U Tube Bundle Inspection

There are flexible inspection scopes that are commercially available that you can rent, try and buy. Your choice is either a bore scope with an articulated arm or a flexible fiber optics inspection scope with an attached video camera and a light source at the other end..

the borescope tools can not measure the thickness, I need tools that can measure the thickness at bended section of the U-Bundle

For the 90° bend, you’d normally need a flexible or articulated inspection probe designed to negotiate the U-bend. Standard straight-tube ECT/IRIS probes generally won’t cover the curved section.
There are specialized U-tube eddy-current probes and flexible borescopes, depending on the tube diameter and material. The tube ID and bend radius are important when selecting the right tool.