Each antenna array emits microwaves, which pass through the insulating material without reflection.
When there is water or corrosion residue in the insulation, the microwaves are reflected and bounce back to the antenna array.
Time of flight determines the distance from the antenna array to the area of the ingress or corrosion, and the level of amplitude indicates the extent of the ingress or presence of corroded material.
The pipe with insulation and outer metal sheet acts as a signal conductor similar to a coaxial cable and is ideal for carrying high frequency microwaves.
A reflector is used to optimize the sensitivity of the CUI system.