0000000001266346
AUTHOR
A. Supe
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”.
Characterisation and radiolysis of modified lithium orthosilicate pebbles with noble metal impurities
Modified lithium orthosilicate (Li4SiO4) pebbles with additions of titanium dioxide (TiO2) are suggested as an alternative tritium breeding ceramic for the European solid breeder test blanket module. The noble metals – platinum (Pt), gold (Au) and rhodium (Rh), can be introduced into the modified Li4SiO4 pebbles during the melt-based process, due to the corrosion of Pt-Rh and Pt-Au alloy crucible components. In this study, the surface microstructure, chemical and phase composition of the modified Li4SiO4 pebbles with different contents of the noble metals was analysed. The influence of the noble metals on the radiolysis was evaluated after irradiation with accelerated electrons (E = 5 MeV),…
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 …
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…
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 …
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”.
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 …
FIBRE OPTICAL COUPLER SIMULATION BY COMSOL MULTIPHYSICS SOFTWARE
Funding: The research has been supported by the European Regional Development Fund project No.1.1.1.1/18/A/068. The Institute of Solid State Physics, University of Latvia as a 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 CAMART2.
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 …