Editing Thorium Reactor Safety Features (section)

=== 1. Negative Temperature Coefficient of Reactivity ===

In LFTR and MSR designs, as the reactor temperature increases, the rate of fission '''automatically decreases'''. This occurs through three mechanisms:

* '''Doppler broadening''': As thorium heats up, it absorbs more neutrons (the Doppler effect), leaving fewer neutrons to sustain the chain reaction. Power decreases.
* '''Thermal expansion of the fuel''': As the liquid fuel salt heats up, it expands, pushing fuel out of the active core region. With less fuel in the core, fission slows.
* '''Graphite moderator''': Heating the graphite changes its neutron moderation properties.

The net result is that a LFTR will naturally throttle back its own power output if it overheats — the opposite of the positive feedback that contributed to the Chernobyl accident, where increasing power caused increasing instability.