6. Properties of uranium

Uranium is a hard, dense, malleable, ductile, silver-white, radioactive metal. Uranium metal has very high density. When finely divided, it can react with cold water. In air it is coated by uranium oxide, tarnishing rapidly. It is attacked by steam and acids. Uranium can form solids solutions and intermetallic compounds with many of the metals.

Consumption

Uranium gained importance with the development of practical uses of nuclear energy. Depleted uranium is used as shelding to protect tanks, and also in bullets and missiles. The first atomic bomb used in warfare was an uranium bomb. This bomb contained enough of the uramium-235 isotope to start a runaway chain reaction

The main use of uranium in the civilian sector is to fuel commercial nuclear power plants. This require uranium to be enriched with the uranium-235 isotope and the chain reaction to be controlled so that the energy is released in a more manageable way.

The isotope uranium 238 is used to estimate the age of the earliest igneous rocks and for other types of radiometric dating.

Phosphate fertilizers are made from material typically high in uranium, so they usually contain high amounts of it.

Resources

Although uranium is radioactive, it is not particularly rare. It is widely spread throughout the environment and so it is impossible to avoid uranium. Uranium can be found naturally in the environment in very small amounts in rocks, soil, air and water. Humans add uranium metals and compounds, because they are released during mining and milling processes.

In air the uranium concentrations are very low. Even at higher than usual concentrations in air, there is so little uranium present per cubic meter that less than one atom transfers every day.

In water most of the uranium is dissolved uranium that derives from rocks and soil that the water runs over. Some of the uranium is suspended, so that the water gets a muddy texture. Only a very small part of uranium in water settles from air. The amounts of uranium in drinking water are generally very low.

Uranium is found in soils in varying concentrations that are usually very low. Humans add uranium to the soil through industrial activities.

Erosion of tailing from mines and mills may cause larger amounts of uranium to be released into the environment.

7. Fuel cycle

The nuclear fuel cycle, also called nuclear fuel chain, is the progression of nuclear fuel through a series of differing stages. It consists of steps in the front end, which are the preparation of the fuel, steps in the service period in which the fuel is used during reactor operation, and steps in the back end, which are necessary to safely manage, contain, and either reprocess or dispose of spent nuclear fuel. If spent fuel is not reprocessed, the fuel cycle is referred to as an open fuel cycle (or a once-through fuel cycle); if the spent fuel is reprocessed, it is referred to as a closed fuel cycle.

Nuclear Fuel - a substance used in nuclear reactors to carry out a nuclear chain fission reaction Get uranium nuclear fuel recycling ore. The process occurs in several stages:

For poor fields: In modern industry because of the lack of rich uranium ore used method of underground leaching ore. Advance preparation is directly under the ground. Through tubes over the field is pumped of sulfuric acid , sometimes with the addition of of trivalent iron salts. Through special tubes pump sulfuric acid solution with uranium rises to the surface. Then he directly goes to sorption, hydrometallurgical extraction

For ore deposits: using radiometric enrichment of ore and enrichment of ore. Hydrometallurgical processing - crushing, leaching, sorption or extraction of uranium extraction to obtain purified uranium U3O8 or dyuranatu sodium Na2U2O7 or ammonium dyuranatu.

The transition uranium with oxide in tetrafluoryd UF4, or with oxides directly for receiving heksafluorydu UF6, which is used to enrich uranium in isotope-235. Enrichment by gas thermal diffusion or centrifugation (separation of isotopes) UF6, enriched in the isotope 235 is converted into Dioxide of UO2, which made "pills" fuel elements or receive other compounds of uranium for the same purpose. Thorium and plutonium fuel in our time as the raw material for production nuclear fuel does not apply

When operating nuclear reactor, the fuel is not completely burned, there is process of reproduction some isotopes (Pu). In this connection, spent fuel rods sent for recycling for fuel reformation and re-use. Currently, the most widely used pyureks process (Plutonium and Uranium Recovery by EXtraction), the essence of which is as follows: fuel rods cut into pieces and dissolved in nitric acid, then purified by solution from fission products and components membrane allocate pure compounds U and Pu. Then the resulting plutonium dioxide PuO2 sent to the production of new cores, and uranium or for the manufacture of cores, or the enrichment of 235U. Recycling and regeneration of highly radioactive materials - a complex and expensive process. After extracting fuel rods from reactors can withstand for several years (typically 3-6) in special storage. Difficulties also entails recycling and disposal of waste unsuitable for regeneration. The cost of all these actions significantly affect the economic efficiency of nuclear power stations.