Nuclear reactor components are known to degrade as reactors age. The reactor pressure vessel and the reactor internals are subjected to the highest radiation fields and thus, age faster. Some boiling water reactors are experiencing extensive cracking of the core shroud and some pressurized water reactors are experiencing a reduction in their fracture toughness. This paper provides background information on reactor pressure vessel materials, fabrication, and construction practices. It identifies some of the challenges that are associated with the nondestructive measurement of changes in material properties associated with these components. The inspection environment, surface conditions and designs are also discussed.