  JOREK is an advanced non-linear simulation code for studying MHD
instabilities in magnetically confined fusion plasmas and their control and/or
mitigation. A free-boundary and resistive wall extension was introduced via
coupling to the STARWALL and CARIDDI codes, both able to provide dense response
matrices describing the electromagnetic interactions between plasma and
conducting structures. For detailed CAD representations of the conducting
structures and high resolutions for the plasma region, memory and computing
time limitations restrict the possibility of simulating the ITER tokamak. In
the present work, the Singular Value Decomposition provided by routines from
the ScaLAPACK library has been successfully applied to compress some of the
dense response matrices and thus optimize memory usage. This is demonstrated
for simulations of Tearing Mode and Vertical Displacement Event instabilities.
An outlook to future applications on large production cases and further
extensions of the method are discussed.
