Quantification of plutonium heterogeneity in (U, Pu) mixed oxide fuel using Passive Gamma Scanning

During the fabrication of (U, Pu)O2 mixed oxide (MOX) fuel for the Prototype Fast Breeder Reactor (PFBR), which is being built at Kalppakkam, India, it was necessary to achieve homogeneous distribution of plutonium in UO2 matrix for good thermo mechanical behavior of the fuel in reactor as well as for better solubility of the spent fuel during reprocessing. Since the conventional techniques used for estimating plutonium homogeneity in MOX are destructive in nature, they can be performed only on representative samples. The reliability of these techniques is less in large scale MOX fabrication facilities where MOX blends are prepared in large quantity. Passive Gamma Scanning of the fuel pin is carried out as a quality control check for PuO2 content in MOX fuel pin for PFBR. A new methodology has been developed in analyzing the Passive gamma scans to estimate the heterogeneity of plutonium distribution in MOX fuel pins for PFBR.