Step 1: Input the core (interior) size of the reactor: × ×

Step 2: Click on the fuel you want to use in the table below. Most modpacks use the default config, except for E2E and PO3. Alternatively, you can manually enter the fuel data in the textboxes below. The fuel data can be found in the tooltip of the fuel item. Do not use the data shown in JEI, they may be incorrect. You can also use IC2 and ExtremeReactors' fuels. See below the table for more details.

Fuel Base Power: RF/t

Fuel Base Heat: H/t

For ExtremeReactors' Yellorium or Blutonium, click LEU-235 Normal and then click here once.
For IC2's Enriched Uranium Nuclear Fuel, click LEU-235 Normal and then click here once.
For IC2's MOX Nuclear Fuel, click MOX-239 and then click here once.

Step 3: If you want to limit the usage of a type of block, enter the maximum number allowed in the table below. Enter zero to completely disable that block. You can hover over the acronym to see the full name of each block. Active coolers are disabled by default. You can enable them by removing the zeros.

Step 4: Load the cooling rate data by clicking on one of the following modpack configs: Default E2E PO3. Alternatively, you can enter the data yourself. Passive cooling rates are in the tooltip of each cooler item. Active cooling rates are in JEI.

Step 5: Adjust the options below and click “Run” to start the optimization.
Ensure active coolers are accessible by piping.
Only generate heat neutral reactor.
Optimize for power.
Optimize for breeding (maximize fuel consumption rate).
Optimize for efficiency.
X symmetry Y symmetry Z symmetry
Use reinforcement learning (requires more memory, slightly slower but can produce better design)
The most efficient reactor doesn't produce the most power. To get a efficient reactor that can still generate lots of power, you should optimize for power while limiting the cell count using the “Max Allowed” box for []. To get the ideal cell count, divide the fuel's base processing time by the time you want a fuel to last. Enabling symmetry and/or limiting block counts often speeds up the algorithm. The algorithm uses fixed seed: different runs will always yield the same results unless there is an update to the algorithm (last update: 2024-03-08). You can use Building Gadgets to automate the building of your reactor. To do so, save the JSON of your design, load it up in Hellrage's Reactor Planner, and then click “Generate BG string”. Then you can paste it in the Template Manager.
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