Reachability Study of Inspection Probes in Helical Tubes

The small diameter and helical geometry of steam generator tubes in High Temperature Gas Cooled Reactor (HTGR) results in problem of reachability of probe for in-service inspection, whatever the probes of ultrasonic, eddy current inspecting or fiber scope. The special designed probe is a must for probe geometry design. In this paper, we modelled the pass-through geometry and interference of probes and helical tube. Three kinds of probes geometries are explored with simulation. Several typical geometry parameters are recommended for probe geometry design. Deviation is analyzed considering the tube diameter and probes manufacture error. Finally, pass-through experiment of probe phantom and helical tube proves the reachability simulation in this paper is well suited to the design. Under the same size, the ellipsoidal shape has the best reachability, and the double-sided hemispherical shape and cylinder shape are not so good. (author)