No abstract available

[en] An automated ultrasonic flaw detection system was developed for thin-walled and short tubes such as Zircaloy-4 tubes used for cladding heavy-water reactor fuel. The system was based on the two channels immersion pulse-echo technique using 14 MHz shear wave and the specially developed helical scanning technique, in which the tube to be tested is only rotated and the small water tank with spherical focus ultrasonic transducers is translated along the tube length. The optimum angle of incidence of ultrasonic beam was 26 degrees, at which the inside and outside surface defects with the same size and direction could be detected with the same sensitivity. The maximum permissible defects in the Zircaloy-4 tubes,i.e., the longitudinal and circumferential v notches with the length of 0.76 mm and 0.38 mm, respectively and the depth of 0.04 mm on the inside and outside surface, could be easily detected by the system with the inspection speed of about 1 m/min and the very excellent reproducibility. The ratio of signal to noise was greater than 20 dB for the longitudinal defects and 12 dB for the circumferential defects. (Author)

[en] A method in which dimensional measurements are used for ovality and bow determination. This provides a simple and accurate way to correlate the diameter measurements. (authors)

[en] A series of experimental irradiations has been undertaken at CRNL to measure directly the in-reactor deformation of fuel elements while they are operating at power. Power histories have been chosen to allow investigation of power, time at power and burnup on pellet-clad interaction for element linear powers to 60kW/m. Results are presented which indicate that irradiation of a fresh fuel element at high power is effective in minimizing clad hoop stresses during subsequent ramps or cycles to that power. The effectiveness of this preconditioning appears to be due primarily to fuel densification rather than stress relaxation in the clad. (auth)

[en] This paper investigated the different sizes and geometric shapes of ceramic uranium dioxide pellets which have influnce on pellet-cladding interaction. The improved pellet design and several kinds of new pellets are also introduced

[en] A process for providing an aperture in a wall with a protective layer (e.g. a wall of a container such as fuel cladding of a nuclear fuel pin) includes the step of disrupting the protective layer (e.g. by scratching with a probe) at a selected location so as to facilitate dissolution of the wall at the location when contacted with a solvent in order to produce an aperture in the wall. The fuel can then be removed from the fuel pin by means of a solvent through the aperture which has been formed. (author)

[en] This paper views the ridging as a result of axial pellet-clad mechanical interaction. In a fuel rod, the pellet stack undergoes axial compression as firm locking between fuel and clad develops at a certain power level. As the power increases beyond this level, the axial constraint increases, the pellet fragments are pressed into the hourglass shape, and ridging of the cladding results. (orig./HP)

[en] A series of experiments is described which studied the penetration of structures by molten UO₂. The UO₂ was produced by ignition of a U/MoO₃ thermite which yielded a molten mixture of UO₂ and Mo at a temperature of about 3600K. This mixture was injected into pin arrays and tubes with driving pressures ranging from zero (a gravity pour) to 2MPa. (author)

[en] To determine the tensile properties of irradiated fuel cladding in a hot cell, a simple test was developed at the Oak Ridge National Laboratory (ORNL) and is described fully in US Patent Application 20060070455, ''Expanded plug method for developing circumferential mechanical properties of tubular materials.'' This method is designed for testing fuel rod cladding ductility in a hot cell using an expandable plug to stretch a small ring of irradiated cladding material. The specimen strain is determined using the measured diametrical expansion of the ring. This method removes many complexities associated with specimen preparation and testing. The advantages are the simplicity of measuring the test component assembly in the hot cell and the direct measurement of the specimen's strain. It was also found that cladding strength could be determined from the test results.

No abstract available