Non-invasive multimodal monitoring of transport and storage containers for spent fuel

Until the availability of a final nuclear waste disposal in deep geological formations, spent fuel has to be safely stored for several decades in transport and storage containers, which are qualified for dry intermediate storage of spent fuel assemblies. There is a great interest in monitoring those containers in order to get aware of any changes occurring to the inventory. Getting information from the interior of the massive steel containers with 48 cm thick walls is very difficult. For this reason, we assess the possibility of detecting changes to the spent nuclear fuel distribution in the containers by combining different non-invasive measurement principles. These include thermography of the outer container walls, analysis of the gamma and neutron radiation field from the spent fuel, imaging of the inventory using transmission and scattering of cosmic muons, acoustic spectrometry including vibration analysis and sound emission analysis for detecting cracks of the fuel rods. For some of these techniques inverse problems must be solved in order to localize the detected changes. For the moment, we employ distinct numerical simulation approaches to assess the potential of the proposed methods. Moreover, we perform comparative experiments at downscaled test facilities. Eventually, we shall develop a technically applicable and reliable monitoring concept.