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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
21

Analyse et spéciation du tritium dans des matrices environnementales / Analysis and spéciation of the tritium in environmental matrices

Bacchetta, Audrey 28 January 2014 (has links)
Cette étude s'inscrit dans le domaine de la surveillance de l'environnement. Elle consiste à optimiser et valider la procédure analytique de détermination du tritium sous forme organique, et à identifier les molécules organiques, porteuses de tritium, responsables de son transfert de l'environnement à l'homme. La démarche s'est organisée en trois temps. Une procédure analytique a d'abord été mise en place pour déterminer, la teneur en hydrogène des échantillons, élément clé, utilisée pour le calcul des activités de tritium organique. L'impact de la séparation des fractions de tritium organique (l'échange labile) sur la détermination de l'activité de la fraction représentative du niveau de tritium environnemental a ensuite été évalué. Pour cela, les quantités d'échantillon solubilisées ont été estimées. Enfin, la spéciation du tritium dans des échantillons environnementaux a été abordée. Pour cela, les familles de molécules, puis les composés organiques solubilisés lors des échanges labiles ont été identifiés. Les résultats montrent que la répartition du tritium dans les organismes dépend à la fois des propriétés de la liaison chimique dans laquelle il est impliqué et des propriétés des molécules organiques le portant. Les composés identifiés appartiennent aux familles de molécules constitutives (glucides, acides aminés) de la matière vivante. Il serait à présent intéressant d'étudier la répartition du tritium au sein d'un échantillon de l'environnement pour cibler les molécules d'intérêt et étudier de manière plus approfondie la distribution du tritium dans l'environnement et son impact, de l'environnement à l'homme. / This study deals with environmental monitoring. The main aims are (i) the optimisation of the analytical procedure for the tritium in organic form determination, and (ii) the identification of the tritium bearing molecules which are responsible for its transfer from the environment to man. The study was divided into three stages. First an analytical method was developed to determine hydrogen content of several samples, which is a key element to calculate accurate organically bound tritium activities. Secondly, the impact of the organically bound tritium fractions separation (labile exchange) for the determination of the representative fraction of the level of environmental tritium activity was then evaluated. For that, the amount of solubilised sample was estimated. Finally, the speciation of tritium in environmental samples was investigated. Several molecules classes and organic compounds dissolved in the labile exchanges solvent were identified. The results show that the distribution of tritium in organisms depends on both properties of the chemical bond in which it is involved and chemical properties of tritium bearing molecules. The identified compounds belong to the molecules classes such as carbohydrates or amino acids, constitutive of living organisms. It would now be of interest to study the tritium distribution in an environmental sample to target molecules of interest and study the impact of tritium from the environment to man.
22

Activation of Organically-Bound Tritium by Tritiated Water in Soil

Shkarupin, Aliaksei 03 July 2019 (has links)
The fate of tritium in the environment is a target of interest in many studies. However reported concentrations of organically bound tritium (OBT) in soil are not well understood. In this study, a supplementary non-biological process of soil OBT activation in the environment was explored. The vicinity of SRB Technologies (Pembroke, Ontario) was chosen as the sampling location because of a significant airborne tritium release prior to 2001 which resulted in groundwater contamination. Soil cores were extracted from the ground near the tritium-releasing facility stack in 2017 and split into 10 cm subsamples for HTO/OBT, total carbon and hydrogen, particle size, thermogravimetric, radiocarbon and 3He mass spectrometry analyses. Observed HTO profiles revealed elevated tritium concentrations still retained in the soil. The results indicated that clay bound tritium masks the OBT signal and cannot be easily distinguished. Multiple short-term sample rinses with tritium-free water have little effect on clay bound water removal. Therefore, clay bound tritium should to be addressed in any future research related to soil OBT.
23

Origine et devenir du tritium au sein des hydrosystèmes continentaux méditerranéens français / Origin and fate of tritium in fresh water systems in the South-East of France

Ducros, Loïc 14 June 2018 (has links)
Initialement émis lors des essais nucléaires atmosphériques, le tritium (3H) est l’un des principaux radionucléides rejetés par les installations nucléaires. Il est présent dans toutes les composantes environnementales sous différentes formes, libres (HT, HTO, CH3T) ou liée à la matière organique (TOL). Le tritium suit les mêmes dynamiques d’incorporation et de dégradation dans les organismes que l’hydrogène et se met rapidement à l’équilibre avec le milieu ambiant. Des études ont montré un déséquilibre TOL/HTO dans différents compartiments et matrices environnementales. Ce travail vise à expliquer la variabilité des concentrations en 3H et l’origine des déséquilibres observés en se basant sur l’hypothèse de la rémanence. Une approche multi-échelles axée sur le rôle du transfert différé de la matière organique entre les compartiments environnementaux a été menée. Les résultats acquis ont permis d’établir des gammes de concentrations en HTO dans des cours d’eau non influencés par des rejets tritiés et d’identifier les principaux paramètres liés à la variabilité observée. Les résultats ont aussi permis de comprendre l’origine du TOL à partir d’analyses statistiques, qui tendent à confirmer que des zones de rémanence en TOL issus des essais nucléaires, peuvent conduire à des déséquilibres significatifs entre formes libre et liée. De plus, l’étude d’une archive sédimentaire a montré l’existence d’un pic de concentrations en TOL en profondeur, provenant vraisemblablement des retombées de ces essais. Enfin, l’instrumentation d’un site atelier, à proximité d’installations nucléaires, a permis de confirmer l’existence d’un marquage de la matière organique et la rémanence du TOL. / Initially emitted in the environment by atmospheric nuclear weapons tests, tritium (3H) is one of the main radionuclide released by nuclear facilities. It is present in all environmental media in several different forms, bound to organic matter (OBT) or in free forms (HT, HTO, CH3T). Furthermore, 3H follows the same dynamics of incorporation and degradation in living organisms as the hydrogen and is quickly balanced with the surrounding environment. Numerous studies have shown disequilibrium of OBT/HTO in different environmental compartments and matrices. This research work aims to explain the variability of 3H concentrations and the origin of disequilibrium of OBT/HTO based on the persistence hypothesis. In this study, a multi-scale approach was used, focusing on the role of delayed transfer of organic matter between natural compartments. The main results have established the ranges of HTO concentrations in several rivers that are not influenced by atmospheric releases from nuclear facilities, and also identified key environmental parameters linked to the observed variability. The results also made it possible to understand the origin of OBT using statistical analyses. The results tend to confirm that atmospheric nuclear tests led to areas of persistence of OBT, and can lead to significant disequilibrium between bound and free forms. Moreover, the study of a sediment core has shown a peak of OBT at depth, in all likelihood from the global fallout associated with atmospheric nuclear weapons tests. Also, a study site impacted by industrial releases of tritium for the last fifty years has confirmed the persistence of OBT in organic matter, especially in abiotic matrices.
24

Development of methods to improve knowledge of tritium inputs to the ocean

Stark, Sheila January 2003 (has links)
No description available.
25

Uncertainty in historical tritium releases for dose reconstruction at the Savannah River Site

Lee, Patricia L. 08 1900 (has links)
No description available.
26

Tritiumspeicherung in ZrCo

Besserer, Uwe Alwin. Unknown Date (has links)
Universiẗat, Diss., 2003--Marburg.
27

Studium okrajového plazmatu Tokamaku a jeho interakce s první stěnou / Studies of tokamak edge plasma and its interaction with the first wall

Komm, Michael January 2011 (has links)
Title: Studies of tokamak edge plasma and its interaction with the first wall Author: Michael Komm Department: Department of Surface and Plasma Science Thesis director: doc. Mgr. Pavel Kudrna, Dr. KFPP Thesis supervisor: Dr. Renaud Dejarnac, IPP CAS CR Abstract: This work presents results of simulations of nuclear fusion related problems, using both 2D PIC code (SPICE2) and full 3D code (SPICE3). The simulations allowed us to predict particle and heat loads coming from plasma onto the divertor tiles, which is a key problem for the next-step de- vices. The results of simulations contributed to the research of fuel retention in the gaps between divertor tiles. We we also able to explain the behaviour of the Katsumata probe and verify the validity of its measurements. Keywords: Tokamak, PIC, divertor, tritium, Katsumata
28

Aplicacao e avaliacao da tecnica de marcacao da umidade do solo com tritio artificial em pesquisas hidrogeologicas no Brasil

POLI, DORA de C.R. 09 October 2014 (has links)
Made available in DSpace on 2014-10-09T12:36:14Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T13:59:20Z (GMT). No. of bitstreams: 1 03767.pdf: 3353375 bytes, checksum: 1ea721cc89ae368c52ddebfefd7952b1 (MD5) / Tese (Doutoramento) / IPEN/T / Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP
29

Determinacao de uranio e tritio em urina de trabalhadores

PASSARELLI, MIRIAM M. 09 October 2014 (has links)
Made available in DSpace on 2014-10-09T12:25:16Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:03:12Z (GMT). No. of bitstreams: 1 01248.pdf: 1789417 bytes, checksum: 5a973aecd1016836db674f63b72e6524 (MD5) / Dissertacao (Mestrado) / IEA/D / Faculdade de Ciencias Farmaceuticas, Universidade de Sao Paulo - CF/USP
30

Aplicacao e avaliacao da tecnica de marcacao da umidade do solo com tritio artificial em pesquisas hidrogeologicas no Brasil

POLI, DORA de C.R. 09 October 2014 (has links)
Made available in DSpace on 2014-10-09T12:36:14Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T13:59:20Z (GMT). No. of bitstreams: 1 03767.pdf: 3353375 bytes, checksum: 1ea721cc89ae368c52ddebfefd7952b1 (MD5) / Tese (Doutoramento) / IPEN/T / Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP

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