Hyperion Power Generation, Santa Fe, N.M., has agreed to build a prototype nuclear mini reactor at the U.S. Energy Dept.’s Savannah River site in Aiken, S.C., officials said on Sept. 9. It signed a memorandum of understanding with the Savannah River National Laboratory to build what officials say would be the first of several small demonstration reactors at the site. Hyperion is developing a 25-MW fast-neutron reactor that uses uranium nitride fuel and lead bismuth eutectic coolant. The operational prototype should be built by 2017 or 2018, says a DOE site spokesman. The demo reactor, with a current cost estimate of $50 million, will not connect to the grid but will produce electricity for site use, he adds. It will be funded largely through private sources, says Deborah Blackwell, a Hyperion vice president. Savannah River site officials also are talking with several other companies about building reactor prototypes there, according to the spokesman. He says all designs will use “plutonium, high-enriched uranium and spent fuel,” which means that light- water models will be excluded.