The Navy said a nuclear-powered submarine leaked minimally radioactive water while traveling to Japan, Guam and Hawai'i over several months.

The total radioactivity released into the environment from the USS Houston at each stop was less than one half a microcurie, U.S. Pacific Fleet spokesman Capt. Scott Gureck said.

That's a negligible amount, equal to the radioactivity of a 50-pound bag of fertilizer, he said.

The Navy discovered the leak July 17 when a gallon of water spilled on a shipyard worker's leg from a valve while the submarine was in dry dock for maintenance at Pearl Harbor.

An investigation showed water may have been slowly leaking from the valve since March as the Los Angeles-class submarine traveled around the Pacific.

Gureck said the ship is designed to leak, or "weep," a small amount of water, but the amount coming from the sub was higher than normal. Even so, he said the total leaked volume was minuscule.

The Houston is based at Apra Harbor in the U.S. territory of Guam in the Western Pacific.

It visited a U.S. naval base in Sasebo, Japan, in late March, and then stopped in Guam from late May to mid-June. The submarine sat in Pearl Harbor for about three weeks before it was dry-docked in mid-July.

Hawai'i Department of Health spokeswoman Janice Okubo says the Navy reported the leak to the department's radiation and indoor air quality branch. Authorities didn't take action because they didn't see any issue that would create a threat, she said.

Okubo said the department periodically receives such reports from the Navy, but she didn't know how often.

"The smallest thing could happen and they report it to us, which we really appreciate," Okubo said. "We of course review it and want to know corrective action has been taken."

Gureck said the Navy also alerted the Japanese government after the investigation. Japanese nuclear monitors didn't detect any unusual radioactivity in Sasebo when the submarine was there, he said.

Sasebo city official Akihiro Yoshida said the government monitoring during the submarine's port calls showed no abnormal increase of radioactivity in the area's waters.

"Still, we are rather concerned," Yoshida said.

Masahiko Goto, a lawyer representing a citizens' group opposing the George Washington's deployment in Yokosuka, sharply criticized the U.S. Navy for withholding the problem for weeks.

"They had discovered the radiation leak weeks ago and did not inform the Japanese government immediately," he said in a statement. "The U.S. Navy's handling of the accident and lack of transparency showed there is no way we can trust them."