Neil Johnson, a University of Miami physicist, developed this mathematical formula to predict insurgent attacks in war zones. Courtesy of Neil Johnson hide caption

itoggle caption Courtesy of Neil Johnson

Campers Mary Church and Jimmy Cong use their sense of smell to detect whether a chemical reaction has taken place. Amy Standen for NPR hide caption

itoggle caption Amy Standen for NPR

Last year, the Obama administration canceled plans to make Yucca Mountain the permanent storage site for the nation's nuclear waste. The half-built site is seen here in a file photo from 2006. Isaac Breekken/AP hide caption

itoggle caption Isaac Breekken/AP

Above-ground casks at the Diablo Canyon nuclear power plant store some of the utility's nuclear fuel. Because of a lack of a central repository, nuclear waste is piling up at individual reactor sites across the United States. Michael Mariant/AP hide caption

itoggle caption Michael Mariant/AP

A model of a storage container illustrates how used nuclear fuel will be placed in cast-iron inserts, then encapsulated in large copper cannisters and buried more than 1,500 feet down in the Swedish bedrock. Ingrid Becker/KQED hide caption

itoggle caption Ingrid Becker/KQED