Sunday, December 27, 2009

Depleted uranium / Sources of pollution

Depleted uranium

Munitions using depleted uranium (DU) were used during the Gulf War in 1991 and in the conflicts during the 1990s surrounding the break-up of Yugoslavia. The risks of harm to military personnel on a battlefield should be put in context of the other self­evident risks, but the use of depleted uranium ordnance has raised concerns about subsequent health consequences, both to service personnel and to the public after the conflict.

As has already been discussed, uranium occurs naturally in the environment. It is widely dispersed in the Earth's crust, and in fresh water and sea water. As a result, we are all exposed to uranium isotopes and their decay products, and there are wide variations in doses received depending on local circumstances. DU is a by-product of the uranium fuel cycle where natural uranium is enriched to provide suitable fuel for nuclear power. It is called depleted because it has had some of its uranium-235 isotope removed. A large fraction of decay products of the uranium isotopes is removed during the fuel enrichment process.

Depleted uranium in munitions is in a concentrated metallic form, and there are under­standable concerns about elevated levels in the environment due to spent munitions. There are also worries about people handling intact depleted uranium metal. Assess­ments of dose to military personnel who entered a tank shortly after it was hit by a DU weapon indicate possible doses of up to a few tens of mSv from inhalation of vapours and dust. In contrast, doses to people exposed some time afterwards to resuspended dust in the same local environment are likely to be a thousand times less, typically a few tens of µSv. Contact doses when handling bare DU metal are approximately 2.5 mSv/h, primarily from beta radiation, which is not penetrating and so affects only the skin. Even so, the collection of bare DU munitions needs to be discouraged and, if possible, avoided completely.

Doses from depleted uranium are, therefore, real and, in some circumstances, they could be appreciable for military personnel. Doses to people in the post-conflict phase are likely to be much lower and should be relatively easy to avoid.

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