Fission reaction does not normally occur in nature Fission produces many highly radioactive particles The energy released by fission is a million times greater than that released in chemical reactions; but lower than the energy released by nuclear fusion One class of nuclear weapon is a fission bomb, also known as an atomic bomb or atom bomb. Nuclear fission is the splitting of a massive nucleus into photons in the form of gamma rays, free neutrons, and other subatomic particles.
In a typical nuclear reaction involving U and a neutron:. The energy released by fusion is three to four times greater than the energy released by fission. Extremely high energy is required to bring two or more protons close enough that nuclear forces overcome their electrostatic repulsion. Nuclear fusion is the reaction in which two or more nuclei combine together to form a new element with higher atomic number more protons in the nucleus.
On earth, the most likely fusion reaction is Deuterium—Tritium reaction. Deuterium and Tritium are both isotopes of hydrogen. In contrast, most chemical oxidation reactions such as burning coal release at most a few eV per event. So, nuclear fuel contains at least ten million times more usable energy per unit mass than does chemical fuel.
Fusion is the opposite reaction of fission. In fusion, atoms are fused together. For a fusion reaction to occur, it is necessary to bring two nuclei so close that nuclear forces become active and glue the nuclei together. It had a yield of 10 megatons MT , about times that of the fission bomb that destroyed Hiroshima.
The Soviet Union followed with a fusion device of its own in August , and a weapons race, beyond the aim of this text to discuss, continued until the end of the Cold War. A fission bomb is exploded next to fusion fuel in the solid form of lithium deuteride. Additional fusion and fission fuels are enclosed in a dense shell of U U. At the same time that the uranium shell reflects the neutrons back into the fuel to enhance its fusion, the fast-moving neutrons cause the plentiful and inexpensive U U to fission, part of what allows thermonuclear bombs to be so large.
Of course, not all applications of nuclear physics are as destructive as the weapons described above. Hundreds of nuclear fission power plants around the world attest to the fact that controlled fission is both practical and economical. Given growing concerns over global warming, nuclear power is often seen as a viable alternative to energy derived from fossil fuels. For decades, fusion reactors have been deemed the energy of the future. A safer, cleaner, and more abundant potential source of energy than its fission counterpart, images of the fusion reactor have been conjured up each time the need for a renewable, environmentally friendly resource is discussed.
Now, after more than half a century of speculating, some scientists believe that fusion reactors are nearly here. In creating energy by combining atomic nuclei, the fusion reaction holds many advantages over fission. First, fusion reactions are more efficient, releasing 3 to 4 times more energy than fission per gram of fuel.
Furthermore, unlike fission reactions that require heavy elements like uranium that are difficult to obtain, fusion requires light elements that are abundant in nature. The greatest advantage of the fusion reaction, however, is in its ability to be controlled.
While traditional nuclear reactors create worries about meltdowns and radioactive waste, neither is a substantial concern with the fusion reaction.
Consider that fusion reactions require a large amount of energy to overcome the repulsive Coulomb force and that the byproducts of a fusion reaction are largely limited to helium nuclei.
In order for fusion to occur, hydrogen isotopes of deuterium and tritium must be acquired. Once acquired, the hydrogen isotopes are injected into an empty vessel and subjected to temperature and pressure great enough to mimic the conditions at the core of our Sun.
Using carefully controlled high-frequency radio waves, the hydrogen isotopes are broken into plasma and further controlled through an electromagnetic field. As the electromagnetic field continues to exert pressure on the hydrogen plasma, enough energy is supplied to cause the hydrogen plasma to fuse into helium. Once the plasma fuses, high-velocity neutrons are ejected from the newly formed helium atoms. Those high velocity neutrons, carrying the excess energy stored within bonds of the original hydrogen, are able to travel unaffected by the applied magnetic field.
In doing so, they strike a barrier around the nuclear reactor, transforming their excess energy to heat. The heat is then harvested to make steam that drives turbines. The historical concern with nuclear fusion reactors is that the energy required to control the electromagnetic field is greater than the energy harvested from the hydrogen atoms.
However, recent research by both Lockheed Martin engineers and scientists at the Lawrence Livermore National Laboratory has yielded exciting theoretical improvements in efficiency. As an Amazon Associate we earn from qualifying purchases. Want to cite, share, or modify this book? This book is Creative Commons Attribution License 4. Changes were made to the original material, including updates to art, structure, and other content updates.
Skip to Content Go to accessibility page. Physics My highlights. Table of contents. Chapter Review. Test Prep. By the end of this section, you will be able to do the following: Explain nuclear fission Explain nuclear fusion Describe how the processes of fission and fusion work in nuclear weapons and in generating nuclear power.
Teacher Support The learning objectives in this section will help your students master the following standards: 8 Science concepts. The student knows simple examples of atomic, nuclear, and quantum phenomena. The student is expected to: C describe the significance of mass-energy equivalence and apply it in explanations of phenomena such as nuclear stability, fission, and fusion. Teacher Support [BL] [OL] To ensure understanding, ask students why it is not likely that a stable atom would naturally decay.
First, energy is put into a large nucleus when it absorbs a neutron. Acting like a struck liquid drop, the nucleus deforms and begins to narrow in the middle. Since fewer nucleons are in contact, the repulsive Coulomb force is able to break the nucleus into two parts with some neutrons also flying away.
This depends on several factors, including how many neutrons are produced in an average fission and how easy it is to make a particular type of nuclide fission. Control rods adjust neutron flux so that it is self-sustaining. In case the reactor overheats and boils the water away, the chain reaction terminates, because water is needed to slow down the neutrons. This inherent safety feature can be overwhelmed in extreme circumstances. Calculating Energy from a Kilogram of Fissionable Fuel Calculate the amount of energy produced by the fission of 1.
Nuclear Fission Click to view content. Teacher Support The reading in this subsection is dense. Teacher Support For students struggling with the analogy, there is a popular carnival game with a bowling ball, called Roller Bowler, that models the potential energy well affectively. If the nuclei have enough kinetic energy to get over the Coulomb repulsion hump, they combine, release energy, and drop into a deep attractive well.
Teacher Support For the following proton-proton cycle, have students check to make sure that mass number and charge are conserved for each of the four equations. For each equation, ask how energy is emitted. It is important to move slowly through this section. Students will likely be unfamiliar with the terms positron and electron neutrino.
For now, express the positron as positive electron not a proton and the electron neutrino as a massless electron. Energy released diffuses slowly to the surface, with the exception of neutrinos, which escape immediately. Energy production remains stable because of negative-feedback effects. The energy yield depends on the amount of uranium and the time it can be held together before it disassembles itself. The superior fissionability of plutonium has made it the preferred bomb material.
Department of Energy. Teacher Support [BL] [OL] [AL] Note that the hydrogen bomb is a fusion bomb, as its energy can only be released by combining multiple hydrogen nuclei together.
The outer shell of U U serves to reflect some neutrons back into the fuel, causing more fusion, and it boosts the energy output by fissioning itself when neutron energies become high enough. Fusion Reactors For decades, fusion reactors have been deemed the energy of the future. The magnetic field lines are used to confine the high-temperature plasma purple. Research is currently being done to increase the efficiency of the tokamak confinement model.
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