The hydriding characteristics of Zircaloy-2(Zry), sponge zirconium (as
a liner on Zry plate), and crystal-bar zirconium exposed to pure H-2
at 0.1 MPa or 7 MPa and 400 degrees C were determined in a thermogravi
metric apparatus. The morphology of the hydrided specimens was also ex
amined by optical microscopy. For all specimen types, the rate of hydr
iding in 7 MPa H-2 was two orders of magnitude greater than in 0.1 MPa
H-2. For Zry, uniform bulk hydriding was revealed by hydride precipit
ates at room temperature and on one occasion, a sunburst hydride. In a
ddition, all specimen types exhibited a hydride surface layer. In a du
plex Zry/sponge-Zr specimen, Zry is more heavily hydrided than the spo
nge Zr layer.