From the notice

The Heat Pipe Reactor Fire Mitigation and Suppression System from Los Alamos National Laboratory, transforms the heat pipes inside an alkali metal-cooled nuclear reactor from passive thermal conduits into active, sensor-driven fire defense components, giving designers of advanced small and microreactors a layered, automated safeguard against one of the most challenging hazards in their systems. By combining an inert gas buffer, a phase change material jacket, automated suppressant injection at multiple points and optional neutron-absorber dispersion into the reactor core, the system delivers redundant protection that responds within milliseconds of detecting fire-like conditions. This system enables advanced reactor developers to meet stringent safety expectations for remote, unattended and space-constrained deployments without redesigning the core architecture around bulky external suppression equipment. How it Works During normal operation, each heat pipe carries thermal energy away from the reactor core through the evaporation and condensation of an alkali metal working fluid, while valves connecting the heat pipe to external suppressant chambers remain closed. Temperature and pressure sensors continuously monitor the heat pipe reactor core and the valves near each heat pipe end, feeding data to a controller that compares readings against predefined thresholds. When a reading crosses the first threshold, the controller opens a valve and forces a fire suppressant material, typically a boron compound, into the interior of the heat pipe.

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