Fuel Assembly Height Measurements at the Nuclear Power Plant Unit Active Zone

The article studies the system of fuel assembly (FA) height measurement by single CCD camera. The algorithm of FA height measurement involves camera moving around the circle of radius 3 m and forming the images from six locations. Suspension height of the camera provides simultaneous observation of the cell with 7 fuel assemblies. Optical axis of camera in each location passes through the gravity center of the central FA upper surface. The camera mathematical model and developed software allows to register discrete pixel coordinates, that display the gravity centers of FA heads upper surfaces. The paper gives the detailed analysis for three stereo pairs of images, got as combinations of measurements from four camera locations: two adjacent locations, two locations in one from each other, and two opposite locations. Algorithm analysis gives minimum height measuring error and reasonable camera locations selection for obtaining most precise measurement results. The paper proves possibility of restriction to measurements from pairs of opposite camera locations to reach the maximum FA height measurement precision.