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SIMFUEL replicates the chemical state and microstructure of irradiated fuel. Non-radioactive elements in amounts equivalent to given burnup compositions are added to UO(2) powder. The preparation route features high-energy grinding and spray drying to achieve homogeneous dispersion on a submicrometre scale, and sintering to provide atomic-scale mixing. This leads to a phase structure representative of high-burnup fuels having operated at high temperatures. Extensive characterisation shows solute fission-product atoms dissolved in the oxide matrix, spherical metallic Mo-Ru-Pd-Rh precipitates and ceramic phases. Thermal properties of UO(2) at high temperature are among the most important parameters in assessing fuel behaviour at high burnup. The thermal diffusivity and specific heat of SIMFUEL was measured between 25 and 1500 C, at two laboratories using two different techniques, with good agreement. These data were combined to obtain thermal conductivity. The decrease in thermal conductivity was approximately linear with burnup. Isochronal and isothermal release of ion-implanted krypton from UO(2) and SIMFUEL specimens were measured under reducing conditions for gas concentrations which led to temporary trapping of the gas due to gas-defect interactions. Results for these conditions showed somewhat higher release rates from SIMFUEL.

Additional information

Authors: LUCUTA P G, AECL Research, Chalk River Laboratories, Ontario (CA);VERRALL R A, AECL Research, Chalk River Laboratories, Ontario (CA);HASTINGS I J, AECL Research, Chalk River Laboratories, Ontario (CA);MATZKE H-J, JRC Karlsruhe (DE)
Bibliographic Reference: Paper presented: IAEA Technical Committee Meeting on Fission Gas Release and Fuel Rod Chemistry Related to Extended Burnup, Pembroke (CA), April 27 - May 1, 1992
Availability: Available from (1) as Paper EN 36674 ORA
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