State monitoring of transport and storage containers for spent fuel
Sub-Project: Thermographic and radiographic measurement methods
The the continuing search for a long-term storage for highly-active nuclear waste in Germany requires a prolonged intermediate storage of spent fuel in dry storage casks at the power plant sites. For the moment it is not sufficiently clear if there may be a loss of integrity of fuel rods during such long times, e.g. due to rising pressure from gaseous product of nuclear decay. An extrapolative modelling of the radiochemical and thermomechanical material behavior is challenging regarding a final evaluation. Therefore, it is of public interest to find and potentially implement methods which can provide information about the condition of the storage container inventory.
The overall aim of the project is the evaluation of different physical measurement principles and methods for non-invasive monitoring of the condition of the container inventory in case of prolonged intermediate storage. With that options should be determined to identify changes of the spent fuel and inner container structure over long periods without opening the container. A suitable method or a combination of methods would be a significant contribution regarding the long-term safety of intermediate stored highly radioactive waste. Such a method would provide evidences about the transport and conditioning ability of the waste before transfer to the repository.
Methods and results
First it is investigated whether the gamma radiation, neutron radiation or heat from the spent fuel can be used to diagnose long-term changes in the nuclear inventory of dry storage casks. For the case of radiation Monte-Carlo simulations are used to calculate external radiation fields from given internal source term distributions. For thermal measurements such simulations are carried out with combined FEM and CFD simulations. In both cases simulations are based on realistic cask geometries, loading patterns and storage times. Moreover, the potential of using cosmic myons for radiographic investigation of the cask inventory are being investigated. The latter is done as well with Monte-Carlo simulations. Last not least we investigate on the use of passive and active acoustic spectroscopy methods, e.g. to detect burst noise and changes in the vibration spectra of fuel assemblies. Basing on these investigations, condition diagnosis methods for multimodal data sets will be developed.
This project is funded by the German Federal Ministry of Economic Affairs and Energy under the funding code 1501518A.
Hochschule Zittau/Görlitz, Institut für Prozeßtechnik, Prozeßautomatisierung und Meßtechnik(ipm.hszg.de/institut.html)