Using Forge 10.13.0.1200 on Big reactors 0.4.0X4, the creating a world makes the following error: http://pastebin.com/2GaKEJC8. The game then drops back to the main screen, only other installed Mods are:
BigReactos 0.4.0X4
ThermalExpansion 4.0.0B3-11
ThermalFoundation 1.0.0B1-6
CoFHLib 1.0.0B3-20
CoFHCore 3.0.0B3-26
CCC 0.2.9

Fixed in 0.4.0X5 already :)

Thanks!