China's bragging about being the first to build a next-generation nuclear reactor. Here's how it compares to reactors in countries like the US, Japan, and Russia.

• China on Wednesday said the Shidaowan nuclear reactor is officially contributing to the power grid.
• While less powerful than foreign plants, it's the world's first reactor that uses helium, not water.
• Nuclear plants often use billions of gallons of water per day, a problem for water-starved China.

China on Wednesday announced that it's started commercial operations at the world's first next-generation nuclear reactor.