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[en] Fracture stress data for the chemical vapor deposition (CVD) SiC coatings of tri-isotropic (TRISO) carbon/silicon carbide coated fuel particles were obtained using a newly developed testing and evaluation method, and their relationship with microstructure investigated. A crush testing technique using a blanket foil at load-transferring contact has been developed for hemispherical shell SiC specimens based on finite element (FE) analysis results. Mean fracture stress varied with test material in the range of 330-650 MPa, and was connected to the combined characteristics of inner surface roughness and porosity.
[en] The invention relates to a transfer device, in particular for transferring small particles, comprising a helical channel made in the tube inner surface, a device for causing the tube to rotate about its longitudinal axis, a rotating joint adapted to close one of the tube extremities, a device for inserting a substance in the form of granules or of fluid particles into said tube through said joint, and a device for collecting and discharging said substance at the tube opposite end. This can applied to the transfer of small spherical particles e.g. of fuel
[fr]L'invention concerne un transporteur, notamment de petites particules. Le transporteur comporte un canal helicoidal menage dans la surface interne du tube, un dispositif pour faire tourner le tube autour de son axe longitudinal, un joint rotatif fermant une extremite du tube, un dispositif pour introduire une matiere sous la forme de granules ou particules fluides dans le tube a travers le joint, et un dispositif pour recueillir et decharger la matiere a l'autre extremite du tube. Ceci est applicable au transport de petites particules spheriques, par exemple d'un combustible nucleaire
[en] The Advanced Gas Reactor (AGR) Fuel Development and Qualification Program has executed a series of experiments to test and qualify tristructural isotropic (TRISO) particle fuels for use in high-temperature gas-cooled reactors. The most recent irradiation experiments, AGR-5/6/7, are testing fuel that was fabricated in near production-scale equipment. There are three important defect fractions that must be characterized, using a deconsolidation-leach-burn-leach (DLBL) method, to better predict and understand fuel performance during irradiation. These are the dispersed uranium fraction (DUF), exposed kernel fraction (EKF), and silicon carbide defect fraction (SDF). The DLBL characterization data from analyses of the four compact batches, fabricated and characterized by the BWX Technologies Nuclear Operations Group (BWXT-NOG), showed unexpectedly higher values for all three defect fractions relative to the parent TRISO particle defect fractions. The DUF and SDF should not have changed significantly during compact fabrication and the apparent increase in the EKF, a metric for particle damage, was higher than anticipated for the compacts with 40% volumetric packing fraction (PF). Analytical results showed no net increase in the EKF for the 25% PF compacts. Compacts from one compact batch of each packing fraction were sent to Oak Ridge National Laboratory (ORNL), along with uncompacted tristructural isotropic (TRISO) particles, overcoated to a thickness targeting a 40% PF, for confirmatory analyses of the defect fractions and determination of the source(s) of damage. The ORNL results did not confirm the BWXT-NOG results for either the DUF or the SDF; the ORNL results showed no significant change in these defect fractions relative to the parent TRISO particle lot. The ORNL results did, however, confirm that a large increase in the exposed kernel fraction was found in the 40% PF compacts and that the 25% PF compacts sustained little if any damage. Data suggest that a large majority of the mechanical damage to the TRISO particles occurred in the overcoater when targeting the 40% PF. The analytical laboratories at both BWXT-NOG and ORNL had inconsistent outcomes on analyses of individual batches. Although the ORNL data is more consistent with the parent TRISO lot and expectations, the data set is too limited in size to justifiably reject suspect data from either laboratory at this time. It is recommended that an additional analysis be done to provide sufficient data for estimating the true defect fractions for interpreting the radionuclide release data during the AGR-5/6/7 irradiation experiments.
[en] The fuel body of a fuel element consists of fuel particles coated with pyrolytic carbon arranged between walls constructed as screens. The screens are formed as cones, double cones or as corrugated pipes and move between the pipe walls of the cylindrical fuel element from one side to the other and back. The particles are held in their position by graphite-felt, graphite fabric or felt or fabric made of SiO2. This stable geometric configuration guarantees that during operation changes of the power distribution in the reactor and reactivity jumps can be avoided. In research reactors even the emergency cooling becomes easier to be carried out. (orig.)
[de]Bei dem BE ist der Brennstoffkoerper aus mit pyrolytischem Kohlenstoff beschichteten Partikeln zwischen als Siebe ausgebildeten Wandungen angeordnet. Die Siebe verlaufen kegel-, doppelkegel- oder wellrohrfoermig zwischen den Rohrwaenden des hohlzylinderfoermigen BE hin und her. Die Partikel werden ausserdem durch die Einlagerung von Graphitfilz, Graphitgewebe bzw. Gewebe und Filz aus SiO2 in unveraenderlicher Lage gehalten. Diese stabile geometrische Konfiguration gewaehrleistet, dass Aenderungen der Leistungsverteilung im Reaktor waehrend des Betriebs sowie Reaktivitaetsspruenge vermieden werden. Bei Forschungsreaktoren laesst sich sogar die Notkuehlung einfacher durchfuehren. (orig.)
[en] This paper is concerned with a novel fuel concept based on a coated-particle-fuel (CPF) for a high-performance and ultra-safe research design. Unlike the conventional U3Si2-dispersed fuel plate, small CPFs are randomly embedded in the Al matrix. A CPF is composed of two components: a central fuel kernel and a thin buffer layer. To optimize the U loading, several type of fuel: UO2, UC and UN are being studied to achieve comparable U densities to U3Si2 or UMo based fuel. A 20MWth research reactor is considered to investigate the potential and characteristics of the new fuel concept in comparison with the conventional plate fuels. Neutronic analysis is done by using continuous energy Monte Carlo code Serpent. In this preliminary study, we found that by using CPF, the fuel Doppler effect can be considerably enhanced, thus increasing the inherent safety of research reactors. In addition, it is clearly shown that the U loading in the core cna be higher or comparable to that of the existing fuels. It is considered that the CPF-based plate fuel concept provides a new way to design an ultra-safe and high-performance research reactor