3D Laser Inspection of Fuel Assembly Grid Spacers for Nuclear Reactors Based on Diffraction Optical Elements

Abstract

Ensuring the safety and high operation reliability of nuclear reactors takes 100% inspection of geometrical parameters of fuel assembly elements, which includes the grid spacers performed as cellular structure with fuel elements. The required grid spacers geometry of assembly in the transverse and longitudinal cross sections is extremely important for maintaining the necessary heat regime. New approach for grid spacers inspection using the diffraction optical elements is investigated. Diffraction optical elements (DOEs) are used for forming the structural illumination on the surface of grid. For inspection of all produced grids nomenclature some DOEs forming different field configurations have been used. The special objective has been developed for forming the inner surface cell image. The problems of diffraction elements synthesis, projecting optics calculation, adjusting methods as well as calibration of experimental measuring system are considered. The algorithms for image processing for different constructive elements of grids (cell, channel hole, outer grid spacer rim) and the experimental results have been shown. The position deviation measurement error of cell centers at the laboratory tests was ±0,007 mm.