  The interaction of hydrogen and metals continues to be industrially relevant
and is a critical part of creating and supporting a safety case for nuclear
reactor operation. In the present work, we explore hydrogen storage and hydride
formation in a zirconium alloy. We characterise the structure and interfaces of
fine scale hydrides using scanning transmission electron microscopy (STEM)
including energy dispersive spectroscopy (EDS/EDX), electron energy loss
spectroscopy (EELS), and high-resolution STEM. Chemical characterisation is
supported further with atom probe tomography (APT). Samples were prepared with
cryo-focussed ion beam machining (cryo-FIB) and contain hydrides in {\alpha}-Zr
matrix and hydrides associated with one FeCrZr secondary phase particle (SPP).
Major findings include characterisation of different interface planes based
upon the size of the hydrides and chemical redistribution of solute ahead of
the hydride-metal interface. We also find significant (up to 6 at%) hydrogen
retained in solution within the zirconium matrix and show a hydride with only
17 at% hydrogen, which is well below that of a {\xi}-phase stoichiometry
suggesting it is an embryonic hydride. These findings help us understand the
distribution of hydrogen and the nanoscale morphology of hydrides, which may
influence the lifetime of zirconium-based nuclear fuel cladding.
