Money, size and speed
While the U.S. has the most active nuclear power plants, China is king of new projects.
Despite breaking ground on its first reactor nearly four decades after the U.S. pioneered the tech, China's now building far more fission power plants than any other country.
China entered the fusion race in the early 2000s, about 50 years after the U.S., when it joined more than 30 nations to collaborate on the International Thermonuclear Experimental Reactor fusion megaproject in France. But ITER has since hit major delays.
The race is on between individual nations, but the U.S. private sector remains in the lead. Of the $8 billion in global private fusion investment, $6 billion is in the U.S., according to the FIA.