To inspect the defects on the screw hole surfaces of nuclear reactor pressure vessel in
nuclear power station, an automatic moving table was designed to carry sophisticated inspecting
devices. Its precise positioningwas successfully realized by determining the positionsof the screw holes
in the flange of the pressure vesselwith two optical sensors. Its positioning precision is 0. 15 mm, in
accordancewith the design requiremen,t and themoving table has been put into operationwith precise
and stable performances.