v2026.1.24

New Features

• Geiger counter audio cue added on neutron-uranium collision
• Mute audio with m
• Manual adjustment of Control Rods with UP and DOWN
• Switch Control Rod mode with c
• Control Rod mode and audio state reporting added in the statistics at the bottom of the screen
• Instructions for the new controls added upon launch

Installation

Download reactor.jar and run it using Java

Tip

On most systems, you can double click the file or right click it and select Open with -> Java SE Platform Binary (or similar)
Or run java -jar reactor.jar

If you encounter issues:

• Use Java 8
• On Windows, run using the Command Prompt or Powershell

v2026.1.23

New Features

• Neutron Moderator Demo added
• Demo Mode information popup on launch added
• Demo Mode selector on launch added

Installation

Download reactor.jar and run it using Java

Tip

On most systems, you can double click the file or right click it and select Open with -> Java SE Platform Binary (or similar)
Or run java -jar reactor.jar

If you encounter issues:

• Use Java 8
• On Windows, run using the Command Prompt or Powershell

v2026.1.18

New Features

• All Neutrons start as unmoderated and fast moving, unable to interact with Uranium or Control Rods.
• Unmoderated Neutrons hitting a neutron moderator will bounce off and lose speed, becoming moderated.
• These neutrons will then be able to interact with other elements of the reactor.

Note

Details regarding demo modes showcasing various features can be found in src/Reactor/Constants.java. To use them, clone the project, and edit the DEMOVERSION variable.

Installation

Download reactor.jar and run it using Java

Tip

On most systems, you can double click the file or right click it and select Open with -> Java SE Platform Binary
Or run java -jar reactor.jar

If you encounter issues:

• Use Java 8
• On Windows, run using the Command Prompt or Powershell

v2026.1.17

Implemented Features

• Neutrons have a random chance to be emitted by non-fissile atoms
• Neutrons colliding with Uranium (blue) are absorbed and 3 new neutrons are emitted
• Uranium undergoing fission has a random chance to turn into xenon
• Neutrons colliding with Xenon will revert to a non-fissile element
• Uranium is randomly introduced to the simulation to maintain the percentage in the reactor
• Water has a random chance of absorbing neutrons
• Water can heat up and evaporate, losing its ability to absorb neutrons
• Control rods absorb neutrons
• Control rods are automatically moved up or down based on the number of neutrons in the reactor
• Info about the simulation can be found along the bottom of the screen, including the number of neutrons (N), Uranium atoms (U), and Xenon atoms (XE) in the reactor, the status of the control rods (CR), the framerate, and the graphics device in use.

Note

Details regarding demo modes showcasing various features can be found in src/Reactor/Constants.java. To use them, clone the project, and edit the DEMOVERSION variable.

Installation

Download reactor.jar and run it using Java

Tip

On most systems, you can double click the file or right click it and select Open with -> Java SE Platform Binary
Or run java -jar reactor.jar

If you encounter issues:

• Use Java 8
• On Windows, run using the Command Prompt or Powershell