Xenon migration and trapping in doped ThO2

Transport properties of I, Te and Xe in thoria–urania SIMFUEL

“…Iodine and tellurium should have significant change in their diffusion characteristics by their chemical affinities to the metallic fission products. Xenon diffusion reportedly takes place through MO 2 -trivacancy [2], or, tetravacancy complex of MO 2 and a cation [4]; substitutional vacancies of cation or anion are seen to have very little role [6,7]. Metal oxides like magnesia, niobia added for activated sintering and densification of the thoria based fuel can lead to formation of trivacancies by partial loss of the MgO component from the lattice during the high temperature treatment.…”

Trapping and diffusion of fission products in ThO2 and CeO2

“…Due to the importance of thoria in the nuclear industry, a number of investigations on the release and transport behavior of fission gases and volatiles in thoria and thoria-based fuels have been reported; [4,[10][11][12][13][14][15][16] however, significant discrepancies exist in the migration energy and diffusion mechanism [10]. For example, Shiba [17] reported a high energy barrier of 4.95 eV for xenon release from thoria-6% urania (UO 2 ) and suggested that Xe transport occurred through a tetra-vacancy mechanism.…”

ThO<sub>2</sub> and (U,Th)O<sub>2</sub> processing—A review

“…Sintering being a diffusion controlled process, speeding up the cation will also promote sintering. Matzke [39,40] determined that the diffusion of uranium in UO 2 and ThO 2 is enhanced by several times in the presence of niobium. At Nuclear Fuel Complex, India, it was found that doping by Nb 2 O 5 lowered the sintering temperature of ThO 2 to 1150˚C [41,42].…”