Report on the effect of dopants on FLASH sintering of enhanced UO₂

Technical Report · Fri Jun 28 04:00:00 EDT 2019

DOI:https://doi.org/10.2172/1711331· OSTI ID:1711331

Kardoulaki, Erofili ^[1]

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1. Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

Large grained UO₂ can be achieved through the addition of dopants such as, Cr, Al, Nb and Mg. The enhanced microstructure can enable slower fission gas release that reduces pressure build up in the fuel rods and better mechanical properties that can alter the pellet cracking behavior and, therefore, limit accident prone pellet cladding loading. UO₂ fuel is sintered through conventional sintering methods that require high temperatures and long sintering times. Field assisted sintering techniques like flash sintering use current and voltage to enable sintering of ceramics at low temperatures and short times. Flash sintering has been demonstrated for sintering UO₂ to high densities. In this work, this technique has been applied to Cr-doped UO₂ to assess the feasibility of the technique for grain enhancement. Doped UO₂ samples below and above the solubility limit of Cr into UO₂ have been assessed. The results show that grain enhancement was not possible in either case and this was attributed to the low temperatures and sintering times that make flash sintering attractive. For the Cr-doped sample below or near the solubility of Cr, it is postulated that the temperatures were not high enough to actually dissolve it into solution in the UO₂ lattice. For the Cr-doped sample above the solubility limit of Cr, secondary phases were identified via SEM and EDS, as expected. Follow up work should be carried out to assess if flash sintering can produce grain enlargement for UO₂ feedstocks with dopants already in solid solution such as UO₂ produced via sol-gel or modified direct denitration method.

• Research Organization: Los Alamos National Laboratory (LANL), Los Alamos, NM (United States)
• Sponsoring Organization: USDOE Office of Nuclear Energy (NE)
• DOE Contract Number: 89233218CNA000001
• OSTI ID: 1711331
• Report Number(s): LA-UR--19-25966
• Country of Publication: United States
• Language: English

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