IDAHO FALLS, Idaho — Inside the Transient Reactor Test Facility, a towering, windowless gray block surrounded by barbed wire, researchers are about to embark on a mission to solve one of humanity's greatest problems with a tiny device.

Next year, they will begin construction on the MARVEL reactor. MARVEL stands for Microreactor Applications Research Validation and EvaLuation. It's a first-of-a-kind nuclear power generator, cooled with liquid metal and producing 100 kilowatts of energy. By 2024, researchers expect MARVEL will be the zero-emissions engine of the world's first nuclear microgrid here at Idaho National Laboratory (INL).