Reactor Overview

Fission reactors provide reliable, long term, compact sources of power in situations where solar panels might not be appropriate. However, their operation requires a few new concepts which are outlined here.

Reactor Basics

To produce energy, a reactor only requires a supply of Enriched Uranium. When activated, the reactor will slowly consume its fuel and transmute it into Depleted Fuel. This is a mass-neutral process. When the reactor has run out of fuel or its depleted Fuel storage is full, it will no longer produce energy. Reactors parts have generally been configured to run for about 5 Kerbal years at full power without refuelling. This can be extended by running at lower powers or turning off the reactor, or refuelling the reactor from Nuclear Fuel containers.

Heat Management

As a reactor produces power, it also produces waste heat. This needs to be dissipated into space via radiation or the reactor will suffer damage and eventually a complete meltdown and become useless. Once the reactor is turned on, you will notice its core temperature climb rapidly to a nominal operating temperature. If you do not have the capacity to dump the reactor's waste heat the core will continue to heat up with predictable effects.

Heat is removed through the use of radiators. In the VAB parts list, the Fission Reactor component indicates the amount of heat generated in kilowatts (kW) at full throttle ("Required Cooling"). This will be lower if the reactor is operated at partial capacity. You should match this Required Cooling number with the Core Heat XFer shown on Radiator parts. If your vessel's total Core Heat Xfer matches or exceeds the total Required Cooling, you will be fine. Do of course recall that drill and resource converters on your ship also require cooling, so if you plan to run reactors and resource equipment at the same time, pack enough radiators for both.

As an example, the reactor shown here requires 3500 kW of cooling. In the stock game, the Large Thermal Control System provides 1 MW, or 1000 kW of cooling. This means that for it to function, I will need 4 of them. For best mass efficiency, I could use 3 large TCS, and some smaller radiators to make up the missing 500 kW.

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Important Note: static (Edge and Panel) radiators in the stock game only transfer heat from parts up to one part away. Therefore, if using these for reactor cooling, make sure they are attached directly to the reactor or directly to a part that is reactor adjacent. The deployable Thermal Control Systems and most other mod radiators can be placed anywhere on the ship.

Reactor Control Window

The mods provides a special control window where you can see at a glance the set of reactors that are on your vessel and manage their functions. This can be very useful if you have a large ship with a bunch of reactors. Most of these functions/data displays are also available in the Part Action Window when you right click a reactor

• Reactor Toggle: The on/off state of the reactor
• Reactor Power Slider: This control allows you to set the reactor's output
• Reactor Temperature: The current rector temperature
• Reactor Temperature Bar: Visual representation of temperature
• Nominal Temperature: The point at which the reactor is in nominal operation
• Critical Temperature: Above this temperature, the reactor's core will take damage
• Power Production: The current amount of Electric Charge per second produced
• Heat Production: The current amount of heat that needs to be radiated
• Estimated Core Life: The estimated amount of time the reactor will operate for given current fuel load
• Core Health: The amount of damage the core has incurred
• Temperature Shutoff: The temperature at which to automatically shut off the reactor
• Warp Shutoff: The timewarp level at which to automatically shut off the reactor
• Reactor Name: The customizable reactor name
• Reactor Icon: The customizable reactor icon
• Reactor Customization: Click here to customize the reactor's name, eg. "Life support power" or similar and icon

Reactor Repair

In the course of your operations, it's possible that a reactor may overheat and become damaged. Damage occurs when the core is over the Critical Temperature. Damage reduces the amount of power the reactor can produce. Repairs can be made in the field to some extent by a highly qualified Engineer (Level 5 is required). If the reactor has a core integrity of 10% or lower, repairs cannot be made. Additionally, because field repair of a precision instrument is difficult, cores cannot be repaired above 75%. As an exception to this, if the reactor is currently landed at the KSC, repairs are possible up to 100%.

Nuclear Fuel Handling

As the fuel casks and waste are very dangerous to handle, Enriched Uranium and Nuclear Fuel can only be transferred within a vessel if a qualified engineer is onboard. A Level 1 Engineer is required to transfer Enriched Uranium and a Level 3 Engineer is required to transfer DepletedFuel. Transferring is done outside the usual fuel transfer interface - simply click on a part that can store EnrichedUranium and DepletedFuel and you'll get the option to Transfer Waste or Transfer Fuel. Once selected, you can click on the target part to move the waste or fuel there.

Nuclear Fuel Processing and Production

By using the Whirlijig processor, Ore can be refined into Enriched Uranium. This process is expensive and wasteful - a lot of Ore is required to produce a small amount of uranium.

It addition, the Whirlijig can also reprocess Depleted Fuel at a 50% efficiency, converting half of it into usable Enriched Uranium. This can be used to significantly extend reactor life without mining.