Reactor Technology Library

SFRs use liquid sodium metal as coolant instead of water, operating at ~500°C. The fast neutron spectrum means these reactors can actually consume the long-lived radioactive waste from conventional reactors as fuel — a fundamentally different relationship with the nuclear fuel cycle. Russia has operated SFRs commercially for decades. The US has not operated one since the 1990s.

HTGRs use helium gas as coolant, achieving the highest operating temperatures of any reactor type — up to 950°C. This makes them uniquely valuable for industrial applications that need high-temperature process heat: hydrogen production, steel manufacturing, chemical synthesis, desalination. The pebble bed design circulates TRISO fuel spheres continuously through the reactor, enabling online refueling. China currently operates the world's first commercial pebble bed HTGR.

FHRs combine two advanced technologies: fluoride salt coolant and TRISO particle fuel. The molten salt operates at 600-700°C — hot enough to produce industrial process heat for hydrogen, steel, and chemical production. The TRISO fuel is physically incapable of melting, providing passive safety. The critical challenge: the Flibe coolant requires isotopically separated Lithium-7, which has no Western commercial supplier.

LWR-SMRs apply the same proven physics as every commercial reactor built since the 1950s, scaled down to 50-300 MWe for factory fabrication and modular deployment. The core insight: build them in factories like airplanes instead of constructing them on-site like buildings. This should reduce cost and construction risk. NuScale and GE Vernova are the primary US competitors in this category, though NuScale's first project (UAMPS) was cancelled due to cost escalation.

Microreactors are the smallest class of nuclear technology — typically 1-20 MWe, designed to be transported on a single truck, deployed without heavy construction equipment, and operated remotely with minimal staffing. They target markets that large reactors fundamentally cannot serve: Arctic research stations, military forward operating bases, remote mining operations, and increasingly, data centers requiring reliable off-grid power. Oklo's Aurora is the leading US design, followed by Radiant and Last Energy.