Nuclear Fuel Cycle

There are two categories for fuel.

Fissile: These elements are fissionable:


Fuel Cycle 1

• U235 : It is the only natural fissile fuel can be found in environment

• U233: It comes from Th232

• Pu239: It comes from U238


Fertile: These elements by absorbing a neutron, transforms to fissionable materials

• U238

• Th232

     Nuclear fuel cycle starts from obtaining uranium ore from mine and finishes at reprocessing stage.


Fuel Cycle 2

Fuel Cycle 3

     On every stage, uranium changes its form by chemically or physically.



Fuel Cycle 4

Mining

     In this stage, ore is extracted from mine and sent to milling.


Milling

     Uranium ore is milled to yellow cake (U3O8).


Fuel Cycle 5



Conversion

      Yellow cake is purified and conversed to UF6. UF6 is only stable gaseous for of uranium and it can be easily enriched. It is sent to enrichment unless it will go to CANDU. If fuel will be for CANDU, it will be conversed to UO2.

Enrichment

      In this stage, UF6 is enriched to desired enrichment. Then it is conversed to UO2 and sent to fabrication. UO2 is in ceramical form and it can endure high temperatures. Depleted uranium is obtained as extract and it is storaged for using in another stages or reactors.

Fabrication

     In fabrication stage, UO2 powders are comsupssed and shaped as pellets. Rods and assemblies are also formed. These pellets are adjusted in these rods and fuel rods are done. Fuel assemblies and rods are sent to reactor.


Fuel Cycle 6

Fuel Cycle 7



Fuel Storage

     When the fuel rods are completed their function, they are replaced with new ones. The used fuel rods are called as spent fuels and they need to be cooled down and shielded since they are highly radioactive and they generate decay heat. Usually, they are placed in storage pool near reactor for a while. After that, they are either reprocess or left in pools.

Fuel Cycle 8

Reprocess

     Spent fuel is sent to reprocess sites to separate uranium, plutonium and transuranic elements with each other. Several physical and chemical methods are applied to spent fuel. Recovered uranium can be sent to enrichment stage again or can be blended with obtained plutonium and MOX fuels can be produced. Depleted uranium from enrichment stage can be used for production of MOX fuel. Fission products are vitrified and buried to proper depth under ground.