Graduation date: 1968

No description available.

No description available.

A Gerência de Rejeitos Radioativos do IPEN já se utiliza da técnica de ablação por laser para descontaminação de peças superficialmente contaminadas por material radioativo. Esta tecnologia, porém, demonstrou grande potencial para caracterização destes rejeitos com o objetivo de levantar o Inventário Radioisotópico de peças. As técnicas atuais para levantar este inventário (esfregaço e modelagem físico-matemática) sofrem de grandes limitações de implementação e de precisão. O objetivo deste trabalho é desenvolver o projeto de uma sonda de ablação por laser acoplada a um módulo de sucção e captura por filtro do particulado ejetado na ablação, permitindo envio do filtro para análise de emissões radioativas para classificação de radioisótopos. / The department Gerência de Rejeitos Radioativos (Radioactive Waste Management) from IPEN has already used the laser ablation technique for superficial decontamination of parts. This technique has also shown great potential for characterization of this waste with the purpose of rising data for the Radioisotopic Inventory of parts. The current techniques for this purpose (wipe sampling and physical modeling) lack the accuracy and practicality. The objective of this study is to develop the project of an instrument of laser ablation engaged with a module for sucking and capturing (by filter) the particulate ejected from the ablation, allowing the filter to be analyzed in laboratory for radioisotopic classification through radioactive emission.

Diss. (sammanfattning). Uppsala : Sveriges lantbruksuniv., 2003. / Härtill 5 uppsatser.

Diss. (sammanfattning) Uppsala : Sveriges lantbruksuniv. / Härtill 4 uppsatser.

Concentration ratios are used to determine the transfer of nuclides from soil to biota to fauna. Some nuclides have limited associated data though, this has not prevented predictions from being performed at sites without associated data. These ratios are site specific and are not fully applicable when applied to other locations. A recent literature review for a waste repository performance assessment determined that a significant portion of the environmental data was based on recursively published material. To address this deficiency neutron activation analysis (NAA) was used to determine concentration ratios of certain biota. Three sites, two riparian and one shrub steppe, were sampled in the eastern Washington Columbia basin, near the Hanford site. Two hundred and fifty eight samples of opportunity were collected. This included 15 soil samples, 10 water and sediment samples, 40 different species of biota, and 2 terrestrial animal species and 3 aquatic animal species. These samples were prepared for NAA by drying, weighing, and in certain cases ashing to improve detection efficiency. After activation, the samples were placed in a HPGe detector to perform spectral analysis. The concentration results of 26 elements of interest are presented, along with newly established concentration ratios for all of the species sampled. / Graduation date: 2013

Pour un réacteur à eau pressurisée, la contamination radioactive du circuit primaire constitue un problème majeur pour les opérations de maintenance. La principale source de cette contamination est le relâchement des produits de corrosion des tubes GV en alliages base nickel représentant environ les trois quarts de la surface totale du circuit primaire. L’oxydation des alliages base nickel en milieu primaire, à l’origine du relâchement, a fait l’objet de nombreuses études. Certaines pistes d’amélioration ont d’ailleurs d’ores et déjà été explorées comme la métallurgie des tubes et plus précisément leur état de surface, la pré-oxydation, l’addition de zinc au sein du milieu primaire. Cependant, la compréhension du phénomène demeure lacunaire. La nature et la structure de la couche d’oxyde formée sur les alliages base nickel est relativement bien connue, mais pas sa cinétique de formation et de relâchement ou de façon bien moins précise. L’objet principal de cette étude est donc le développement et la mise en œuvre d’un dispositif expérimental innovant permettant de suivre l’épaisseur d’oxyde formée par une mesure optique de réflectométrie in situ, ainsi que le relâchement en ligne par mesure de concentration par ICP – MS. Les échantillons utilisés lors des différents essais expérimentaux ont également été analysés par diverses techniques notamment l’XPS et le MET afin d’apporter de nouveaux éléments sur la nature ou la structure des couches d’oxyde. En outre, ces analyses, permettant également d’évaluer les épaisseurs d’oxyde ont contribué à valider les résultats d’oxydation obtenus par réflectométrie. L’utilisation de ce moyen expérimental a permis d’obtenir des résultats, certes peu nombreux mais aux perspectives prometteuses. / The radioactive contamination is a significant issue for the maintenance of the primary loop of a water pressurized reactor. The corrosion products released by steam generators tubes made of nickel base alloys, which represent seventy five percent of the whole primary loop surfaces, are highly responsible for this pollution. The oxidation of nickel base alloys in primary water is thus a widely studied subject. Besides, some mitigation means have already been performed like the control of tube manufacturing and of their surface state in particular, a pre-oxidation process, the injection of zinc into primary water. However, the phenomenon remains deficiently understood. The oxide layer nature and structure, formed on nickel base alloys is relatively well known, but this knowledge is far less precise about the layer formation and release kinetics. The main subject of this study is thus to develop an innovative experimental facility which permits to obtain the layer thickness by in situ optical reflectometry measurements, and the corrosion products release by concentration ICP – MS in line measurements. The implementation of these two techniques has needed lots of theoretical and technical adjustments, especially in situ way of using the reflectometry. Some analyses, XPS and MET in particular, have been performed on the different used samples to bring new facts about the nature and structure of oxide layers. Moreover, these analyses have contributed to validate the oxidation results, by measuring the oxide layer thickness and comparing it to the reflectometric results. The different tests realized with this new experimental device are quite promising and should be used and improved to perform others valuable tests.