Estimation of Plutonium Heterogeneity in Thoria–Plutonia Fuels

Abstract

Plutonium bearing mixed oxide (MOX) fuels requires to be characterized for plutonium homogeneity as it is a crucial characteristic for fuel performance. Conventional chemical analytical methods for characterization of homogeneity are difficult to be carried out on MOX fuels with thoria matrix due to poor solubility. Radiation imaging is an effective technique to monitor the distribution of plutonium in thoria matrix. Alpha autoradiography is an imaging technique which involves registration of alpha tracks using alpha-sensitive films known as solid-state nuclear track detectors (SSNTD). Manual evaluation of microscopic images from alpha autoradiographs is difficult to carry out where highly radioactive materials such as plutonium are involved due to large number of registered tracks. A method based on image analysis of alpha autoradiographs was explored. The method was applied on alpha autoradiographs of fuel samples with the same composition but having different levels of Pu homogeneity. Samples fabricated through two different routes, viz. the conventional powder–pellet (POP) route and coated agglomerate particle (CAP) route, were studied using this method. Studies on feasibility of this method for quantitative estimation of plutonium heterogeneity in MOX fuels are discussed in this paper.