13 research outputs found

    LIQUID LEAD-BISMUTH EUTECTIC AS A COOLANT IN GENERATION IV NUCLEAR REACTORS AND IN HIGH TEMPERATURE SOLAR CONCENTRATOR APPLICATIONS: CHARACTERISTICS, CHALLENGES, ISSUES

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    Heavy liquid metals have found a wide range of application in energy conversion systems, due to their beneficial thermal properties, especially their low melting points and their capability of operating at higher temperatures without boiling. In addition, the neutronic properties of various liquid metals make them attractive for fusion as well as in Generation IV nuclear reactors. Lately, concentrated solar power (CSP) systems have developed an interest in this technology, calling for temperatures up to 800 oC. The main challenge in realizing engineering scale units is to find proper structural materials that can withstand the corrosion and provide mechanical strength at operation conditions. Lead-Bismuth Eutectic (LBE) is one of the main candidate coolants for liquid metal cooled reactors and solar thermal power applications due to its physical properties such as good thermal conduction, low thermal expansion and melting point, non-violent reactivity to water and low neutron absorption. However, the key limiting factor for LBE usage is the fact of its high corrosiveness to steels and other structural materials. In this work, the results of our systematic materials study in liquid LBE and its alternatives are presented. Various potential structural materials were exposed to LBE, Roseā€™s metal (Pb-Bi-Sn) and Pb-Bi-Zn eutectic, in static corrosion tests. Post corrosion characterization was conducted by micro-structural analysis (SEM/EDS, X-ray diffraction, Raman spectroscopy) and preferential corrosion mechanisms were evaluated.Heavy liquid metals have found a wide range of application in energy conversion systems, due to their beneficial thermal properties, especially their low melting points and their capability of operating at higher temperatures without boiling. In addition, the neutronic properties of various liquid metals make them attractive for fusion as well as in Generation IV nuclear reactors. Lately, concentrated solar power (CSP) systems have developed an interest in this technology, calling for temperatures up to 800 oC. The main challenge in realizing engineering scale units is to find proper structural materials that can withstand the corrosion and provide mechanical strength at operation conditions. Lead-Bismuth Eutectic (LBE) is one of the main candidate coolants for liquid metal cooled reactors and solar thermal power applications due to its physical properties such as good thermal conduction, low thermal expansion and melting point, non-violent reactivity to water and low neutron absorption. However, the key limiting factor for LBE usage is the fact of its high corrosiveness to steels and other structural materials. In this work, the results of our systematic materials study in liquid LBE and its alternatives are presented. Various potential structural materials were exposed to LBE, Roseā€™s metal (Pb-Bi-Sn) and Pb-Bi-Zn eutectic, in static corrosion tests. Post corrosion characterization was conducted by micro-structural analysis (SEM/EDS, X-ray diffraction, Raman spectroscopy) and preferential corrosion mechanisms were evaluated

    A clinical evaluation of the Zygoma fixture: One year of follow-up at 16 clinics

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    Purpose. To evaluate treatment outcome with Zygoma fixtures (Nobel Biocare, Goteborg, Sweden) with regard to fixture survival, patient satisfaction, and function of prosthesis replacement. Materials and Methods: The treatment outcome of 76 patients treated with 145 Zygoma fixtures at 16 centers was evaluated. Patient's and dentist's evaluations of the functional and aesthetic outcome of the treatment were assessed at delivery of prosthesis and at the 1-year follow-up visit. At the 1-year follow-up visit, the status of the peri-implant mucosa around the abutments and the amount of plaque were registered. Results: Sixty-six of the 76 patients, with 124 Zygoma fixtures supporting the prosthetic restorations, were evaluated at the 1-year follow-up. The overall survival rate for the Zygoma fixtures was 97.9% after 1-year of follow-up. Eighty percent of the patients were fully satisfied with both aesthetic and functional outcome at the time of prosthetic insertion and at the 1-year follow-up. All reported data from the dentists, with the exception of one restoration with several abutment screw loosenings, scored from acceptable to excellent for the aesthetic and functional outcome of the treatment. The status of peri-implant mucosa was recorded as normal in approximately 60% of the sites. Plaque, when present, was more often detected on the palatal surfaces compared with the buccal surfaces. Conclusion: This 1-year follow-up of Zygoma fixtures has shown good results with an acceptable number of minor complications and a majority of satisfied patients. (C) 2004 American Association of Oral and Maxillofacial Surgeons

    Clinical evaluation of the zygoma implant: 3-year follow-up at 16 clinics

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    Purpose: The purpose of this clinical investigation was to evaluate the treatment outcome with zygoma implants with regard to implant survival, patient satisfaction, and function of prosthesis replacement after 3 years. Patients and Methods: The treatment outcome of 76 patients treated with 145 zygoma fixtures at 16 centers was evaluated with regard to implant survival. Status of peri-implant mucosa and amount of plaque were registered annually. Patients' and dentists' evaluations of the functional and esthetic outcome of the treatment were assessed at delivery of prosthesis and thereafter at each follow-up visit. Results: Sixty of 76 patients were followed for 3 years after prosthetic delivery. Five of 145 placed zygoma implants failed during the course of the study resulting in an overall implant survival rate of 96.3%. At the 3-year follow-up, 75% of the implants sites were registered with normal peri-implant mucosa and 68% with no visible plaque. The patients were fully satisfied with the esthetic and functional outcome of the treatment in 86% and 71%, respectively, at the 3-year follow-up visit. All reported data from dentists scored from acceptable to excellent. Conclusion: The multicenter study showed a high predictability of the zygoma implant-supported rehabilitation. (c) 2007 American Association of Oral and Maxillofacial Surgeons
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