To answer your question, a lot more information is needed. A comprehensive inspection program depends a lot on the physical characteristics and operational history of your plant.
I assume that this is a probably a carbon-steel steam piping system feeding a steam turbine or similar process component.
For a steam system of this type, both Ultrasonic testing and Radiographic testing are commonly used. In the USA, API-572(?) guideline has been used to set up inspection programs.
My opinion only....
MJC