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Details of Depleted uranium

Depleted Uranium (DU) is uranium remaining after removal of the isotope uranium-235. It is primarily composed of the isotope uranium-238. In the past it was called by the names Q-metal, depletalloy, and D-38, but these have fallen into disuse. Since depleted uranium contains less than one third as much uranium-235 and uranium-234 as natural uranium, it is weakly radioactive and an external radiation dose from depleted uranium is about 60% of that from the same mass of uranium with a natural isotopic ratio.

At standard temperature and pressure (STP) it is a very dense metal solid. Due to its high density the main uses of depleted uranium include counterweights in aircraft, radiation shields in medical radiation therapy machines and containers for the transport of radioactive materials. The military uses depleted uranium for defensive armor plate and its pyrophoricity has made it a valued component in other military applications, particularly in the form of armour-piercing projectiles.

Its use in ammunition is controversial because of its release into the environment. Besides its residual radioactivity, U-238 is a heavy metal whose compounds are known from laboratory studies to be toxic to mammals. However, there has never been a definitive toxicological link established in humans and it is believed that low and moderate exposures to depleted uranium pose little if any toxicological threat.

Depleted uranium storage yard.

Sources

Depleted uranium is produced as a byproduct during the process of forming enriched uranium from natural uranium. Enriched uranium is used in nuclear reactors. When the majority of fissile radioactive isotopes of uranium are removed from natural uranium, what remains is called depleted uranium. Another, less common, source of Depleted Uranium is reprocessed spent reactor fuel. DU created by enrichment can be distinguished from DU created in a reactor by the percentage of uranium-236,[6] produced by neutron capture from uranium-235 in nuclear reactors, present in the material.

DU is considered both a toxic and radioactive hazard that requires long term storage as low level nuclear waste. DU is relatively expensive to store but relatively inexpensive to produce or obtain. Generally the only real costs are those associated with conversion of uranium hexafluoride (UF₆) to metal. DU is extremely dense, 67% denser than lead, only slightly less than tungsten and gold, and just 16% less dense than osmium or iridium, the densest naturally occurring substances known. Its low cost makes it attractive for a variety of industrial and military uses. However, the material is prone to corrosion and small particles are pyrophoric. [7]

History

Depleted uranium was first stored in stockpiles in the 1940s when the U.S. and USSR began their nuclear weapons and nuclear power programs. While it is possible to design civilian power reactors with unenriched fuel, only about 10% of reactors ever built utilize that technology, and both nuclear weapons production and naval reactors require the concentrated isotope. Originally, DU was conserved in the hope that more efficient enrichment techniques would allow further extraction of the fissile isotope; however, those hopes have not materialized.

In the 1970s, The Pentagon reported that the Soviet military had developed armor plating for Warsaw Pact tanks that NATO ammunition couldn't penetrate. The Pentagon began searching for material to make denser bullets. After testing various metals, ordnance researchers settled on depleted uranium. DU was useful in ammunition not only because of its unique physical properties and effectiveness, but also because it was cheap and readily available. Tungsten, the only other candidate, had to be sourced from China. With DU stockpiles estimated to be more than 500,000 tons, the financial burden of housing this amount of low-level radioactive waste was very apparent. It was therefore more economical to use depleted uranium rather than storing it. Thus, from the late 1970s, the U.S., the Soviet Union, Britain and France, began converting their stockpiles of depleted uranium into kinetic energy penetrators.

Photographic evidence of destroyed equipment suggests that DU was first used during the 1973 Arab-Israeli war. Various written reports cite information that was obtained as a consequence of that use. However, while clearing the decades-old Hawaii Stryker firing range, workers have found depleted uranium ammunition from the 1960s.^{[citation needed]}

The U.S. military used DU shells in the 1991 Gulf War, Bosnia war[8], Serbia bombing, and the 2003 Iraq War.