Microacoustic Techniques to Assess the Local Characteristics of Irradiated Fuel Materials

Abstract

The thermomechanical analysis of PCMI (Pellet to Clad Mechanical Interaction) failure risk is one of the major concern when designing the nuclear he1 rod. Code simulations are used for such analysis. The accuracy of the simulations requests a correct evaluation of the local properties of the materials. Improvement are still needed in the local characterisation of high burn-up he1 materials. Aiming this target, microacoustic techniques have been developed to perform local characterisations of the elastic properties on fuel materials, and of the pore volume fraction as well. A single set-up adapted to operate in hot cell by two complementary techniques, acoustic microscopy and microechography, has been designed. Working at 15 MHz, acoustic microscopy provides local measurements of the Rayleigh velocity through the study of the acoustic signature. Microechography used at a 40 MHz frequency give access to the longitudinal velocity. The local elastic constants and the relative pore volume can be deduced from the Rayleigh and the longitudinal velocities.