This energy is called nuclear fission energy or nuclear energy. For example, to start a fission chain reaction of U-235, the critical mass is about 10 kg.Ī huge amount of energy is released when U-235 or Pu-239 undergo a chain reaction. The minimum amount of the mass of fissionable material required to sustain a chain reaction is called its critical mass. As result, the chain reaction would break. If the sample is too small, most of the neutrons would strike the surface and escape. Its size should be large enough to capture the neutrons internally. That is the reason why, to start a chain reaction, the sample must be contain fissioned material. Most of them are lost in their surroundings. It is not necessary that all the neutrons produced in the chain reaction are used to propagate further reactions. This makes a long chain of reactions, known as, fission chain reaction. This process of propagation continues in powers of 3 like 3, 9, 27, 81, etc. These 9 electrons then undergo similar reactions until a large bulk of neutrons is produced after some consecutive reactions. When neutrons are bombarded on uranium-235, it breaks it into barium (Ba) and krypton (Kr) along with releasing three neutrons.Įach of these three neutrons strikes another uranium-235 nucleus which results in the emission of 9 neutrons. This lost mass converts into a great amount of energy that is about 2.5 million times greater than the energy produced by the same amount of coal. This mass corresponds to the binding energy of the system. This loss is about 0.2 amu per uranium atom. The above fission reactions show a minute decrease in the overall mass of products. The products that are formed as the result of fission are known as fission products.įor example, uranium 235 can undergo fission reaction in the following ways The splitting of a heavy nucleus into two or more daughter nuclei is called a fission reaction. This unstable nucleus splits into daughter nuclei and releases further neutrons and a large amount of energy. For example, uranium-235 absorbs a neutron and becomes a compound nucleus that is unstable. They observed that a heavy nucleus splits into daughter nuclei when neutrons are bombarded on it. In 1939, two scientists Hahn and Strassmann discovered fission. Nuclear reactors and atomic bomb are examples of fission reactionĬERN particle collider and hydrogen bomb are examples of fusion reaction Their products of fusion reaction are non-radioactive The products of fission reaction are radioactive Released energy can be used for further process 1000000 oCįission reactions can be controlled by control rodsįusion reaction, once started, cannot be controlled It requires extremely high temperature i.e.

Fusion vs fission