Chief of the Materials Decommissioning Branch
The Davy Crockett weapons system – a Cold War-era recoilless rifle – never actually saw battle. But there are remnants of it at several former training sites around the country, including two in Hawaii. How does that involve the NRC? A part of this system, the spotting round, contained depleted uranium (DU). The NRC is now reviewing the Army’s application to possess and manage these spotting rounds in Hawaii.
The Atomic Energy Commission, the NRC’s predecessor, gave the Army a license to fabricate and distribute the spotting rounds. These low-speed projectiles helped to ensure accurate targeting. They emitted a puff a white smoke on impact. They did not explode, but they made it possible to see if aiming adjustments were needed.
In 2005, the Army found tail assemblies from the spotting rounds at the Schofield Barracks on Oahu. That discovery prompted a review of all sites where the Army trained with the system. The Army found DU at other sites, including the Pohakuloa Training Area on the big island of Hawaii. The Army has enough DU at these sites that, under NRC regulations, it is required to have a possession license. The Army applied for an NRC license in November 2008.
Natural uranium is made up of three “isotopes”—forms with different numbers of neutrons and distinct physical properties: U-234, U-235 and U-238. “Depleted” uranium has had U-234 and U-235 removed, increasing the percentage of U-238. Only slightly radioactive, DU can be toxic to the kidneys if ingested, such as by inhaling dust or drinking contaminated water. DU is about twice as dense as lead, making it useful in commercial and military applications.
An Army information booklet said the DU is in large fragments, not small dust particles. It is on operational ranges that are not accessible to the public. Data the Army collected and analyzed show there is no immediate health risk to people who work at the ranges or live nearby. The high density and large fragment size mean the DU cannot easily become airborne or move off-site.
The NRC asked the Army to provide plans for environmental radiation monitoring and security. The Army initially provided two plans that could apply to any of the sites where it used Davy Crockett spotting rounds. It later provided specific plans for the two sites in Hawaii.
The NRC is continuing to work with the Army to issue a license. As an NRC licensee, the Army must follow NRC regulations and standards for protecting the public and the environment. These may include monitoring radiation in the air and plants and further controlling access to the sites. The NRC will oversee that monitoring through periodic inspections and reviews. The Army will be able to amend its license to add other sites where it has found DU from the Davy Crockett system. The license and the Army’s monitoring and access control programs will support future site cleanup.
More information on DU is available on the Heath Physics Society’s website.