NY Times, March 25-
Chinese engineers are building pebble-bed reactors that use fuel spheres ('pebbles'). Amassing these pebbles inside the reactor creates nuclear fission, which heats a gas. The gas in turn heats water into steam, driving a turbine. The reactor core consists of 420,000 of these fuel spheres, and every 15 seconds one is removed and replaced by another one. Experts say these reactors offer a safer nuclear alternative.
Each fuel sphere contains c. 12,000 uranium-laden 'microspheres'.
A schematic diagram of the reactor is shown in the NY Times article.
Graphite bricks around the core act as a reflector to enhance the reaction. Helium gas passes between the spheres, absorbing their heat.
Heat exchanger- Helium exiting the reactor goes into a cylinder with pipes of hot gas and pipes of water. The gas heats the water into steam that is sent to a turbine, producing electricity. The helium is cooled by the water and recirculated.

http://www.nytimes.com/interactive/2011/03/25/business/energyy-environment/20110325-chinanuke.html