Nuclear power reactors, in common with other types of thermal power generators, require a vast quantity of pipe and tubing. Thermal energy is generated in one locality and must be transferred to some fluid by means of heat exchangers and radiators, and thence transported through pipes to another location for conversion into mechanical energy. Most of the pipe and tubing is used in critical regions, with both the inside and outside of the tube wall subjected to severe corrosive environments. Temperature gradients set up thermal stresses which may aid in the propagation of small defects or enhance the corrosion rate. Any leak would be extremely hazardous both from a personnel standpoint and from the viewpoint of further damage to surrounding areas within the system.An added difficulty is the fact that once in operation, certain areas will no longer be accessible for repairs; hence soundness must be guaranteed from the start. Because of the great footage of tubular shapes and the quality required, special inspection techniques are indicated.