Taming the Chain Reaction

Moderators, delayed neutrons and control

An interactive lesson with 6 steps, about 5 minutes: you predict, drag and solve, with instant feedback on every answer. It runs in your browser and needs JavaScript.

What you’ll learn

• Moderators slow fast neutrons by collisions; hydrogen works best per collision.
• Delayed neutrons (about 0.65%) make reactors controllable.
• A negative void coefficient makes overheating reduce power automatically.

Steps

1. Slow neutrons work best
2. Choosing a moderator
3. Billiard-ball physics
4. Delayed neutrons
5. Neutrons to spare
6. Built-in safety