Multiple voltage electron probe microanalysis of fission gas bubbles in irradiated nuclear fuel

The accurate analysis of locally retained fission gas in nuclear fuel is in herently difficult since the physical form under which it is stored varies from an atomic dispersion to bubbles with a diameter of several hundreds of nanometers. One of the techniques that has been applied since more than 20 yr is electron probe microanalysis (EPMA). This technique, however, is dif ficult to apply in a quantitative manner if the studied materials are inhom ogeneous at the scale of the electron-solid interaction volume. In this pap er, a method is developed to analyse a system of gas bubbles distributed in a solid matrix. It is based on the geometric modelling of a gas bubble dis persion and the assessment of its influence on the emitted X-ray intensity. The calculation exploits experimental results acquired at different accele rating voltages. The resulting more accurate analysis of gas retained in nu clear fuel may lead to a better insight in the gas release mechanisms. (C) 2000 Elsevier Science B.V. All rights reserved.