What is the Nuclear Fuel Cycle?
Nuclear Fuel Cycle is an array of an industrial process which includes a production of electricity from uranium in nuclear reactors. It can be defined as various activities that are related to generating electricity from nuclear reactions.
Nuclear fuel cycle also termed as nuclear chain reaction comprises a front end, service period and back end. The front end consists of steps that are necessary for preparation of fuel, service period involves steps in which fuel is utilized during the time span of a nuclear reactor, and back end comprises of steps that are essential for managing, conversion or disposal of used fuels.
If used fuel is not converted for reuse than the process is defined as open fuel cycle. If used fuel is converted for reuse than the process is described as closed fuel cycle. Let’s consider uranium. It is placed in a reactor for an average of three years to generate electricity. Once the electricity is produced, used fuel further undergoes various steps that are mentioned above.
Uranium is found in rocks, rivers, sea water and in most of the solids. It is one most slightly radioactive metal. In most of the places in the world, the concentration of this metal is adequately high in the ground. They are extracted and used as a nuclear fuel.
Two methods are used to recover uranium ore, evacuation, and situ techniques. Evacuation may be open pit mining. The Situ process involves oxygenated ground water that is circulated through the pores of an orebody to soften uranium oxide and to bring it to the surface. The convention mill is used to restore uranium oxide from a solution.
It is carried out near to the site of a uranium mine. A majority of mining facilities involves a mill; wherein a single mill can process ores from several mines. Milling involves a production of uranium oxide concentration that is carried out from the mill.
Conversion of Uranium
It includes the conversion of uranium oxide into uranium hexafluoride. This product only consists of natural uranium, not the enriched product. Uranium hexafluoride is converted in gaseous form at a moderate temperature of 57 °C.
The concentration of U-235 is less than a requirement to sustain a nuclear chain reaction. Hence it has to be enriched in fissionable isotopes and it is carried through two processes namely low-enriched uranium and simply depleted uranium.
In this process, uranium dioxide is converted into pellet form. The pellets are fired at a very high temperature to form enriched uranium and then undergo a grinding process. These pellets are connected through metal tubes organized in a fuel assembly to assure consistency in the fuel.
The core of a reactor is made up of several hundreds of fuel assemblies. U – 235 isotopes split producing an excess of heat. This process is known as a chain reaction and it entirely depends upon the type of moderator namely graphite or water.
In some countries depending upon the policies, used fuels may be shipped into central storage facilities.