Nuclear fission is a process where the nucleus of a heavy atom is split into two or more lighter nuclei, releasing a significant amount of energy. This fundamental concept in physics involves transforming matter into energy, following Einstein’s famous equation E=mc².
The Atom’s Core for Fission
Atoms consist of a central nucleus surrounded by orbiting electrons. Nuclear fission specifically involves changes within this dense nucleus, which is made up of protons and neutrons. The forces holding these particles together within the nucleus are immensely strong.
The stability of an atomic nucleus depends on the balance between these strong nuclear forces and the repulsive electrical forces between protons. For very heavy atoms, like uranium or plutonium, the large number of protons creates significant repulsive forces, making their nuclei less stable. This inherent instability is a prerequisite for fission.
Certain heavy isotopes are particularly susceptible to fission. Isotopes are atoms of the same element with the same number of protons but different numbers of neutrons. For instance, Uranium-235 (U-235) and Plutonium-239 (Pu-239) are considered “fissile” because their nuclei can be easily split when struck by a neutron. Uranium-235 is the only naturally occurring fissile isotope.
The Fission Process Explained
The process of nuclear fission typically begins when a neutron strikes the nucleus of a fissile atom, such as Uranium-235. The nucleus absorbs this incoming neutron, becoming highly unstable. For example, a U-235 nucleus absorbing a neutron transforms briefly into an excited Uranium-236 nucleus.
This newly formed, unstable nucleus then promptly splits into two or more smaller nuclei, known as fission products. This splitting releases a substantial amount of energy, primarily in the form of kinetic energy of the fission products and gamma rays. Alongside the energy, two or three additional neutrons are also emitted.
These newly released neutrons can then go on to strike other nearby fissile nuclei, initiating further fission events. This sequential process is called a nuclear chain reaction. If enough fissile material is present and the neutrons are effectively utilized, this chain reaction can become self-sustaining, leading to a continuous release of energy. The energy released from the fission of a small amount of uranium is significantly greater—millions of times more—than that produced by chemical reactions like burning fossil fuels.
Real-World Uses of Atom Splitting
The controlled chain reaction of nuclear fission is primarily harnessed for generating electricity in nuclear power plants. In these facilities, the heat produced by fission is used to boil water, creating high-pressure steam. This steam then drives turbines, which are connected to generators to produce electricity.
Beyond power generation, nuclear fission has other significant applications. Research reactors utilize the controlled fission process to produce neutrons for various scientific experiments and material studies. The process also plays a role in the production of medical isotopes. These radioactive isotopes are used in diagnostic imaging, such as PET scans, and in targeted radiation therapies for cancer treatment.