Elements of Z ≥ 90 have fissionable isotopes, and a few are fissile, i.e., readily fission with thermal neutrons. U-235 occurs naturally, but as a small fraction (0.0071) of uranium, in certain ores. We use Pu-239 and Pu-241 as fuel in thermal and fast reactors, and in a few systems, we have used U-233. Fissile isotopes of elements heavier than uranium have to be produced in reactors, and most radionuclides heavier than Pu have shorter half-lives and many undergo spontaneous fission.SANKET HAQUE said:According to the experimental curve of Binding Energy per nucleon vs Mass no. , we have come to know that heavier nuclei having less B.E. are fissionable. We have also learned from Neutron vs Proton curve that those nuclei having N/P>1 can show radioactivity. But my question is why not all heavy nuclei are fissionable? Why we only take Uranium as our fission element?
Indeed. The longest lived isotope for which the most common decay path is fission rather than alpha or beta decay is curium 250, with total half-life of 8300 years, of which 80 % is fission.mathman said:Most nuclei that are unstable are radioactive (alpha decay, beta decay, etc.) rather than fissionable.
snorkack said:Indeed. The longest lived isotope for which the most common decay path is fission rather than alpha or beta decay is curium 250, with total half-life of 8300 years, of which 80 % is fission.
However... the lighter nuclei, from polonium to actinium, are much less stable than the nuclei on the island of stability, from thorium to curium.
Why does, e. g. radium undergo only alpha decay? Seeing how unstable radium is, why does radium not undergo fission?
Nuclear fission is a process in which the nucleus of an atom splits into two or more smaller nuclei, releasing a large amount of energy. This process occurs under specific conditions.
In order for nuclear fission to occur, there are a few conditions that must be met. The first is that the nucleus of the atom must be unstable, meaning it has excess energy. The second condition is that the nucleus must be struck by a neutron in order to start the fission process. Finally, the atom must have a large enough mass to sustain the chain reaction of splitting nuclei.
Control rods are an important part of the nuclear fission process. They are made of materials that absorb neutrons, such as boron or cadmium. By inserting or removing control rods, scientists can control the rate of the fission reaction. This is important for safety and efficiency of nuclear reactors.
The energy released in nuclear fission is harnessed through a process called nuclear chain reaction. As the nuclei of the atoms split, they release energy in the form of heat. This heat is then used to produce steam, which turns turbines and generates electricity.
Nuclear fission has several advantages, such as producing large amounts of energy without producing greenhouse gases. It is also a reliable source of energy and operates continuously. However, there are also disadvantages, including the potential for accidents and the production of radioactive waste, which can be harmful to the environment and human health if not properly managed.