  We identify shocked gas in simulated galaxy clusters extracted from the
MareNostrum Universe simulation (Gottloeber et al. 2006) assuming that shock
waves are regions of electron acceleration. We perform flux number counts
within the framework of the non-thermal emission model developed by Hoeft et
al. (2008). Results are presented at two different observing frequencies, i.e.
1.4 GHz and 120 MHz, posing interesting constraints for LOFAR and upcoming
radio telescopes.
