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Thermal properties of UO(2) at high temperature are among the most important parameters in assessing fuel behaviour at high burnup. Reduction in thermal conductivity occurs in the fuel during irradiation because of fission-gas bubbles, fission products (dissolved and precipitated) and O/U ratio increase. SIMFUEL (SIMulated high-burnup UO(2) FUEL) provides a non-radioactive analogue to irradiated fuel. Hyperstoichiometric SIMFUEL and UO(2), with selected O/U ratios are prepared by annealing specimens in an oxidising atmosphere, so the effect of the stoichiometry on thermal properties of the fuel can be investigated. The thermal conductivity of stoichiometric SIMFUEL has been reported to be lower than that of the pure UO(2). The thermal diffusivity and specific heat of annealed SIMFUEL and UO(2) were measured between room temperature and 1500 C and the data combined to obtain thermal conductivity. Thermal conductivity of SIMFUEL decreases as the burnup increases. Preliminary results on hyperstoichiometric SIMFUEL show that a small increase in the O/U ratio (2.001) results in a slight decrease in the thermal conductivity. A reduction by 4 % has been observed at 400 C in the hyperstoichiometric SIMFUEL.

Additional information

Authors: LUCUTA P G, AECL Research, Chalk River Laboratories (CA);VERRALL R A, AECL Research, Chalk River Laboratories (CA);MATZKE H-J, JRC Karlsruhe (DE);HASTINGS I J, AECL Head Office, Ottawa (CA)
Bibliographic Reference: Paper presented: 3rd International Conference on CANDU Fuel, Chalk River (CA), October 4-8, 1992
Availability: Available from (1) as Paper EN 37283 ORA
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