PENGOLAHAN URANIUM
Sulistyani, M.Si.
Pengolahan uranium alam
• Proses konsentrasi, konsentrat uranium disebut yellow cake.
• Proses pem urnian, hingga m encapai kem urnian 99,9%.
Mining
•
Uranium ore is usually
located aerially;
core
sam ples are then
drilled
and analyzed by
geologists. The
uranium ore is extracted by m eans of drilling and
blasting. Mines can be in either open pits or
underground. Uranium concentrations are a
sm all percentage of the rock that is m ined, so
tons of tailings waste are generated by the
Milling & Leaching
•The ore is first crushed into sm aller bits, then it is sent through a ball m ill where it is crushed into a fine powder. The fine ore is m ixed with water, thickened, and then put into leaching tanks where 90 % of the uranium ore is leached out with sulfuric acid. Next the uranium ore is separated from the depleted ore in a m ultistage
washing system . The depleted ore is then neutralized with lim e and put into a
Yellowcake
•
Meanwhile, the uranium
solution is filtered, and then
goes through a solvent
extraction process that includes
kerosene and am m onia to
purify the uranium solution.
After purification the uranium
is put into precipitation tanks—
the result is a product
Transport at ion
•
In the final processes the
yellow cake is heated to
8 0 0
˚Celcius which makes a
dark green powder which is
98 % U
3O
8.
The dark green
powder is put into 20 0 liter
drum s and loaded into
shipping containers and are
shipped overseas to fuel
Conversion
• gas form of UF6. This is called To enrich uranium it m ust be in theconversion. The conversion diagram shown here is from Honeywell. First the yellow cake is converted to uranium dioxide through a heating process (this step was also m entioned in the m ining process). Then anhydrous hydrofluoric acid is used to m ake UF4. Next the UF4 is m ixed with fluorine gas to m ake
Enrichment
• Uranium enrichm ent increases the am ount of U235 in
com parison to U238 . Dom estic power plants use a m ixture that is 3-5% U235, while “highly enriched uranium ” is generally
used for weapons, som e research facilities, and naval reactors. Dom estic reactors usually require fuel in the form of uranium dioxide and weapons use the enriched m ix in the form of a m etal. The conversion and enrichm ent process is very
dangerous because not only is the uranium hexafluoride radioactive, it is also chem ically toxic. In addition, if the
uranium hexafluoride com es in contact with m oisture it will release another very toxic chem ical called hydrofluoric acid.
There have been num erous accidents during the conversion and enrichm ent process. Depleted uranium is the waste that is
Fuel Fabricat ion
•After being enriched, the UF6 is taken to a fuel
fabrication facility that
presses the powder into sm all pellets. The pellets are put into long tubes. These tubes are called fuel rods. A fuel assem bly is a cluster of these sealed rods. Fuel assem blies go in the core of the nuclear reactor. It takes
approxim ately 25 tonnes of fuel to power one 10 0 0 MWe reactor per year. The picture
