Determination of the pressure in micrometric bubbles in irradiated nuclear fuels

In oxide nuclear fuels, at high burn-up or during temperature periods such as ramp tests, out-of-pile heating any irradiations linear heat rates, fission gases can form micrometric quasi-micrometric bubbles. During nominal operations, these bubbles participate to the pellet swelling, decrease of fuel thermal conductivity and are involved in mechanisms leading gas release. events involving a increase, resulting increase internal pressure might play role fragmentation opening grain boundaries. The densities inside therefore one useful experimental information for understanding behaviour, behaviour code progress validation. Two methods were developed evaluate density bubbles, using electron probe micro analyser, secondary ion mass spectrometry focused beam scanning microscope together. first method provides mean all given area. second single selected bubble. addition density, 3D size shape bubble is measured be related result. this work, applied formed centre PWR Cr doped UO2 38.8 GWd/tU after test Osiris reactor, with 12 h plateau 470 W/cm, 62.8 on structure rim. Both show pressures reached