Pictures From the Week in Business

Working on the design of a nuclear reactor at TerraPower, a start-up firm in Bellevue, Wash. Dozens of engineers, physicists and nuclear experts are chasing a radical dream of Bill Gates to build a new kind of reactor that would be fueled by today’s nuclear waste, supply all the electricity in the United States for the next 800 years and, possibly, cut the risk of nuclear weapons proliferation around the world.