Ultrasonic probes for inspection of reactor pressure vessel bottom head and weld buildup thereon

摘要

An improved method for repair of incore-instrumentation- housing and related defects in a nuclear reactor system involves three stages, each with ultrasonically assisted inspections. In the first stage, a defective incore housing is removed and the exposed area and aperture at the former location of the incore housing is ultrasonically inspected using an ultrasonic probe with a tiltable disk-shaped head that self- conforms to the local contour of the reactor vessel bottom. In the second stage, a weld buildup is formed. The reactor is then sealed and the weld buildup is machined to define an aperture therethrough. The weld buildup is then ultrasonically inspected with a second probe with a centering member that is stationary as the probe body is moved vertically relative to it. In the third stage, a J-prep is formed. A new incore housing is inserted through the weld buildup aperture. The new incore housing is welded at the J-prep. The J-weld is ultrasonically inspected using a third ultrasonic probe. The new incore housing is then connected to the incore guide tube with shrink couplings, and reactor activity can be restored.