A New Methodology for Plutonium Homogeneity Level Determination in Sodium Fast Reactor Fresh Fuel From Uranium and Plutonium X-ray Mappings

In the framework of the Fourth Generation program, the CEA studies a new concept of Sodium Fast Reactor (SFR) named ASTRID [1]. The reference fuel chosen for the reactor starting is uranium and plutonium mixed oxides. This type of fuel had been fabricated until 1999 during the PHENIX (French SFR prototype) operation. The industrial process led to homogeneous uranium /plutonium distributions in compliance with the fabrication specifications. Nowadays, specific R&D programs deal with innovative processes in order to obtain (UPu)O2 fuel with the same level of homogeneity [2]. In order to evaluate this feature, microstructural characterizations especially uranium and plutonium distributions are carried out using Electron Probe Micro Analysis (EPMA). Data post-treatments consist in measuring plutonium homogeneity level on a micrometer scale using initial mappings. This paper focuses on the development of a calculation tool using EPMA mappings which allows to qualify plutonium homogeneity level of industrial fuels, and to compare it to new R&D fuels developed in the frame of ASTRID project.