A nuclear power plant is not much different from a conventional power plant except for the manner in which heat is generated using nuclear reactions. We will study one very important component of nuclear power plants here, namely the fuel rods used in the reactor core, and the nuclear fuel cycle.
Fuel is needed for any energy producing process and refers to the material which is either burned or altered in order to produce energy. Burning takes place in case of chemical reactions, whilst alternation takes place in the nuclear reactions. Both these processes are exothermic but the latter leads to much more release of thermal energy as compared to chemical reactions for similar quantities of fuel. No doubt fuel rods top the list in the components of nuclear power plants for there would be no "fire" without the fuel.
What is a Fissile Nuclide?
As you must have surely guessed, fissile has something to do with fission and you are right about this. A fissile material is that which attains fission when hit by a neutron of any energy level. The commonly known fissile nuclides are isotopes of Uranium and Plutonium namely U-233, U-235, Pu-239 and Pu-241.
What is a Fertile Nuclide?
Whereas a fissile nuclide can achieve fission with any neutron, a fertile nuclide is one which requires neutrons of more than a certain level of energy to achieve the same usually in the range of 1-MeV. If you are wondering why the name fertile is given to a seemingly infertile nucleus, let me explain the reason to you. Actually a fertile nuclide becomes fissile upon absorption of the appropriate neutron hence the name fertile. We all know fertile nuclide include the U-235 isotope of Uranium and Thorium Th-232.
Shape of Fuel Used
Fuel is usually placed within the reactor core in the form of fuel rods which are fabricated and placed within the reactor in such a manner so that it leads to a uniform production of heat within the reactor. There are two types of reactors based on the manner in which the fuel and moderator are placed within the core as follows.
- The homogenous reactor is one in which the fuel and moderator are mixed to form a uniform mixture which is then placed in the form of rods and plates inside the reactor core.
- A heterogeneous reactor on the other hands has pure fuel in the form of rods or plates while the moderator surrounds the fuel elements separately. In this case the fuel rods are often clad with different materials including Aluminium, Stainless Steel or Zirconium which help to prevent oxidation of Uranium.
The Fuel Cycle
The fuel cycle with regards to the nuclear power plant refers to the total process of preparation of fuel, burning of fuel and final disposal. If the fuel from the last stage is recycled to be used again in the nuclear reactor, it is known as a closed fuel cycle otherwise it is known as open fuel cycle. Of course in the former case, fuel is not thrown or dumped away at any random place but is placed and packaged properly in order to prevent contamination of the biosphere.
We learnt a few basic things about the fuels used in nuclear power plants in this article. These fuel materials certainly act as the backbone of nuclear industry and will help to achieve a powerful source of viable alternative energy for our future energy requirements.