Metallography of High Burnup PHWR Fuel

Abstract

Detailed metallographic examination and B-Y autoradiography have been carried out on the samples taken from the fuel pins of two high burn-up bundles. The observed microstructural features indicate that the main mechanism of fission gas release in the fuel has been formation of interconnected grain boundary fission gas bubbles at the hot central region of the fuel. Quantitative information generated has shown that these bubbles grow, interconnect and finally get released through the grain boundary channels.