Mechanical Behavior at High Temperatures of Highly Oxygen- or Hydrogen-Enriched α and Prior-β Phases of Zirconium Alloys

Abstract

Mechanical behavior at high temperature of highly oxygen-or hydrogen-enriched α and (prior-) β phases of zirconium alloys 5 M5 is a registered trademark of AREVA NP in the USA or other countries 2

Phase transformations during cooling from the βZr phase temperature domain in several hydrogen-enriched zirconium alloys studied by in situ and ex situ neutron diffraction

“…In order to investigate the effect of hydrogen, the samples were homogeneously charged with hydrogen at approximately 320, 1100-1500, and 3300 wppm. Hydrogen charging was performed in an argon/hydrogen gas mixture at 400°C to obtain ~300 wppm of hydrogen and, as already done in [13], at 800°C to reach 1100-1500 wppm or 3300 wppm of hydrogen. The samples were then cooled down to RT at a few °C/min.…”

“…During cooling, the β Zr phase transforms back into the α Zr phase and forms the so-called prior-β Zr structure [11]. The mechanical strength of the cladding during and after cooling mainly results from the mechanical behavior of the residual prior-β Zr layer [12] [13]. The mechanical behavior of the (prior-)β Zr structure principally depends on its oxygen and hydrogen contents and on the structural and metallurgical evolutions that take place during cooling from HT [8][10] [14].…”

“…Data for materials with higher hydrogen contents and cooled from HT are scarce and often limited to room temperature (RT) [16] [17]. Recent results have nonetheless shown that the mechanical behavior of the (prior-)β Zr material is affected by high hydrogen contents up to approximately 3000 wppm in ways that strongly depend on temperature between 20°C and 700°C [13]. In order to interpret such results, it is necessary to have a good knowledge of the microstructural and microchemical evolutions that take place during cooling from HT.…”

Combined effects of temperature and of high hydrogen and oxygen contents on the mechanical behavior of a zirconium alloy upon cooling from the βZr phase temperature range

“…In accordance with the safety requirements, it is essential that the cladding retains some mechanical resistance or ductility to ensure its integrity and a coolable core geometry during and after a LOCA transient. At the end of a LOCA transient, the cladding's mechanical strength and ductility mainly result from the mechanical properties of the residual prior-βZr phase layer [6,[10][11][12]. It was found that the mechanical behavior of this layer is strongly influenced by its oxygen and hydrogen contents [6,11,13,14].…”

“…At the end of a LOCA transient, the cladding's mechanical strength and ductility mainly result from the mechanical properties of the residual prior-βZr phase layer [6,[10][11][12]. It was found that the mechanical behavior of this layer is strongly influenced by its oxygen and hydrogen contents [6,11,13,14].…”