Reuters: Kitty litter used to absorb liquid in radioactive debris may have triggered a chemical reaction that caused a radiation leak at a below-ground U.S. nuclear waste storage site in New Mexico, a state environmental official said on Tuesday. The waste disposal site, where drums of plutonium-tainted refuse from nuclear weapons factories and laboratories are buried in salt caverns 2,100 feet (640 meters) underground, has been shut down since unsafe radiation levels were first detected there on Feb. 14....