The Navy said Friday one of its nuclear-powered submarines leaked minimally radioactive water while traveling to Japan, Guam and Hawaii over several months. The total amount of radioactivity released into the environment from the USS Houston at each stop was less than one half a microcurie, US Pacific Fleet spokesman Capt. Scott Gureck said. That was a negligible amount, equivalent to the radioactivity of a 50-pound (23-kilogram) bag of fertilizer, he said. The Navy discovered the leak July 17 when a gallon of water spilled from a valve while the submarine was in dry dock for routine maintenance at Pearl Harbor in Hawaii.