Safety assessment of plutonium mixed oxide fuel irradiated up to 37.7 GW day tonne1

In this irradiation test, the performance safety of (Th,Pu)O2 fuel was evaluated. The fuel pellets were synthesised from powders prepared using a sol gel method to give a product exhibiting an atomically homogeneous distribution of the elements. The fuel pellets, of conventional pressurised water reactor (PWR) dimensions, were encapsulated in zircaloy cladding, and irradiated during four reactor cycles, reaching a burnup of 37.7 GWd/tonne in the KWO pressurised water reactor at Obrigheim, Germany. The irradiation test was performed under representatives conditions. Intermediate inspection of the fuel pin during reactor outages revealed a cladding creep down within the bounds observed for UO2 fuels under similar conditions. Hydriding of the cladding was found predominantly on the outer liner of the duplex cladding. Fission gas analysis revealed a fission gas release of about 0.5%, which is somewhat lower than U-MOX fuels at the same burnup, but they were operated at higher linear heating rate. The Xe/Kr ratio of 11 is much lower than (U,Pu)O2 fuel (typically 16), indicating significant 233U generation and fissioning thereof during the irradiation experiment. Examination of the microstructure indicates that the pellet – cladding gap is almost closed. The grain size remained similar to the fresh fuel (4 µm) and no intragranular porosity was observed.

SOMERS Joseph;  PAPAIOANNOU Dimitrios;  MCGINLEY John;  SOMMER Dieter; 

2013-04-15

ELSEVIER SCIENCE BV

JRC67358

0022-3115,   

http://www.sciencedirect.com/science/article/pii/S0022311513004522,    https://publications.jrc.ec.europa.eu/repository/handle/JRC67358,   

10.1016/j.jnucmat.2013.02.046,