Micro gamma scanning on the high burnup PWR fuel samples

The ratio of Cs-137 and Cs-134 provides important clues about the nuclear fuel burnup. However, Cesium has a tendency to be released from the fuel pellet with increasing burnup and the distribution of Cesium has a bathtub shape along the radial direction of a fuel pellet due to the self shielding effect in neutron spectrum. The distribution of the radioactive nuclides affects the gamma spectra measuring in the lateral face of a spent fuel rod. That should be corrected in estimating the fuel burnup. This study aims to measure the distribution of nuclides as a preceding work of correcting the burnup estimation for Cs distribution. In order to measure the radial distribution of Cs-137 and Cs-134, disk type samples were prepared from the PWR spent fuel rods, and the micro gamma scanning was performed on the samples