Insulators in thermionic reactors must be able to withstand high temperature and neutron irradiation. Results from a series of earlier experiments on polycrystalline alumina show that micro‐cracking and volume expansion are two major mechanical instabilities under fast neutron irradiation at high temperatures. This micro‐cracking in polycrystal alumina is due to the internal stress generation from the anisotropic growth of random alumina grains. The irradiation induced volume expansion may also lead to complex stress states when the component is fabricated by bonding alumina with other materials having a different volume expansion rate under neutron irradiation. This paper is devoted to a comparison of the stress distribution in polycrystalline alumina with sapphire and polycrystalline yttria via modeling using an finite element analysis. It was found that intergranular stresses are insignificant in the two latter cases. However both ceramics exhibited high levels of macrostresses when they were incorporated in a sheath insulator configuration. Implications of the findings and comparison with experimental results will be provided.


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    Title :

    Effects of neutron irradiation on insulators for thermionic space nuclear reactor applications


    Contributors:

    Conference:

    Proceedings of the tenth symposium on space nuclear power and propulsion ; 1993 ; Albuquerque, New Mexico (USA)


    Published in:

    Publication date :

    1993-01-10


    Size :

    7 pages





    Type of media :

    Conference paper


    Type of material :

    Electronic Resource


    Language :

    English




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