Nuke batteries get more practical.

A thimbleful of some radioactive isotopes could theoretically run a cardiac pacemaker or a sensor on a space probe for decades. However, no one has ever come up with a practical nuclear battery (SN: 8/24//02, p. 125).

Now, a team of industry and university researchers has demonstrated a tritiumfueled battery with 10 times the efficiency of earlier designs. To perform that feat, the researchers riddled a silicon chip with more than 100 million deep, narrow wells and filled them with tritium gas. When a tritium atom in a well decays, it spits out an energetic electron. Because of the well's depth, that electron rarely escapes. Instead, it plunges into a specially treated layer of the well's wall, unleashing other electrons that contribute to an electric current.

Current designs using flat silicon surfaces fail to capture about 90 percent of the tritium-emitted electrons, notes Philippe M. Fauchet of the University of Rochester, one of the new battery's developers. The well design might also improve the efficiency of solar-energy cells, he and his colleagues report in the May 13 Advanced Materials.

Despite its greater efficiency, the prototype tritium battery is too weak for practical use. To cram in more tritium and so boost the battery's electric output, the team plans to blend the gas into a polymer that will line the wells.

By immobilizing the radioactive material, this redesign also will help protect users notes Larry L. Gadeken of BetaBatt in Houston, a company that Gadeken founded to commercialize the new technology. He adds that the company plans to package commercial versions of the battery in sealed canisters.