Depleted uranium that was left behind in Hawai'i in the 1960s came from a recoilless rifle capable of firing a 76-pound nuclear bomb, the Pentagon confirmed for the first time yesterday.

The Army told The Advertiser that the rifle's "spotting rounds," which are fired in order to aim the trajectory of the nuclear device, were used at Schofield Barracks and possibly at Makua Military Reservation and Pohakuloa Training Area on the Big Island.

There is no evidence, however, that the fission bomb warhead itself was ever fired here, and it's unclear if it was ever stored in Hawai'i. The warhead had the strength of two to four times the explosive power that destroyed an Oklahoma City federal building in 1995.

The aiming rounds of the weapon left behind depleted uranium, and the military this summer is going to conduct radiological testing at Schofield, Makua and Pohakuloa for traces of the heavy metal, an Army official at the Pentagon said. The official requested to be identified as a "U.S. Army spokesman."

COLD WAR GAMBIT

The weapon was known as a "Davy Crockett" and featured either a 120 mm or 155 mm recoilless rifle that fired a fission bomb with a yield of .01 kilotons, equivalent to 10 tons of TNT.

Army statements confirm a link in Hawai'i to the smallest and lightest fission bomb ever fielded by the U.S. — a weapon that experts say was a desperate Cold War gambit to be used in fighting against Soviet or Chinese forces.

The result for Hawai'i is residual depleted uranium that today is the source of extreme controversy because of its possible health effects.

"I think it's a positive step that the Army is willing to investigate uranium at the ranges," said Kyle Kajihiro, program director for the American Friends Service Committee, an international Quaker organization that supports Native Hawaiian rights and demilitarization. "But we're going to reserve our judgment until we can see what their actual plans are because it's unclear how thorough (they are) and whether it will be adequate."

RANGE SURVEYS

The Army confirmed in January 2006 that 15 tail assemblies from spotting rounds made of D-38 uranium alloy were found by contractors clearing a range of unexploded ordnance at Schofield. At the time, the service said they were from an obsolete weapon system.

The Pentagon yesterday said additional depleted uranium fragments were identified near the initial find. The Schofield range is the only known location for the spotting rounds, the Army said, but this summer it will also survey ranges "with appropriate characteristics to have been used with the Davy Crockett on Makua and PTA."

"We do not expect to find any fragments," the Army said in e-mailed responses to The Advertiser, "but (we) need to verify that they do not exist on these ranges."

The Army said it will conduct surveys with sensitive radiation detectors capable of finding depleted uranium in the environment. Additional soil and water samples will be collected and sent for laboratory analysis as required, the service said.

A contract for those services still is being negotiated. Asked what has to be done to clean up any depleted uranium sites, the Army said, "We don't know yet. We need to do the initial scoping surveys to determine the extent of the (depleted uranium) residue."

ARMOR-PENETRATING

A Nuclear Regulatory Commission license is required to fire depleted uranium, or DU, rounds in the United States. The Army does not fire DU rounds from its Stryker vehicles in Hawai'i, it said, and does not intend to seek such a permit.

However, the Army said recently declassified records indicate depleted uranium spotter rounds were used in Hawai'i between 1961 and 1968, and may have been licensed. Additionally, the Army said it may have to apply for an NRC license for the purpose of cleanup.

Depleted uranium is used in some weapons systems because of its armor-penetrating capabilities. Produced in the reprocessing of spent nuclear reactor fuel, depleted uranium, with about twice the density of lead, has about 60 percent of the radioactivity of natural uranium, according to the World Health Organization.

A 1971 National Academy of Sciences report states that the M-101 spotter round for the Davy Crockett weapon system, fired from a gun fixed beneath the larger recoilless rifle, was used to simulate the trajectory of the physically larger nuclear bomb.

Asked yesterday if Davy Crockett warheads were stored in Hawai'i, Schofield Barracks officials referred questions back to the Pentagon.

'EXPERIMENTAL' WEAPON

Nuclear weapons historically had been stored in Hawai'i for possible bomber aircraft and ship missions.

Michael Pavelec, program chairman for diplomacy and military studies at Hawai'i Pacific University, doubts the Davy Crockett warheads were ever kept here, even with the spotter rounds being fired. Between 1956 and 1963, 2,100 of the bombs were produced, according to the Brookings Institution.

The bombs could be fired up to three miles but likely would have irradiated the soldiers using them. Then-Attorney General Robert F. Kennedy witnessed a test fire and detonation of a Davy Crockett in Nevada in 1962.

"These were completely experimental, but they were thinking about using tactical nuclear weapons on the western European battlefront against a potential Soviet aggression across western Germany," Pavelec said. "We were worried about hundreds and hundreds of thousands, if not millions, of either Red Army or Red Chinese, and the only way you could deal with that, they thought in the Cold War, was with really, really big bombs."

The discovery of depleted uranium in Hawai'i and its effects on U.S. troops exposed to it are part of a growing controversy over the material, which some Iraq war veterans believe is the cause of a variety of ailments.

The World Health Organization said inhaled uranium particles may lead to irradiation damage of the lung. Measurements at sites where depleted uranium munitions were used indicate only localized contamination within a few yards of the impact site, the organization said.

CAUSE FOR CONCERN?

In Hawai'i, a bill that would mandate regular testing for depleted uranium at Schofield Barracks was unsuccessful this past legislative session.

"We should be concerned. DU has the potential to really harm the public's health," said Marti Townsend, who's with Kahea, a Hawaiian and environmental group. "But we don't know anything yet. And that's the problem. We need an independent assessment of the contamination in Hawai'i."

With that, she said, an informed decision can be made about what steps need to be taken to protect the public's health.

Russell Takata, program manager for the state Health Department's Noise, Radiation and Indoor Air Quality Branch, said he hasn't detected unusual radiation levels.

"It's not like they are using the penetrating rounds here," Takata said, "and this is old stuff, very restricted, apparently small amounts, and I can't find it with my meter."

Reach William Cole at wcole@honoluluadvertiser.com.