Search results for "nuclear energy"
showing 10 items of 614 documents
Glovebox atmosphere detritiation process using gas separation membranes.
2003
Abstract The use of gas separation membranes in atmospheric detritiation systems has been studied. The main advantage of this new process is to reduce the number and/or the size of the equipment in comparison to conventional tritium removal systems. Owing to the constraints linked to tritium handling, the separation performances of several commercial hollow fiber organic membranes have been analyzed, under various operating conditions, with hydrogen/nitrogen or deuterium/nitrogen mixtures. The experiments are performed with small quantities of hydrogen or deuterium (5000 ppm). The experimental results allow to evaluate the separation efficiency of these membranes and to determine the approp…
Self radiolysis of tritiated water
2003
The mechanism of water radiolysis implies several reactions and depends on many parameters such as the radiation characteristics (type of radiation, energy…), the temperature and the chemical composition of irradiate water. Thus it is very difficult to foresee, without experimental data, the overall effect of these parameters. If radiolysis of pure water under γ rays or α particles has been widely studied, it is not the case for self radiolysis of tritiated water (low energy β− particles radiation). In order to fill this lack of experimental knowledge and to understand the radiolysis of stored tritiated water produced in tritium plants, we studied the evolution of hydrogen and oxygen concen…
Characterisation and radiolysis of modified lithium orthosilicate pebbles with noble metal impurities
2017
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),…
Effects of the cycling workload on core and local skin temperatures
2016
[EN] Purpose: The aim of the study was to determine the influence of cycling workload on the variation of core and skin temperature of the different body regions, and the relationship between both temperature variables. Method: Fourteen cyclists performed two 45-min cycling tests at 35% and 50% of peak power output on different days. The cadence was constant in both tests (90 rpm). Core temperature was measured continuously throughout the test and local skin temperature was recorded before, immediately after and 10 min after finishing the cycling test. Differences in variation of the core and skin temperature and in the effort perception and body mass loss due to different cycling workload …
How the formation of interfacial charge causes hysteresis in perovskite solar cells
2018
In this study, we discuss the underlying mechanism of the current-voltage hysteresis in a hybrid lead-halide perovskite solar cell. We have developed a method based on Kelvin probe force microscopy that enables mapping charge redistribution in an operating device upon a voltage- or light pulse with sub-millisecond resolution. We observed the formation of a localized interfacial charge at the anode interface, which screened most of the electric field in the cell. The formation of this charge happened within 10 ms after applying a forward voltage to the device. After switching off the forward voltage, however, these interfacial charges were stable for over 500 ms and created a reverse electri…
Modeling of ITER TF cooling system through 2D thermal analyses and enthalpy balance
2017
Abstract The winding pack of the ITER Toroidal Field (TF) coils is composed of 134 turns of Nb3Sn Cable in Conduit Conductor (CICCs) wound in 7 double pancakes and cooled by supercritical helium (He) at cryogenic temperature. The cooling of the Stainless Steel (SS) case supporting the winding pack is guaranteed by He circulation in 74 parallel channels. A 2D approach to compute the temperature distribution in the ITER TF winding pack is here proposed. The TF is divided in 32 poloidal segments, for each segment the corresponding 2D model is built and a thermal analysis is performed applying the corresponding nuclear heating computed with MCNP code considering the latest design updates, such …
Behaviour of tritium in breeding materials
2005
Abstract The tritium release from ceramic materials of the HCPB under real DEMO operating conditions will depend not only on temperature and neutron flux but also on an intense magnetic field (MF) of 7–9 T. The delay in the tritium release induced by the MF is proportional to the grain size of the ceramics, the squared MF intensity and the abundance ratio of charged tritium forms (T + , T − ) in the grain volume of the ceramics. The effect of MFs of different intensity on the tritium release from the Li 4 SiO 4 pebbles irradiated in the EXOTIC-8 experiment (neutron fluence 2.4 × 10 25 n m −2 , irradiation temperature up to 700 K) was investigated in this study. As a result of the irradiati…
Influence of chemisorption products of carbon dioxide and water vapour on radiolysis of tritium breeder
2014
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 …
Physicochemical processes in blanket ceramic materials
2003
Abstract Effect of external magnetic field (MF) on important physicochemical processes in ceramic blanket materials, the Li4SiO4 (FZK) and Li2TiO3 (CEA) ceramic pebbles, was studied. Stoichiometric amounts of the radiation-induced defects (RD) of the electron and hole type form at radiolysis of the ceramic materials. Colloid lithium forms only in Li4SiO4 under irradiation at the temperature 423–473 K and the dose 10–20 MGy. The magnetic field increases the radiolysis efficiency by 20–25% in both materials. The efficiency of formation of RD decreases with the increasing temperature of irradiation. Complete recombination of RD takes place at 873 K. The magnetic field retards the tritium relea…
X-ray induced defects in advanced lithium orthosilicate pebbles with additions of lithium metatitanate
2019
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…