Editing Thorium Reactor Safety Features (section)

=== 2. The Freeze Plug ===

A '''freeze plug''' (also called a freeze valve or drain plug) is a small section of the reactor's drain pipe that is kept frozen solid by an active cooling system. If power to the cooling system is lost for any reason — whether through equipment failure, accident, earthquake, cyberattack, or deliberate shutdown — the freeze plug melts automatically within minutes.

When the plug melts, the liquid fuel salt drains by gravity into a subcritical catch basin below the reactor. In this configuration:
* The chain reaction stops because the geometry no longer supports criticality.
* The fuel solidifies as it cools.
* Decay heat is dissipated passively through the catch basin walls by natural convection.
* No operator action, no external power supply, and no emergency pumping systems are required.

This is in direct contrast to the Fukushima accident, where three reactors suffered meltdown because the emergency cooling pumps lost power after the tsunami disabled the backup generators, and the operators could not maintain cooling of the solid fuel cores.