Development of a 3-D Measurement Apparatus for Measuring Cell sizes, Spring and Dimple pitches of Grids for PWR's Spent Fuels

A nuclear fuel bundle burns for about 3 cycles in the core of a reactor in general. During irradiation in the core of a reactor, the fuel rods of a bundle are swelled and cooled down by coolant. At this time, some of the springs and dimples of the grids are deformed, and the surface of the fuel rod could be shinny and damaged as a result, however so far the deformation quantities hove not been measured exactly in country. To measure the deformed quantities such as cell sizes, spring-to-spring pitches, and dimple-to-dimple pitches of various kinds of grids, a remotely controlled 3- dimensional measurement apparatus is required. In this paper, the design requirement as well as conceptual design and characteristics of this apparatus are introduced, and test results are shown after installation in the hot cell at IMEF