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@ARTICLE{Moormann:136055,
      author       = {Moormann, R.},
      title        = {{F}ission {P}roduct {T}ransport and {S}ource {T}erms in
                      {HTR}s: {E}xperience from {AVR} {P}ebble {B}ed {R}eactor},
      journal      = {Science and technology of nuclear installations},
      publisher    = {Hindawi Publishing Corporation},
      reportid     = {PreJuSER-136055},
      pages        = {597491},
      note         = {Record converted from JUWEL: 18.07.2013},
      comment      = {Science and Technology of Nuclear Installations},
      booktitle     = {Science and Technology of Nuclear
                       Installations},
      abstract     = {Fission products deposited in the coolant circuit outside
                      of the active core play a dominant role in source term
                      estimations for advanced small pebble bed HTRs, particularly
                      in design basis accidents (DBA). The deposited fission
                      products may be released in depressurization accidents
                      because present pebble bed HTR concepts abstain from a gas
                      tight containment. Contamination of the circuit also hinders
                      maintenance work. Experiments, performed from 1972 to 88 on
                      the AVR, an experimental pebble bed HTR, allow for a deeper
                      insight into fission product transport behavior. The
                      activity deposition per coolant pass was lower than expected
                      and was influenced by fission product chemistry and by
                      presence of carbonaceous dust. The latter lead also to
                      inconsistencies between Cs plate out experiments in
                      laboratory and in AVR. The deposition behavior of Ag was in
                      line with present models. Dust as activity carrier is of
                      safety relevance because of its mobility and of its sorption
                      capability for fission products. All metal surfaces in
                      pebble bed reactors were covered by a carbonaceous dust
                      layer. Dust in AVR was produced by abrasion in amounts of
                      about 5 kg/y. Additional dust sources in AVR were ours oil
                      ingress and peeling of fuel element surfaces due to an air
                      ingress. Dust has a size of about 1 μm, consists mainly
                      of graphite, is partly remobilized by flow perturbations,
                      and deposits with time constants of 1 to 2 h ours. In
                      future reactors, an efficient filtering via a gas tight
                      containment is required because accidents with fast
                      depressurizations induce dust mobilization. Enhanced core
                      temperatures in normal operation as in AVR and broken fuel
                      pebbles have to be considered, as inflammable dust
                      concentrations in the gas phase.},
      cin          = {IEF-6},
      ddc          = {600},
      cid          = {I:(DE-Juel1)VDB814},
      typ          = {PUB:(DE-HGF)16},
      doi          = {10.1155/2008/597491},
      url          = {https://juser.fz-juelich.de/record/136055},
}