[en] A fuel motion detection system based on coded aperture imaging has been developed for the Annular Core Research Reactor. Its configuration evolved after investigations were carried out to determine the required system capabilities. The reactor environment, developments in the theory of coded apertures for nuclear radiations and compatibility with prototypical geometries were considered. The system was fabricated and inserted into the ACRR where it has recorded the fuel motion from a single pin subjected to loss of flow accident conditions. In addition, computer simulations have shown that in the reactor environment and for fast data acquisition, coded imaging, particularly with uniformly redundant arrays, offers significant advantages over pinhole camera geometries. The extension of this technique toward imaging of 37-pin bundles and imaging with fast neutrons is also being investigated