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@ARTICLE{Spilker:865900,
      author       = {Spilker, B. and Linke, J. and Loewenhoff, Th. and Pintsuk,
                      G. and Wirtz, M.},
      title        = {{P}erformance {E}stimation of {B}eryllium {U}nder {ITER}
                      {R}elevant {T}ransient {T}hermal {L}oads},
      journal      = {Nuclear materials and energy},
      volume       = {18},
      issn         = {2352-1791},
      address      = {Amsterdam [u.a.]},
      publisher    = {Elsevier},
      reportid     = {FZJ-2019-05177},
      pages        = {291 - 296},
      year         = {2019},
      abstract     = {The plasma facing first wall in ITER will be armored with
                      beryllium. During operation, the armor has to sustain direct
                      plasma contact during the start-up and ramp-down of the
                      plasma. On top, transient thermal loads originating from a
                      variety of plasma instabilities or mitigation systems are
                      impacting the 8–10 mm thick beryllium tiles. In this
                      work, possible armor thickness losses caused by the expected
                      transient heat loads are reviewed. Applying conservative
                      assumptions, vertical displacement events can cause locally
                      a melt layer with a thickness of up to 3 mm. However,
                      cracks after solidification/cool down are confined to the
                      melt layer and the connection between melt layer and bulk
                      remains strong. Radiative cooling mechanisms can be applied
                      to significantly decrease the melt and evaporation layer
                      thickness. To mitigate the critical damage potential of
                      plasma disruptions, massive gas injections or shattered
                      pellet injections can be deployed to transform the stored
                      plasma energy into radiation, which implies a much more
                      homogeneous distribution of energy to the plasma facing
                      components. For a full power plasma discharge in ITER, these
                      radiative loads can cause temperatures exceeding the melting
                      temperature of beryllium. Experiments have demonstrated that
                      a thickness of 340 µm at the entire first wall armor can
                      be affected by these mechanisms over the lifetime of ITER.
                      Edge localized modes with expected characteristics obtained
                      by fluid model simulations caused fatigue cracks with a
                      depth of up to 350 µm in experimental simulations. The
                      critical heat flux factor FHF above which inflicted damage
                      accumulates with each subsequent pulse has been determined
                      to be in the range of FHF ≈ 9–12 MW m−2 s0.5. The
                      damage from thermal loads below this threshold saturates
                      between 104 and 106 pulses. Neutron irradiation has a
                      deteriorating effect on the thermomechanical properties of
                      beryllium, which strongly influence its resistance against
                      thermally induced damages. The rather low neutron fluence
                      over the lifetime of ITER is expected to reduce the material
                      strength and thermal conductivity by a few tens of percents.
                      If the thickness losses are affected to a similar extent, a
                      sufficient margin of armor thickness will remain. Overall,
                      the damage imposed by radiative loads from massive gas
                      injections or shattered pellet injections is expected to be
                      the dominant force influencing the condition of the first
                      wall armor, at least if all disruptions can be successfully
                      mitigated and the number of vertical displacement events can
                      be constrained to a few occurrences over the service time of
                      ITER.},
      cin          = {IEK-2 / IEK-4},
      ddc          = {624},
      cid          = {I:(DE-Juel1)IEK-2-20101013 / I:(DE-Juel1)IEK-4-20101013},
      pnm          = {174 - Plasma-Wall-Interaction (POF3-174)},
      pid          = {G:(DE-HGF)POF3-174},
      typ          = {PUB:(DE-HGF)16},
      UT           = {WOS:000460107500050},
      doi          = {10.1016/j.nme.2018.12.026},
      url          = {https://juser.fz-juelich.de/record/865900},
}