It is generally observed that thermal conductivity of LWR MOX fuel is lower than that of pure UO2 fuel. For MOX, the degradation is usually only interpreted as an effect of the substitution of U atoms by Pu. This hypothesis is however in contradiction with the observations of Duriez and Philiponneau showing that the thermal conductivity of MOX is independent on the Pu content in the ranges 3 to 15 and 15 to 30 wt. % PuO2 respectively. Attributing this degradation to Pu only implies that stoichiometric heterogeneous MOX can be obtained, while we show that any heterogeneity in the plutonium distribution in the sample will introduce a variation in the local stoichiometry which in turn has a strong impact on the thermal conductivity. A model quantifying this effect is presented and a new set of experimental results obtained for homogeneous and heterogeneous MOX fuels is presented and used to validate the proposed model. In irradiated fuels, this effect is predicted to disappear early during irradiation.

STAICU Dragos;  BARKER M.; 

2013-12-16

ELSEVIER SCIENCE BV

JRC76885

0022-3115,   

https://publications.jrc.ec.europa.eu/repository/handle/JRC76885,   

10.1016/j.jnucmat.2013.08.024,