Simulation-based investigation of suitability of thermography and muon flux measurements for non-invasive monitoring of transport and storage containers for spent fuel

The search for a radioactive waste repository in deep geological formations is still ongoing in Germany. Until the availability of a long-term storage spent fuel has to be stored in transport and storage containers which are qualified for the dry intermediate storage of spent fuel assemblies. In Germany, these containers are of the type CASTOR V/19 (PWR fuel assemblies) [1] or CASTOR V/52 (BWR fuel assemblies) which has a maximum permissible operating time of 40 years, at the moment. A prolonged intermediate storage of the spent fuel may exceed this period. The knowledge about the long-term behavior of the spent fuel in these containers is very limited. Therefore, there is a great interest in a non-invasive monitoring long-term of the container inventory. This is in the focus of the collaborative project DCS-MONITOR, which was already introduced in more details e. g. in [2]. The range of possible methods is very limited as it is not possible to open the cask or to insert sensors and on the other hand because of the massive walls of the cask, which hamper any non-intrusive access. Within the project gamma and neutron radiation, muon radiography, thermography, and acoustic spectrometry are investigated. In this paper, muon radiography and thermography are discussed.