An American nuclear-powered submarine may have leaked a small amount of radiation as it stopped by Japan in the spring and was then deployed throughout the Pacific Ocean, the Japanese government said Saturday. The Japanese government said that it was informed Friday by the United States Navy that the submarine, the Houston, might have discharged an amount of radiation that was too small to be considered harmful. The chief government spokesman, Nobutaka Machimura, said in a news conference that the radioactive amount - estimated at less than half a microcurie - was too insignificant to “affect the human body or the environment.” The submarine spent a week in March in Sasebo, in western Japan, before cruising to Guam and then Hawaii, where the leak was discovered during an inspection late last month, the Japanese government said.