BLISTER GROWTH IN ZIRCONIUM ALLOYS - EXPERIMENTATION AND MODELING

Hydrogen redistribution in the presence of a cold spot is considered, with hydrogen concentrations above the solid-solubility limit and thus with hydrogen flowing through a hydride-matrix mixture. Fully-hydride d regions (frequently called blisters) grow in the samples, beginning at the cold spot, Under equivalent conditions, the experiment is carri ed out on several Zr-2.5% Nb samples, allowing for the hydrogen migrat ion times to vary from 1x10(5) to 6x10(5) s, so as to construct a blis ter-growth curve. Metallographic examination of the samples is perform ed before and after the imposition of the thermal gradient. A mathemat ical model is then presented, and the corresponding equations are nume rically solved by means of a finite element method, refining the discr etization so as to render approximation errors unimportant. Agreement between model and experiment is shown to be quite good for migration t imes greater than 3x10(5) s. For shorter times, implying small blister s around the cold spot, discrepancies arise between model and experime nt, which are attributed to errors in estimating the local temperature field near the sample surface.