Visual inspection of inner surfaces of nuclear power plant primary circuit components as practised by the CEZ corporation

The differences are discussed between the draft Czechoslovak regulations for the visual inspection of primary circuit components at nuclear power plants and the corresponding DIN standard. In both documents, visual inspections are classed into direct and indirect ones. The Czechoslovak regulations divide the inspections additionally into three types with respect to the state of the surface, type of component and location of the latter. As to the sensitivity of the visual inspection method, the Czechoslovak draft regulations define the sensitivity as determined by the resolving power for a given angle of viewing and illumination: seeing a black line 0.8 mm broad on an 18% neutral grey card located on the surface inspected or in conditions approaching those of the site inspected. In contrast to the Czechoslovak draft document, the DIN standard lays down technical requirements on periscopes, endoscopes, cameras, manipulators, etc. (Z.M.)