X-Energy is building a Gen IV reactor it claims can't melt down

X-energy, a Maryland-based company, is developing the Xe-100, a Generation IV pebble-bed, high-temperature gas-cooled nuclear reactor designed to be meltdown-proof. Unlike conventional reactors that use long fuel rods submerged in water, the Xe-100’s core contains thousands of graphite spheres ("pebbles") filled with TRISO fuel particles—uranium kernels coated with multiple ceramic and carbon layers that trap radioactive materials even at extreme temperatures. This design allows the reactor to operate safely near urban or industrial areas and eliminates the need for active cooling systems, as spent fuel can be stored on-site in dry casks without interim cooling. The Xe-100 uses helium gas as a coolant, which is chemically inert and does not become radioactive, avoiding the instability risks associated with water-based cooling systems. The reactor dissipates heat passively through conduction and convection, maintaining fuel integrity even if helium coolant is lost. Each 80 MWe module is fully modular and can be scaled up to a 320 M