According to the speadsheet (https://docs.google.com/spreadsheet/lv?key=0An54qOfSiXfJdEcyaHAxWURaZTR2eEpEWEFaU0xydXc#gid=0), A 5x5 Reactor with 4 fuel rods in the corners cooled with Cryotheum, should produce 2100 RF/t, however, my reactor, which is set up exactly the same way only produces arround 710 RF/t.