  Owing to the high stored energy of ITER plasmas, the heat pulses due to
uncontrolled Type I edge localized modes (ELMs) can be sufficient to melt the
top surface of several poloidal rows of tungsten monoblocks in the divertor
strike point regions. Coupled with the melt motion associated with tungsten in
the strong tokamak magnetic fields, the resulting surface damage after even a
comparatively small number of such repetitive transients may have a significant
impact on long-term stationary power handling capability. The permissible
numbers set important boundaries on operation and on the performance required
from the plasma control system. Modelling is carried out with the recently
updated MEMENTO melt dynamics code, which is tailored to tackle melt motion
problems characterized by a vast spatio-temporal scale separation. The crucial
role of coupling between surface deformation and shallow angle heat loading in
aggravating melt damage is highlighted. As a consequence, the allowable
operational space in terms of ELM-induced transient heat loads is
history-dependent and once deformation has occurred, weaker heat loads,
incapable of melting a pristine surface, can further extend the damage.
