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@INPROCEEDINGS{Klinkenberg:1016753,
      author       = {Klinkenberg, Martina and Brandt, Felix and Barthel, Juri
                      and Bosbach, Dirk},
      title        = {{S}olid-solution formation of ({B}a,{S}r,{R}a){SO}4:
                      {M}icroscopic approaches},
      reportid     = {FZJ-2023-03739},
      year         = {2023},
      abstract     = {The minerals of the isostructural barite ((Ba,Sr)SO4) group
                      are frequently occurring and characterized by their low
                      solubility. These sulfates are associated with the formation
                      of technically enhanced naturally occurring radioactive
                      material (TENORM). The radioactivity of TENORM is often a
                      result of solid solution formation with 226Ra because of the
                      higher thermodynamic stability compared to the pure
                      endmember RaSO4. The (Ra,Ba,Sr)SO4 is also relevant for the
                      safety assessment of deep geological repositories for spent
                      nuclear fuel. In this contribution, the application of
                      microscopic approaches on the solid-solution formation of
                      (Ba,Sr,Ra)SO4 to understand macroscopic observations will be
                      discussed.A combination of scanning electron microscopy
                      (SEM), energy dispersive x-ray spectrometry (EDX), focused
                      ion beam (FIB), transmission electron microscopy (TEM) as
                      well as time of flight secondary ion mass spectroscopy
                      (ToF-SIMS) and atom probe tomography (APT) was applied to
                      unravel the up-take of 226Ra into (Ba,Sr,Ra)SO4 on a
                      molecular scale. SEM-EDX was used to follow the
                      morphological and chemical evolution of the sulfate
                      particles during the Ra-uptake. The Ra-uptake into the solid
                      was observed by a 3D analysis of complete grains via
                      ToF-SIMS. The FIB, producing very small samples and
                      extremely thin samples for TEM and atom probe tomography
                      (APT), enables the detailed investigation of even highly
                      radioactive materials due to the low radioactivity of the
                      FIB sections. TEM and APT were applied to unravel the
                      details of this recrystallization process from the solid
                      materials perspective, indicating an important role of fluid
                      inclusions and internal porosity typical for these sulfates.
                      Our studies not only show that 226Ra is taken up
                      structurally during recrystallisation of (Ba,Sr)SO4, but
                      also that kinetically controlled initial stages eventually
                      are followed by thermodynamically controlled Ra-uptake which
                      can be described via solid-solution aqueous-solution
                      modeling.},
      month         = {Oct},
      date          = {2023-10-04},
      organization  = {21st Jena Remediation Symposium, Jena
                       (Germany), 4 Oct 2023 - 6 Oct 2023},
      subtyp        = {Invited},
      cin          = {IEK-6 / ER-C-2},
      cid          = {I:(DE-Juel1)IEK-6-20101013 / I:(DE-Juel1)ER-C-2-20170209},
      pnm          = {1411 - Nuclear Waste Disposal (POF4-141)},
      pid          = {G:(DE-HGF)POF4-1411},
      typ          = {PUB:(DE-HGF)24},
      url          = {https://juser.fz-juelich.de/record/1016753},
}