A new discriminating high temperature fission chamber filled with xenon designed for sodium-cooled fast reactors

Xenon high temperature fission chamber, designed for sodium-cooled fast reactors, unlike the argon filled fission chambers, can operate at temperatures greater than 500◦C without partial-discharges and discriminate neutrons and partial-discharges at temperatures up to 650◦C

Paschen’s law in extreme pressure and temperature conditions

Paschen’s law gives the inception voltage for an electrical discharge as a function of the product of gas pressure and the gap distance between two infinite planar electrodes. It is known that deviations from Paschen’s law occur when temperature is increased. Historically two theoretical corrections, the Peek and Dumbar corrections, are proposed to predict the deviation from Paschen’s law by increasing temperature. To carry out an experimental investigation on the deviation from Paschen’s law by increasing temperature a customized system was designed which can operate at temperatures up to 400°C and at pressure up to 1MPa, calculated at room temperature; with an inter-electrode distance between 100μm and 6.6mm and with an error on the inter-electrode distance measurement of 20μm. In this article, firstly, the results from the experimental investigation on the deviation from Paschen’s law at temperature up to 400°C are presented. The results are then compared with theoretical corrections, and finally a theory to explain the results is proposed and discussed

Characterization and localization of partial-discharge-induced pulses in fission chambers designed for sodium-cooled fast reactors

During the operation of the Superphenix and Phenix reactors, an aberrant electrical signal was detected from the fission chambers used for neutron flux monitoring. This signal, thought to be due to partial electrical discharge (PD) is similar to the signal resulting from neutron interactions, and is generated in fission chambers at temperatures above 400°C. This paper reports work on the characterization and localization of the source of this electrical signal in a High Temperature Fission Chamber (HTFC). The dependence of the shape of the PD or neutron signal on the various experimental parameters (nature and pressure of the chamber filling gas, electrode gap distance, and fission chamber geometry) are described. Next, experiments designed to identify the location within the chambers where the PD are being generated are presented in way to propose changes to the fission chamber in order to reduce or eliminate the PD signal

Réponse en courant des détecteurs silicium aux particules chargées et aux ions lourds

Composition du jury : Mr. Murat BORATAV : Président Mr. Bernard BORDERIE : Directeur de thèse Mr. Roland DAYRAS : Rapporteur Mme. Laurence LAVERGNE : Invitée Mr. Marian PARLOG : Examinateur Mr. Elio ROSATO : Rapporteur Mr. Bernard TAMAIN : ExaminateurThis work consisted in collecting and studying for the first time the shapes of current signals obtained from charged particles or heavy ions produced by silicon detectors. The document is divided into two mean parts. The first consisted in reducing the experimental data obtained with charged particles as well as with heavy ions. These experiments proceeded at the Orsay Tandem and at GANIL using LISE. These two experiments enabled us to create a data base formed of current signals with various shapes and various times of collection. The second part consisted in carrying out a simulation of the current signals obtained from the various ions. To obtain this simulation we propose a new model describing the formation of the signal. We used the data base of the signals obtained in experiments in order to constrain the three parameters of our model. In this model, the charge carriers created are regarded as dipoles and their density is related to the dielectric polarization in the silicon detector. This phenomenon induces an increase in permittivity throughout the range of the incident ion and consequently the electric field between the electrodes of the detector is decreased inside the trace. We coupled with this phenomenon a dissociation and extraction mode of the charge carriers so that they can be moved in the electric field.Ce travail a consisté à collecter puis étudier pour la première fois les formes de signaux de courant issus de détecteurs silicium lors de l'interaction des particules chargées ou des ions lourds avec ces derniers. Ce document est divisée en deux grandes parties. La première consistait à dépouiller les données expérimentales obtenues avec des particules chargées ainsi que des ions lourds. Ces expériences se sont déroulées au Tandem d'Orsay et auprès du GANIL en utilisant la ligne LISE. Ces deux expériences nous ont permis de créer une base de données formée de signaux de courant avec différentes formes et différents temps de collection. La deuxième partie consistait à réaliser une simulation des signaux de courant issus des différents ions. Pour obtenir cette simulation nous avons pu développer un nouveau modèle décrivant la formation du signal. Nous avons utilisé la base de données des signaux obtenus expérimentalement afin de contraindre les trois paramètres de notre modèle. Dans ce modèle, les porteurs de charges créés sont considérés comme des dipôles et ainsi leur densité est reliée à la polarisation diélectrique dans le détecteur silicium. Ce phénomène induit une augmentation de constante diélectrique tout au long de la trace de l'ion incident et par conséquent le champ électrique entre les électrodes du détecteur est diminué à l'intérieur de la trace. Nous avons couplé à ce phénomène un mode de dissociation et d'extraction des porteurs de charges afin qu'ils puissent se mettre en mouvement dans le champ électrique

Réponse en courant des détecteurs silicium aux particules chargées et aux ions lourds

Composition du jury : Mr. Murat BORATAV : Président Mr. Bernard BORDERIE : Directeur de thèse Mr. Roland DAYRAS : Rapporteur Mme. Laurence LAVERGNE : Invitée Mr. Marian PARLOG : Examinateur Mr. Elio ROSATO : Rapporteur Mr. Bernard TAMAIN : ExaminateurThis work consisted in collecting and studying for the first time the shapes of current signals obtained from charged particles or heavy ions produced by silicon detectors. The document is divided into two mean parts. The first consisted in reducing the experimental data obtained with charged particles as well as with heavy ions. These experiments proceeded at the Orsay Tandem and at GANIL using LISE. These two experiments enabled us to create a data base formed of current signals with various shapes and various times of collection. The second part consisted in carrying out a simulation of the current signals obtained from the various ions. To obtain this simulation we propose a new model describing the formation of the signal. We used the data base of the signals obtained in experiments in order to constrain the three parameters of our model. In this model, the charge carriers created are regarded as dipoles and their density is related to the dielectric polarization in the silicon detector. This phenomenon induces an increase in permittivity throughout the range of the incident ion and consequently the electric field between the electrodes of the detector is decreased inside the trace. We coupled with this phenomenon a dissociation and extraction mode of the charge carriers so that they can be moved in the electric field.Ce travail a consisté à collecter puis étudier pour la première fois les formes de signaux de courant issus de détecteurs silicium lors de l'interaction des particules chargées ou des ions lourds avec ces derniers. Ce document est divisée en deux grandes parties. La première consistait à dépouiller les données expérimentales obtenues avec des particules chargées ainsi que des ions lourds. Ces expériences se sont déroulées au Tandem d'Orsay et auprès du GANIL en utilisant la ligne LISE. Ces deux expériences nous ont permis de créer une base de données formée de signaux de courant avec différentes formes et différents temps de collection. La deuxième partie consistait à réaliser une simulation des signaux de courant issus des différents ions. Pour obtenir cette simulation nous avons pu développer un nouveau modèle décrivant la formation du signal. Nous avons utilisé la base de données des signaux obtenus expérimentalement afin de contraindre les trois paramètres de notre modèle. Dans ce modèle, les porteurs de charges créés sont considérés comme des dipôles et ainsi leur densité est reliée à la polarisation diélectrique dans le détecteur silicium. Ce phénomène induit une augmentation de constante diélectrique tout au long de la trace de l'ion incident et par conséquent le champ électrique entre les électrodes du détecteur est diminué à l'intérieur de la trace. Nous avons couplé à ce phénomène un mode de dissociation et d'extraction des porteurs de charges afin qu'ils puissent se mettre en mouvement dans le champ électrique

Réponse en courant des détecteurs silicium aux particules chargées et aux ions lourds

STRASBOURG-Bib.Central Recherche (674822133) / SudocPARIS-BIUSJ-Thèses (751052125) / SudocPARIS-BIUSJ-Physique recherche (751052113) / SudocSudocFranceF

Investigation of fission chamber response in the frame of fuel debris localization measurements at Fukushima Daiichi

International audienceThis work aims at assessing the performance of a 235U enriched fission chamber in order to localize fuel debris, prior to dismantling operations, in a flooded primary containment vessel of a damaged nuclear reactor such as Fukushima Daiichi. Based on both a comprehensive scan of the environment and the detection of neutrons emitted by the melted core, fuel debris can be localized. In this paper, we carry out a simulation study using the MCNP6 code to investigate fission chamber response in the frame of fuel debris localization measurements in a damaged nuclear reactor. The CFUF34 fission chamber (manufactured by PHOTONIS) and the primary containment vessel of Fukushima Daiichi Unit 1 were chosen to conduct this work. Impact of different parameters were investigated with MCNP6, such as: neutron energy, water temperature, fission chamber position (altitude, lateral shift, and rotation), and sensitivity loss due to sediments potentially covering fuel debris. In summary, we show that fuel debris should be sought by their thermal neutron signature at a distance of a few centimeters and that potential rotational movements of the fission chamber up to 60° have a limited impact on signals measured. We also show that sensitivity loss due to sediments potentially covering fuel debris has been evaluated on the order of a factor 10 considering a 30 cm-thick sediment layer. On the other hand, experiments were performed to assess the impact of a strong gamma dose rate on fission chamber measurements. These irradiation trials involved a CFUE32 fission chamber (also manufactured by PHOTONIS) available in our laboratory and three different irradiation means: an X-ray tube, an 192Ir source, and a linear electron accelerator. These experiments enable to draw the conclusion that the fission chamber is not impacted by the gamma dose rate up to 104 Gy h−1, which is in good agreement with specifications provided by the manufacturer (PHOTONIS). In addition, no performance degradation was observed after an integrated gamma dose of 2200 Gy on the fission chamber in a 10 min irradiation. However, when the fission chamber is irradiated by gamma dose rates above 104 Gy h−1 (upper limit of the operating domain specified by PHOTONIS), a significant gamma background is observed. Nevertheless, as the gamma dose rates at Fukushima Daiichi should not exceed 103 Gy h−1, fission chamber measurements performed towards fuel debris localization in the primary containment vessels of the units would not be affected by the severe gamma-ray irradiation