  Time-dependent cooling processes are of paramount importance in the evolution
of astrophysical gaseous nebulae and, in particular, when radiative shocks are
present. The present work introduces a necessary set of tools that can be used
to model radiative astrophysical flows in the optically-thin plasma limit. We
aim to provide reliable and accurate predictions of emission line ratios and
radiative cooling losses in astrophysical simulations of shocked flows.
Moreover, we discuss numerical implementation aspects to ease future
improvements and implementation in other MHD numerical codes. The most
important source of radiative cooling for our plasma conditions comes from the
collisionally-excited line radiation. We evolve a chemical network, including
29 ion species, to compute the ionization balance in non-equilibrium
conditions. After a series of validations and tests, typical astrophysical
setups are simulated in 1D and 2D, employing both the present cooling model and
a simplified one. The influence of the cooling model on structure morphologies
can become important, especially for emission line diagnostic purposes.
