The Nuclear Reactor is the most powerful generator in Industrial Craft 2, splitting uranium fuel rods into EU across a 20,000-second cycle (about 5 hours 33 minutes). A single Fuel Rod (Uranium) delivers 5 EU/t and at least 2 million EU per cycle, while a well-balanced core extracts more than 32 million EU from the same rod. The Nuclear Reactor opens like a chest: fuel rods, Heat Vents, coolant cells, plating and Neutron Reflectors are placed directly into the internal grid, and up to six Reactor Chambers mounted on the sides enlarge that grid. Each burning fuel rod also generates heat every second, and if the cooling layout cannot absorb that heat, components burn out and the reactor hull marches toward a meltdown.

Heat decides everything: at 40% hull heat flammable blocks in a 5×5×5 cube around the reactor catch fire, at 50% water evaporates, at 70% radiation damages every entity in a 7×7×7 cube, and at 100% hull heat the Nuclear Reactor explodes violently. Neighbouring fuel rods exchange neutron pulses worth 5 EU/t each, so two Fuel Rods (Uranium) placed side by side jointly produce 20 EU/t, while a lone Quad Uranium Cell delivers 60 EU/t at the cost of 96 heat per second. Enclosing the core in a 5×5×5 shell of Reactor Pressure Vessels switches the Nuclear Reactor to fluid mode, where heat leaves the hull as Hot Coolant and drives Steam Generators instead of raw EU. Build a three-metre wall of reinforced stone around the reactor hall, connect small cores with copper cable and big cores with gold or HV cable, and cut the power with a lever before swapping spent rods.