Papers by Keyword: Nuclear Fuel Rod

Abstract: The welding which is used to seal the hole on the nuclear fuel rod is performed in a chamber which is filled with high-pressure helium. Experiments were done with different current and distance of tungsten and the end plug. Each current curve and voltage curve was analyzed. The results show that the effect of increasing the welding current or shortening the distance between the tungsten electrode and the end plug on the arc is that arc voltage is smaller and the arc stability is improved. The plan that positioning head is composed of two parts was put forward to control the fuel rod positioning accuracy. By means of properly choosing and controlling the parameters, the quality of welding is certainly improved and the rate of rejection is declined.

Abstract: In order to evaluate the effects of a variation of a supporting springs' shape on the wear behavior of a nuclear fuel rod, sliding wear tests have been performed in room temperature air and water. The objective of the tests is to quantitatively evaluate the relationship between a worn area and a wear volume, and the formation behavior of a worn area with a variation of the slip amplitudes, applied normal loads and supporting spring shapes. The results indicated that the variation behavior of the volume and the wear scar size was influenced by the contact shape between the springs and the fuel rods. Also, it was found to be possible to evaluate a critical ratio (Tc) for each spring shape and test condition when the T was defined as the ratio of an applied normal load (Ln) to a wear scar size (At). Below this Tc, the wear volume was rapidly increased and the Tc was determined by a variation of the At under the same applied normal load condition. This result enables us to evaluate a wear resistant spring shape by using an analysis of a wear scar after wear tests have been completed. Based on the above results, the relationship between At and a worn area (Aw), a wear mechanism and an evaluation method for a wear resistance were discussed.

Abstract: An effort has been made in the present investigation to evaluate the wear resistance of nuclear fuel rods with a variation of the supporting spring shapes and their stiffness by conducting fretting wear tests in room temperature air and water. With increasing slip amplitude, the wear volume and maximum wear depth are increased with increasing slip amplitude. However, these are not linearly increased with increasing spring stiffness. After the wear test, the worn surfaces were observed to investigate the debris behavior and wear mechanism by using an optical microscope (OM). The results indicated that almost all of the wear debris remained between the contacting surfaces and the wear debris layers were well developed in room temperature air. Besides, some of the debris also remained on the worn surface in room temperature water. This result shows that the remaining debris effect on the worn surface was more dominant than the spring stiffness one. So, in order to improve the fretting wear resistance of a nuclear fuel rod, it is necessary to consider the debris behavior between contacting surfaces even though the supporting spring shape was optimized by considering the contact mechanics, material compatibility, etc. From the experimental results, the fretting wear mechanisms and the effect of spring properties were discussed.