Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

For the measurement of sub-channel void distributions and dry-out effects in electrically heated fuel element bundles at the thermal hydraulic test loop KATHY (AREVA NP GmbH, Germany) we have recently developed a high-resolution gamma ray tomograph. This device enables a non-invasive measurement of cross-sectional void fraction profiles through the pressure vessel for fuel element bundles under typical nuclear reaction conditions. The gamma ray tomography system consists of a collimated Cs137 isotopic source and a 320 element detector arc. The average spatial resolution of the system is 3 mm in plane and 8 mm axial. With a special gantry vertical positioning and continuous rotation of the measurement setup is realised. Performing transversal scans takes approximately 25 minutes recording time. To measure void fraction calibration measurements have been recorded at zero and one hundred percent void fraction respectively. Image reconstruction was performed with standard filtered back projection algorithms.