Abstract: An apparatus for inspection of a reactor vessel includes trolley supporting an axillay extending support mast and extension mast. The support mast has a tilting device to adjust the angle between the support mast and vessel wall to allow the extension mast to be accessible to lower portions of the reactor vessel. The lower part of the extension mast is connected to a rack having a horizontal trolley capable of tangential movement relative to the reactor vessel wall. The horizontal trolley also is connected to a probe position trolley enabling a probe holder to move tangentially relative to the horizontal trolley. The apparatus enables the probes to move radially and axially for greater access to positions of the reactor vessel wall.