Antares has announced that its small modular nuclear reactor, the Mark 0, has reached criticality for the first time. This test validates the company's modeling of physical conditions inside its reactors and provides crucial safety data for licensing.
The Antares design uses TRISO fuel pellets, which are encased in a graphite sheath to contain fission products and slow neutrons. The reactor employs sodium as a coolant, transferring heat to pressurized nitrogen that drives a turbine in a closed Brayton cycle-a design that minimizes radioactive risk.
The Mark 0 is not yet connected to power generation; full-system tests including electrical output are planned for next year. Antares is working with the Department of Defense's Project Pele program to develop a mobile nuclear reactor and has also received support from NASA.