There are limitations, but they require much, MUCH larger systems.
You can easily verify that more than 90000 atoms are possible, by inserting a replicate 2 2 2 command into the input right after the read_data command in the examples/reaxff/FC folder.
While the 30000 atom simulation does not crash, its thermo output is highly suspicious with its unusually large fluctuations. That indicates that some of your simulation settings are problematic or the potential parameters not suitable for your geometry. Upon closer inspection, it seems that your “units” setting is wrong. You are using “units metal”, but all ReaxFF force field files that I know require “units real”.