Unattended System for Monitoring Storage Cask Movement at the Thorp Facility in the United Kingdom

An unattended system for monitoring movements of containers with spent-fuel elements at the THORP reprocessing facility has been installed and tested. The underwater system is located in the transfer channel between the cask unloading pool and the main storage pool. The equipment is being used and evaluated by the EURATOM inspectorate. Gamma detectors are used to determine when racks with multi-element bottles (MEB), containing lightwater reactor assemblies, or skips, containing advanced gas reactor elements, are moved through the channel in either direction. Detection of spent-fuel assemblies will trigger a video system to record the event. The video images are annotated with pertinent information including the date and time of the movement and an indication of the direction of the movement (either into or out of the storage pool). Data for each event are also stored and can be printed on request at a later time. The system was jointly designed and installed by EURATOM, British Nuclear Fuels, plc(BNFL), Los Alamos National Laboratory (LANL), and Sandia National Laboratories (SNL). This paper provides the details of the system design, operation and field evaluation.