An amphibious inspection robot system (hereafter AIROS) is being developed to visually inspect the in-containmentrefueling storage water tank (hereafter IRWST) strainer in APR1400 instead of a human diver. Four IRWST strainers arelocated in the IRWST, which is filled with boric acid water. Each strainer has 108 sub-assembly strainer fin modules thatshould be inspected with the VT-3 method according to Reg. guide 1.82 and the operation manual. AIROS has 6 thrusters forsubmarine voyage and 4 legs for walking on the top of the strainer. An inverse kinematic algorithm was implemented in therobot controller for exact walking on the top of the IRWST strainer. The IRWST strainer has several top cross braces that areextruded on the top of the strainer, which can be obstacles of walking on the strainer, to maintain the frame of the strainer. Therefore, a robot leg should arrive at the position beside the top cross brace. For this reason, we used an image processingtechnique to find the top cross brace in the sole camera image. The sole camera image is processed to find the existence of thetop cross brace using the cross edge detection algorithm in real time. A 5-DOF robot arm that has multiple camera modules forsimultaneous inspection of both sides can penetrate narrow gaps. For intuitive presentation of inspection results and formanagement of inspection data, inspection images are stored in the control PC with camera angles and positions to synthesizeand merge the images. The synthesized images are then mapped in a 3D CAD model of the IRWST strainer with the locationinformation. An IRWST strainer mock-up was fabricated to teach the robot arm scanning and gaiting. It is important to arriveat the designated position for inserting the robot arm into all of the gaps. Exact position control without anchor under the wateris not easy. Therefore, we designed the multi leg robot for the role of anchoring and positioning. Quadruped robot design ofinstalling sole cameras was a new approach for the exact and stable position control on the IRWST strainer, unlike atraditional robot for underwater facility inspection. The developed robot will be practically used to enhance the efficiency andreliability of the inspection of nuclear power plant components.