Depleted uranium is a mixture of uranium isotopes with reduced
concentration of unstable isotope uranium-235, whose decay energy
is used in uranium fuel or warheads. The depleted uranium is formed
as a result of processing (enriching) of natural uranium or as a
result of processing of the irradiated nuclear fuel. All depleted
uranium is stored in a hexafluoride.
To compare: natural (produced) uranium contains, as a rule, 0.7%
of uranium-235. Almost all the rest is uranium 238 isotope. For
using uranium fuel for nuclear power plants it is neccesary to
enrich uranium-235 up to 5%. Uranium contents for nuclear warheads
are enriched with uranium-235, starting from 20%.
Uranium hexafluoride is a salt of hexavalent uranium and fluoric
acid. At the normal pressure and temperature +56,4С ˚ transforms
from a firm condition in gaseous, passing a liquid phase. This
active chemical easily reacts with water, including an atmospheric
moisture. While interacting with water fluoric acid is formed.
Waste uranium hexafluoride (WUH) is poisonous. Inside a body, it
causes radiation impact as an alpha emitter. Fluoric acid is not
less dangerous, and possesses irritating action on skin and mucous
membranes of eyes, causes painful burns. Acid steam inhalation
attaks lungs and during the time. Sharp and chronic poisonings with
change of blood and blood-forming organs, alimentary organs, a
hypostasis of lungs are possible
Waste uranium hexafluoride (WUH) usage. In the world huge stocks
of WUH are saved up. Because of impossibility of wide commercial
application countries are compelled to store or process a dangerous
waste. For example, in the U.S. there are 740 thousand tons of
waste uranium hexafluoride. [1]. In Russia the total amount of
waste uranium hexafluoride is hundreds of thousands of tons [7].
The stocks of WUH are growing constantly.
Till now in the world the industrial scheme of full recycling of
WUH is not developed. From the point of view of safety, it is
accepted to translate WUH in deplated oxide uranium which is a firm
substance. Fluorine which is used for production of the fluoric
acid applied in the industry emits. Oxide uranium as the kind of a
radioactive waste must be buried or can be used in fast neutrons
reactors for a plutonium operating. There are also other commercial
ways of deplated oxide uranium usage, but they don't have wide
application.
The decision about a method to utilize uranium depends on if a
country considers depleted uranium as radioactive waste or as
material for further use.
For example, the U.S. depleted uranium had been till recently
regarded as material for further use. However in 2005 this was
changed and now depleted uranium oxide can be disposed in the U.S
[1].
In the Russian Federation heads of the Russian Atomic Energy
Agency regard waste uranium hexafluoride as valuable materials not
liable to disposal. According to [3], operations have been started
to construct a plant to convert waste uranium hexafluoride to the
safe form - uranium oxide. Produced uranium oxides are projected
for a long term storage and are going to be used in future
technologies of fast neutron reactors [4]. In Russia there are no
established technologies to convert WUH to uranium oxide [4,5].