analysed with respect to radiation-induced defects and radiolysis products. Therefore, pebbles that were irradiated with neutrons in the so-called HICU experiment ( H igh neutron fluence i rradiation of pebble sta c ks for f u sion) were compared to pebbles irradiated with accelerated electrons and to an unirradiated sample. Fourier transformation infrared spectroscopy was used to investigate changes in the phase composition. Beside an expected increase in the second phase in the neutron-irradiated samples, no further significant …
Influence of chemisorption products of carbon dioxide and water vapour on radiolysis of tritium breeder
Abstract Lithium orthosilicate pebbles with 2.5 wt% excess of silica are the reference tritium breeding material for the European solid breeder test blanket modules. On the surface of the pebbles chemisorption products of carbon dioxide and water vapour (lithium carbonate and hydroxide) may accumulate during the fabrication process. In this study the influence of the chemisorption products on radiolysis of the pebbles was investigated. Using nanosized lithium orthosilicate powders, factors, which can influence the formation and radiolysis of the chemisorption products, were determined and described as well. The formation of radiation-induced defects and radiolysis products was studied with …
Comparison of the structure of the plasma-facing surface and tritium accumulation in beryllium tiles from JET ILW campaigns 2011-2012 and 2013-2014
In this study, beryllium tiles from Joint European Torus (JET) vacuum vessel wall were analysed and compared regarding their position in the vacuum vessel and differences in the exploitation conditions during two campaigns of ITER-Like-Wall (ILW) in 2011-2012 (ILW1) and 2013-2014 (ILW2) Tritium content in beryllium samples were assessed. Two methods were used to measure tritium content in the samples - dissolution under controlled conditions and tritium thermal desorption. Prior to desorption and dissolution experiments, scanning electron microscopy and energy dispersive x-ray spectroscopy were used to study structure and chemical composition of plasma-facing-surfaces of the beryllium sampl…
Tritium localisation and release from the ceramic pebbles of breeder
Magnetic field (MF) effects on the radiolysis and tritium release from Li4SiO4 (FZK) and Li2TiO3 (CEA) ceramic pebbles were investigated. The tritium chemical forms in Li4SiO4 were estimated by means of lyomethods. In the case of the neutron fluence Fn 6 10 18 nm � 2 , the tritium is mostly in the T þ form, but in the case of Fn � 10 25 nm � 2 , the T þ form accounts for 86–95% of the tritium. A high subsurface concentration of tritium is characteristic of a separate pebble and correlates with the distribution of radiation-induced defects. The MF increases the radiolysis of Li4SiO4 by 20–25%. Irradiation with electrons to 1000 MGy at 1200 K increases the grain size by 5–10%, decreasing the …
Effect of Isothiocyanates on the Activity of <i>Lactobacillus plantarum</i> Exposed to Irradiation
Two isothiocyanates, i.e., sulforaphane (SFA) and sulforaphene (SFE), are suggested to be used as an alternative chemopreventive diet. This study was focused on the effect of SFA and SFE on Lactobacillus plantarum, which has been subjected to the irradiation (2-50 Gy). The cultures grown in De Man, Rogosa and Sharpe (MRS) and Tryptone Soya Broth (TSB) were compared in terms of bacteria physiological activity under tested conditions. Broth composition notably influenced the bacteria growth kinetic parameters, as well as culture response to the oxidative stress. Activity of L. plantarum cells after irradiation was evaluated by their dehydrogenase (DHA) and quinone-reductase (QR) activities. T…
Laser irradiation of carbon–tungsten materials
Carbon–tungsten layers deposited on graphite by thermionic vacuum arc (TVA) were directly irradiated with a femtosecond terawatt laser. The morphological and structural changes produced in the irradiated area by different numbers of pulses were systematically explored, both along the spots and in their depths. Although micro-Raman and Synchrotron-x-ray diffraction investigations have shown no carbide formation, they have shown the unexpected presence of embedded nano-diamonds in the areas irradiated with high fluencies. Scanning electron microscopy images show a cumulative effect of the laser pulses on the morphology through the ablation process. The micro-Raman spatial mapping signalled an…
Tritium retention in plasma facing materials of JET ITER-Like-Wall retrieved from the vacuum vessel in 2012 (ILW1), 2014 (ILW2) and 2016 (ILW3)
Abstract ITER-Like-Wall (ILW) project has been carried out at Joint European Torus (JET) to test plasma facing materials relevant to International Thermonuclear Experimental Reactor – ITER [1]. Limiters and an upper dump plate of the vacuum vessel are made of bulk beryllium tiles, whereas for the divertor bulk tungsten and tungsten-coated carbon fibre (CFC) composite tiles are used. During the shutdowns in ILW1 (2012), ILW2 (2014) and ILW3 (2016), selected beryllium tiles were removed from the vacuum vessel. In this study, tiles from three positions were analysed, and analysis results were compared regarding both the tile position in the vacuum vessel and differences in the exploitation con…
X-ray induced defects in advanced lithium orthosilicate pebbles with additions of lithium metatitanate
Abstract Advanced lithium orthosilicate (Li4SiO4) pebbles with additions of lithium metatitanate (Li2TiO3) as a secondary phase have attracted international attention as an alternative solid-state candidate for the tritium breeding in future nuclear fusion reactors. In this research, the generation of radiation-induced defects in the Li4SiO4 pebbles with various contents of Li2TiO3 was analysed in-situ by X-ray induced luminescence technique. After irradiation with X-rays, the accumulated radiation-induced defects in the Li4SiO4 pebbles were studied by electron spin resonance, thermally stimulated luminescence and absorption spectrometry. On the basis of the obtained results, it is conclude…
Luminescence of X-ray induced radiation defects in modified lithium orthosilicate pebbles with additions of titanium dioxide
The authors greatly acknowledge the technical and experimental support of O. Leys, M. H. H. Kolb, and R. Knitter (Karlsruhe Institute of Technology, Germany). 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 Economics”.
Comparison of tritium measurement techniques for a laser cleaned JET tile
Abstract Over the last 7–8 years, two quantitative analyzing methods—accelerator mass spectrometry (AMS) and full combustion (FC) followed by scintillation detection have been applied for determining the tritium activity concentrations in JET divertor tiles. These methods have two main differences – the range of detection and the spatial resolution – and are thus complementary. However, these differences can also complicate the comparison of the two techniques for typical JET divertor samples. Therefore a cross comparison exercise for tritium measurements was performed between the two methods using specially produced identical standard samples. The cross comparison measurements were perform…
Investigation of hydrogen and deuterium impact on the release of tritium from two-phase lithium ceramics under reactor irradiation
In the development of fusion energy, an important task is the study and improvement of tritium production technologies. In this case, one of the most promising materials for tritium generation is lithium ceramics. Considering the importance of the task, numerous studies are aimed at solving the problem of determining the parameters and mechanisms of tritium release in lithium-containing materials. This paper presents the results of a study of tritium release processes from two-phase lithium ceramics of Li$_{4}$SiO$_{4}$/Li$_{2}$TiO$_{3}$ during reactor irradiation when hydrogen and deuterium are injected into the chamber with irradiated samples. The mechanisms regularities of the tritium yi…
Behaviour of neutron irradiated beryllium during temperature excursions up to and beyond its melting temperature
Abstract Beryllium pebble behaviour has been studied regarding the accidental operation conditions of tritium breeding blanket of fusion reactors. Structure evolution, oxidation and thermal properties have been compared for nonirradiated and neutron irradiated beryllium pebbles during thermal treatment in a temperature range from ambient temperature to 1600 K. For neutron irradiated pebbles tritium release process was studied. Methods of temperature programmed tritium desorption (TPD) in combination with thermogravimetry (TG) and temperature differential analysis (TDA), scanning electron microscopy (SEM) in combination with Energy Dispersive X-ray analysis (EDX) have been used. It was found…
Overview of the JET results in support to ITER
The 2014–2016 JET results are reviewed in the light of their significance for optimising the ITER research plan for the active and non-active operation. More than 60 h of plasma operation with ITER first wall materials successfully took place since its installation in 2011. New multi-machine scaling of the type I-ELM divertor energy flux density to ITER is supported by first principle modelling. ITER relevant disruption experiments and first principle modelling are reported with a set of three disruption mitigation valves mimicking the ITER setup. Insights of the L–H power threshold in Deuterium and Hydrogen are given, stressing the importance of the magnetic configurations and the recent m…
Tritium retention measurements by accelerator mass spectrometry and full combustion of W-coated and uncoated CFC tiles from the JET divertor
Abstract Accelerator mass spectrometry (AMS) and the full combustion method (FCM) followed by liquid scintillation counting were applied to quantitatively determine the tritium retention in the tungsten-coated carbon fibre composites (CFC), in comparison to uncoated CFC tiles from the JET divertor. The tiles were adjacent and exposed to plasma operations between 2007 and 2009. The tritium depth profiles are showing that the tritium retention on the W-coated tile was reduced by a factor of 13.5 in comparison to the uncoated tile whereas the bulk tritium concentration is approximately the same for both tiles.
Growth of beryllium oxide nano-structures during thermal treatment of neutron irradiated beryllium
Beryllium oxide nano-structures grown during high temperature oxidation of neutron irradiated beryllium has been investigated. Oxidation of non - irradiated and neutron irradiated beryllium was performed in differential thermal analyzer in an atmosphere of air and its mixture with helium at temperatures up to 1050°C. Structure of beryllium and its oxide was studied by the means of scanning electron microscopy. The growth of beryllium oxide nano-structures – “labyrinth type” layers and nano-rods on the inner surfaces of neutron irradiated beryllium were observed by means of Scanning Electron Microscopy. The size of the rods was 10-100 nm in diameter and up to few micrometers in length. There…
Tritium distribution and chemical forms in the irradiated beryllium pebbles before and after thermoannealing
Abstract Beryllium pebbles are foreseen as a neutron multiplier in the tritium breeding blanket of the future fusion devices. Tritium inventory in the beryllium as a result of neutron-induced transmutations is a significant safety and technological issue for the operation of the breeding blanket. In this study, beryllium pebbles from 3 different irradiation experiments: BERYLLIUM, EXOTIC 8/3-13 and PBA, performed at High Flux Reactor HFR have been investigated. The distribution of tritium in the bulk of the pebbles and the abundance ratios of chemical forms of tritium T 0 , T + and T 2 have been analysed before and after the different thermo-annealing experiments. In order to determine the …
Basic study of influence of radiation defects on tritium release processes from lithium silicates
The radiolysis of Li2SiO3 and Li4SiO4 was studied using the chemical scavengers method (CSM), thermoluminescence, lyoluminescence, electron spin resonance and spectrometric methods. The influence of the absorbed dose and many another parameters such as: irradiation conditions, sample preparation conditions and concentration of impurities on the accumulation rate of each type RD and RP were studied. Several possibilities for reducing the radiolysis of silicates were discussed. It has been found that tritium localization on the surface and in grains proceed by two different mechanisms. Tritium thermoextraction from the surface proceeds as chemidesorption of tritiated water, but from the bulk …
Surface Morphology of Single and Multi-Layer Silicon Nitride Dielectric Nano-Coatings on Silicon Dioxide and Polycrystalline Silicon
Silicon nitride (Si3N4) in a form of single and multi-layer nanofilms is proposed to be used as a dielectric layer in nanocapacitors for operation in harsh environmental conditions. Characterization of surface morphology, roughness and chemical bonds of the Si3N4 coatings has an important role in production process as the surface morphology affects the contact surface with other components of the produced device. Si3N4 was synthesized by using low pressure chemical vapour deposition method and depositing single and multi-layer (3 – 5 layers) nanofilms on SiO2 and polycrystalline silicon (PolySi). The total thickness of the synthesized nanofilms was 20 – 60 nm. Surface morphology was investi…
Experimental setup for analysis of sorption and desorption of tritium in liquid lithium under different external conditions
An original complex device has been designed and created specially for this research. Some of tritium sorption and thermal desorption in liquid lithium experiments has been successfully done already. First experiment series were carried out under reduced pressure (vacuum) to rule out other operating gases (like Ar) that may squeeze out tritium from lithium. Experiments showed good tritium desorption from lithium which highly depends on the temperature. A proportional gas counter tritium monitor was used to collect data from tritium thermal desorption experiments.
Experiments on tritium generation and yield from lithium ceramics during neutron irradiation
Abstract The vacuum extraction method with a mass spectrometry registration of tritium is presented in paper. It can provide a full-range analysis of gas phase composition in the chamber with samples under neutron irradiation. Lithium ceramics Li2TiO3 in the form of pebbles with lithium enrichment on 6Li isotope of 96% was examined. The paper shows the results of reactor experiments on study the extraction of tritium-containing molecules from lithium ceramics Li2TiO3 at various temperatures and reactor power levels at the WWR-K research reactor (Almaty, Kazakhstan). The time dependences of tritium yield from the ampoule with ceramics during reactor irradiation were obtained. Near-surface co…
Influence of Biomass Combustion Products on Element Content and Thermal Stability of Latvian Sheep Breed Wool Filter Fibres
Sheep wool is natural, easy obtainable, renewable and biodegradable material with a perspective application as a sorbent in filters for purification of industrial emissions from various environmental pollutants. The element content and thermal stability of Latvian dark-headed sheep wool filter fibres was analysed and described before and after exposure to biomass combustion products. Based on the obtained results, it is concluded that the sheep wool filter fibres can sorb various gaseous combustion products, such as carbon monoxide (CO), carbon dioxide (CO2) and nitrogen oxides (NOx), however, the sorption processes of these gases are irreversible. The obtained results of total reflection X…
Improvement of mechanical and dielectric properties of ethylene–octene copolymer by multi‐walled carbon nanotubes functionalized with poly(2,2′‐bithiophene)
Investigations of Latvian Illite/Kaolinite Clays Irradiated Under Action of Accelerated Electrons
Natural clay is a perspective material for application as sorbents for wastewater treatment as well as for sorption of radionuclides, where the properties of the clays can be changed under influence of ionizing radiation. For application of Latvian illite/kaolinite clays for isotope sorption it is important to characterize the physic-chemical properties of pre-prepared air dried clays. Two fractions of the illite clays were selected. A fraction with grain size 100 μm (SiO2 content 60.9 ± 1.5 wt.%, specific surface area 35 m2/g) and a sand free fraction – 2 μm (SiO2 47.7 ± 1.9 wt.%, specific surface area 38 m2/g). Selected fractions were irradiated with accelerated electrons (5 MeV, ELU-4, S…
Accumulation of radiation defects and products of radiolysis in lithium orthosilicate pebbles with silicon dioxide additions under action of high absorbed doses and high temperature in air and inert atmosphere
Abstract One of the technological problems of a fusion reactor is the change in composition and structure of ceramic breeders (Li 4 SiO 4 or Li 2 TiO 3 pebbles) during long-term operation. In this study changes in the composition and microstructure of Li 4 SiO 4 pebbles with 2.5 wt% silicon dioxide additions, fabricated by a melt-spraying process, were investigated after fast electron irradiation ( E = 5 MeV, dose rate up to 88 MGy h −1 ) with high absorbed dose from 1.3 to 10.6 GGy at high temperature (543–573 K) in air and argon atmosphere. Three types of pebbles with different diameters and grain sizes were investigated. Products of radiolysis were studied by means of FTIR and XRD. TSL …