Nuclear fuel elastic properties: application of local nondestructive acoustic methods on UO2, UMo, HTR fuels

In 2001 we have presented a paper in which our approach and first results concerning the effect of porosity or simulated burnup on UO2 mechanical properties were given. In this new communication, these data have been extended. On irradiated fuel, we show that from 0 to 100 GWj/tU a decrease (25 %) of the elastic moduli, mainly due to porosity and fission products occurs. Furthermore, the intrinsic elastic properties of the fuel (this means corrected from porosity) decrease between 30 GWj/tU and 75 GWj/tU. From 75 to 100 GWj/tU, an increase is then observed and the fuel recovers elastic moduli similar to these measured on non irradiated UO2. This increase, which is not observed on SimFuel seems to be an intrinsic characteristic of high burn-up restructured fuels. More recently, measurements on new nuclear fuels such as UMo and HTR particles have been performed and show that acoustic microscopy could also give interesting information. (author)