Abstract
ThO2 containing around 2 to 3 % U233O2 is considered as fuel for the forthcoming Indian Advanced Heavy Water Reactor (AHWR). High-density ThO2-UO2 pellets have been fabricated by powder metallurgy route using ThO2 and U3O8 powders as the starting materials. U3O8 decomposes to UO2 during high temperature sintering and forms a solid solution with ThO2. The densification behaviour and sintering kinetics of the above were evaluated using a high temperature dilatometer using constant heating rate experiments. To evaluate the activation energy of sintering, a master sintering curve approach has been used. The activation energy for sintering for the above composition in air was found to be 500 kJ/mol.
Highlights
ThO2 containing around 2 to 3 % U233O2 is considered as fuel for the forthcoming Indian Advanced Heavy Water Reactor (AHWR), which is being developed with the specific aim of utilizing thorium for power generation since India has vast reserves of thorium
Slower heating rates lead to densification at lower temperatures since more time for mass transport and diffusion is available until a given temperature is reached
Most sintering models can be used to evaluate the value of the activation energy of sintering, an Arrhenius plot of ln strain rate (ε) versus the reciprocal of the absolute temperature is usually used for the evaluation
Summary
ThO2 containing around 2 to 3 % U233O2 is considered as fuel for the forthcoming Indian Advanced Heavy Water Reactor (AHWR), which is being developed with the specific aim of utilizing thorium for power generation since India has vast reserves of thorium. Large-scale production of these pellets is carried out by processes involving milling, precompaction and granulation followed by cold compaction and high temperature sintering. One of the ways to increase sintering rates is by decreasing the mean particle size. To determine the underlying physical mechanisms of sintering for a given material system, one must know the kinetic mechanisms by which densification and grain growth occur during sintering. This has been done experimentally by determining the activation energy for sintering and comparing that measured value to values reported elsewhere for each possible mass transport mechanism. The output of this result was used to generate the activation energy for sintering
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