Method of inspecting repaired stub tubes in boiling water nuclear reactors.

摘要

An ultrasonic method of inspecting repaired stub tubes in a boiling water reactor. The top and bottom ends of each stub tube (14) are respectively welded to the corresponding control rod drive housing (10) and to the bottom head (12) of the reactor pressure vessel. Under certain conditions, a crack (26) can form in the heat-affected zone of the stub tube adjacent to the upper weld (16), necessitating repair by installing a mechanical seal (20). A probe (24) inserted in the control rod drive housing has transducers (28a, 28b, 28c) which transmit pulsed ultrasonic energy toward a machined surface-air gap interface (30) disposed to reflect the pulse trains generally axially through the stub tube. The radial and azimuthal dimensions of a radial crack in the stub tube are determined in dependence on which pulsed trains are reflected back to the probe by the crack via the interface. <IMAGE>