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The thermal behaviour of nuclear fuel is dependent on its thermal conductivity, which alters during operation as a result of structural changes and the accumulation of fission products. Numerical models suggest that, as burnup progresses, the release of fission gases reduces conductivity. It is, however, very difficult to take direct measurements of conductivity on irradiated fuel samples. For this study a number of UO(2) samples were made in which burnup was simulated by mixing in the solid fission products (SIMFUEL). This is essentially similar to normal irradiated fuel, except that fission gases are absent. Thermal diffusivity of the SIMFUEL was measured by the laser flash technique and by means of a sinusoidally modulated electron beam. Specific heat, needed for converting diffusivity into conductivity, was measured by DSC or derived from enthalpy measurements, and was also established mathematically using the Kopp-Neumann Rule. The specific heat of SIMFUEL is 1-2% higher than that of UO(2). Thermal resistivity rises in an approximately linear relationship to burnup.

Additional information

Authors: TASMAN H A, JRC Karlsruhe (DE)
Bibliographic Reference: Paper presented: Arbeitskreis Thermophysik, Wien (AT), May 14-15, 1992
Availability: Available from (1) as Paper DE 36974 ORA
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