0000000000285025
AUTHOR
Sylver Heinze
Relation between grain size and hydrogen diffusion coefficient in an industrial Pd–23% Ag alloy
Abstract The diffusion mechanism of hydrogen in an industrial cold worked Pd–23% Ag alloy is investigated according to its grain size. The microstructural parameters are determined by X-ray diffraction analysis and the diffusion parameters are determined using the galvanostatic electrochemical permeation technique. Two diffusion mechanisms are displayed. For apparent grain size below 40 nm the hydrogen atoms diffuse in the grain boundaries. For grain size above 100 nm, an intergranular diffusion mechanism occurs. For intermediate grain size both mechanisms coexist. Furthermore, the diffusion in the grain boundaries is not faster than the diffusion in the bulk, as generally observed for pure…
Self radiolysis of tritiated water
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…
Bipolar electrolysis for tritium recovery from weakly active tritiated water
Abstract Detritiation facilities produce low activity tritiated water from which tritium cannot be recovered. Bipolar electrolysis, based on the electrochemical permeation of hydrogen and its isotopes through Pd–Ag alloy membranes, allows tritiated water enrichment together with negligible gaseous tritium release. Our purpose is to enrich water from 500 Ci/l (1.85×1013 Bq/l) to more than 2000 Ci/l (7.40×1013 Bq/l). We first describe the principle of bipolar electrolysis and its application to isotopic enrichment. The experimental part of this work consists of the determination of the isotopic separation factors. From these experimental values, we simulated the working of an operational cell…
Self-Radiolysis of Tritiated Water: Experimental Study and Simulation
Radioactive decay of tritium contained in tritiated water leads to the production of gaseous helium and, through self-radiolysis, to the formation of molecular hydrogen and oxygen. For safety management of tritiated water storage, it is essential to be able to predict pressure increase resulting from this phenomenon. The present study aims to identify the mechanisms that take place in self-radiolysis of chemically pure liquid tritiated water. The evolution of the concentration of hydrogen and oxygen in the gas phase of closed vessels containing tritiated water has been followed experimentally. Simulation of pure water radiolysis has been carried out using data from the literature. In order …