Sunday, May 26

Uranium Nuclear Fuel

Introduction to Uranium nuclear fuel:

The basic fuel materials for the generation of nuclear power are the elements Uranium and Thorium. Of these, Uranium has played a major rule. Uranium is by no means a rare substance and it has been estimated to be around 4ppm of the earth’s crust. In fact, Uranium is more abundant  than relatively familiar elements such us silver, mercury, bismuth and cadmium. Although the estimated total weight of Uranium in the earth’s crust is 1014 metric tons yet most deposits are of such a low grade that the extraction of the metal would appear to be uneconomical. Uranium is extracted from the ores containing primary minerals Pitchblende and Uraninite (UO2  and  U3O8). Uranium is solvent extracted to finally produce ‘yellow cake’ containing 75% to 85% of  U3O8.  This is subjected to further treatment leading to almost pure Hexafluoride (UF6) as a product.  Uranium dioxide (UO2), Uranium metal, Uranium carbide and Uranium nitride are some of the final products that will be used as reactor fuel.Please express your views of this topic Definition of Torque by commenting on blog.

Uranium metal fuel:

Metallic Uranium was used as a fuel in most of the earlier nuclear reactors, largely because it provides the maximum number of Uranium atoms per unit volume. Since it has poor mechanical properties and great susceptibility to radiation damage, Uranium metal fuel  is not used in power reactors in many countries. It was used as a fuel in the older gas-cooled reactors.

Uranium dioxide nuclear fuel:

Uranium dioxide (UO2) , a ceramic which is the most common fuel material in commercial power reactors, has the advantages of high-temperature, stability and adequate resistance to radiation. It also has a high melting point of 2865oC and is chemically inert to attack by hot water. It is this property which makes it attractive for use in water- cooled reactors, where the consequences of a cladding failure could be catastrophic if the fuel material reacted readily with the water at the existing high temperature. Another beneficial property of Uranium dioxide is its ability to retain a large proportion of the fission gases provided the temperature does not exceed about 1000oC. The major disadvantage of Uranium dioxide as a fuel material is its low thermal conductivity, although this is partially offset by the fact that very high temperatures are permissible in the centre of the fuel element.

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