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@PHDTHESIS{Titov:50677,
author = {Titov, Maxim},
title = {{C}haracterisation and final disposal behaviour of
thoria-based fuel kernels in aqueous phases},
volume = {4180},
issn = {0944-2952},
school = {Techn. Hochsch. Aachen},
type = {Dr. (FH)},
address = {Jülich},
publisher = {Forschungszentrum Jülich GmbH Zentralbibliothek, Verlag},
reportid = {PreJuSER-50677, Juel-4180},
series = {Berichte des Forschungszentrums Jülich},
pages = {VII, 143 p.},
year = {2005},
note = {Record converted from VDB: 12.11.2012; Aachen, Techn.
Hochsch., Diss., 2005},
abstract = {Two high-temperature reactors (AVR and THTR) operated in
Germany have produced about 1 million spent fuel elements.
The nuclear fuel in these reactors consists mainly of
thorium-uranium mixed oxides, but also pure uranium dioxide
and carbide fuels were tested. One of the possible solutions
of utilising spent HTR fuel is the direct disposal in deep
geological formations. Under such circumstances, the
properties of fuel kernels, and especially their leaching
behaviour in aqueous phases, have to be investigated for
safety assessments of the final repository. In the present
work, unirradiated ThO$_{2}$,
Th$_{0.906}$,U$_{0.094}$)O$_{2}$,
(Th$_{0.834}$,U$_{0.166}$)O$_{2}$ and UO$_{2}$ fuel kernels
were investigated. The composition, crystal structure and
surface of the kernels were investigated by traditional
methods. Furthermore, a new method was developed for testing
the mechanical properties of ceramic kernels. The method was
successfully used for the examination of mechanical
properties of oxide kernels and for monitoring their
evolution during contact with aqueous phases.The leaching
behaviour of horia-based oxide kernels and powders was
investigated in repositoryrelevant salt solutions, as well
as in artificial leachates. The influence of different
experimental parameters on the kernel leaching stability was
investigated. It was shown that thoria-based fuel kernels
possess high chemical stability and are indifferent to
presence of oxidative and radiolytic species in solution.
The dissolution rate of thoria-based materials is typically
several orders of magnitude lower than of conventional
UO$_{2}$ fuel kernels. The life time of a single intact
(Th,U)O$_{2}$ kernel under aggressive conditions of salt
repository was estimated as about hundred thousand years.
The importance of grain boundary quality on the leaching
stability was demonstrated. Numerical Monte Carlo
simulations were performed in order to explain the results
of leaching experiments.},
cin = {ISR},
cid = {I:(DE-Juel1)VDB182},
pnm = {Nukleare Sicherheitsforschung},
pid = {G:(DE-Juel1)FUEK249},
typ = {PUB:(DE-HGF)11 / PUB:(DE-HGF)3},
url = {https://juser.fz-juelich.de/record/50677},
}