  The supernova remnant Cassiopeia A is a prime candidate for accelerating
cosmic ray protons and ions. Gamma rays have been observed at GeV and TeV
energies, which indicates hadronic interactions, but they could also be caused
by inverse-Compton scattering of low-energy photons by accelerated electrons.
We seek to predict the flux of nuclear de-excitation lines from Cas A through
lower-energy cosmic rays and to compare it with COMPTEL measurements. Assuming
a hadronic origin of the high-energy emission, we extrapolate the cosmic ray
spectrum down to energies of 10 MeV, taking into account an equilibrium
power-law momentum spectrum with a constant slope. We then calculate the
nuclear line spectrum of Cassiopeia A, considering the most prominent chemical
elements in the MeV band and their abundances as determined by X-ray
spectroscopy. We show that the predicted line spectrum is close to the level of
the COMPTEL sensitivity and agrees with conservative upper limits.
