Avaliação da formação de hidretos metálicos em ligas de zircônio

Abstract

Zirconium alloys have greater applicability in the nuclear industry are used in the manufacture of tubes that make up a metal structure , called the fuel element , and form the core of nuclear reactors . Such tubes are used in the coating of ceramic pellets of enriched uranium dioxide and precipitation of hydrides can undergo in operating conditions . This effect is detrimental to the aforementioned alloys , with a view to reducing the ductility depending on the morphology of hydrides . The morphology of hydrides and their respective susceptibility to formation were evaluated in samples of commercial zirconium alloys Zircaloy - 4 ®, ZIRLO ® and M5 ™ . The samples were hydrogenated in an autoclave under the conditions of pressure and temperature of a nuclear reactor . Later microstructural analysis and verification of alloy metal hydrides formed morphology , were made by optical microscopy and scanning electron as well as the technique of X-ray diffraction was used to identify the presence of hydrides. Circumferential hydrides were formed, by hydrogenation condition that only the radial hydrides and M5 ™ alloy, which are undesirable to be more deleterious to mechanical properties, the alloy is formed Zirlo™ M5®, and for more severe hydrogenation conditions. For both types of hydrogenation was not observed in the presence of hydrides Zircaloy-4 ®