32.6 Fission
3 min read•june 18, 2024
splits heavy atomic nuclei, releasing energy and neutrons. This process powers nuclear reactors and weapons. reactions can be controlled for electricity generation or unleashed in atomic bombs, demonstrating the immense potential and risks of nuclear technology.
Understanding fission is crucial for grasping nuclear energy's role in modern society. It highlights the delicate balance between harnessing atomic power for beneficial uses and managing its destructive potential, shaping global energy and security landscapes.
Nuclear Fission
Process of nuclear fission
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- involves the splitting of a heavy atomic nucleus (uranium or plutonium) into lighter nuclei
- Occurs when a neutron collides with a nucleus, causing it to become unstable and split
- Key components of nuclear fission:
- Fissile material capable of undergoing fission ( or )
- Neutron initiates the fission reaction by colliding with the fissile nucleus
- are lighter nuclei produced from the splitting of the heavy nucleus
- are additional neutrons released during the fission process, which can trigger further fission reactions
- Significant amount of energy released in the form of kinetic energy of and gamma radiation
- by the fissile nucleus is crucial for initiating the fission process
Products of fission reactions
- Fission reactions produce various products and release energy:
- Fission fragments are two or more lighter nuclei formed from the split of the heavy nucleus ( and from the fission of )
- Typically 2-3 prompt neutrons are released per fission event, which can initiate further fission reactions if absorbed by nearby fissile nuclei
- Approximately 200 MeV (million electron volts) of energy is released per fission event
- Majority of energy is in the kinetic energy of fission fragments (about 168 MeV)
- Prompt gamma radiation and neutron kinetic energy account for the remaining energy
- Fission reactions demonstrate Einstein's famous equation,
- Total mass of fission products is less than the initial mass of the fissile nucleus
- The "missing" mass is converted into the released energy according to
- The difference in between the initial nucleus and the fission products accounts for the energy release
Controlled vs uncontrolled chain reactions
- Fission occurs when prompt neutrons from one fission event trigger further fission events
- Can be controlled or uncontrolled, depending on the application
- Controlled fission chain reaction:
- Used in nuclear power plants to generate electricity
- Fission rate is carefully regulated using control rods and moderators
- Control rods absorb excess neutrons to prevent runaway chain reactions
- Moderators slow down neutrons to increase their likelihood of causing fission
- Allows for a steady, sustainable release of energy
- Uncontrolled fission chain reaction:
- Occurs in nuclear weapons (atomic bombs)
- Fission rate rapidly increases, leading to a massive release of energy in a short time
- No control mechanisms are used to regulate the reaction
- Can cause significant destruction and radioactive fallout
Nuclear reactors and safety considerations
- Nuclear reactors harness the energy from controlled fission reactions to generate electricity
- Key components of a include:
- Fuel rods containing fissile material
- Control rods to regulate the reaction rate
- to slow down neutrons
- Coolant to remove heat and generate steam for power generation
- Safety considerations in nuclear reactors:
- Proper containment to prevent release of radioactive materials
- Monitoring of reactor core temperature and pressure
- Emergency shutdown systems
- Management of radioactive waste products
- of fission products is an important factor in waste management and environmental impact
Key Terms to Review (30)
Binding energy: Binding energy is the energy required to disassemble a nucleus into its component protons and neutrons. It is a measure of the stability of a nucleus and is equivalent to the mass defect of the nucleus.
Binding Energy: Binding energy is the amount of energy required to separate a nucleus into its individual protons and neutrons. It represents the strong nuclear force that holds the nucleus together, and it is a crucial concept in understanding nuclear stability, radioactive decay, and nuclear reactions such as fusion and fission.
Breeder Reactor: A breeder reactor is a type of nuclear reactor that generates more fissile material than it consumes, producing more fuel than it uses. This is achieved through the breeding of fissile material, such as plutonium-239, from non-fissile isotopes like uranium-238.
Breeder reactors: Breeder reactors are a type of nuclear reactor that generate more fissile material than they consume. They convert fertile isotopes like uranium-238 into fissile isotopes such as plutonium-239 through the process of neutron absorption and subsequent nuclear reactions.
Breeding: Breeding in nuclear physics refers to the process of generating more fissile material from fertile material within a nuclear reactor. This is crucial for sustaining long-term nuclear reactions and producing fuel for reactors.
Chain Reaction: A chain reaction is a self-sustaining sequence of reactions where the products of one reaction trigger additional reactions, causing the entire process to repeat itself in a continuous cycle. This concept is particularly important in the context of nuclear fission and nuclear weapons.
Critical mass: Critical mass is the minimum amount of fissile material needed to maintain a self-sustaining nuclear chain reaction. It is essential for the operation of nuclear reactors and atomic bombs.
Critical Mass: Critical mass is the minimum amount of fissile material required to sustain a nuclear chain reaction. It is a crucial concept in the context of nuclear fission and the development of nuclear weapons.
Criticality: Criticality refers to the state of a nuclear chain reaction when it becomes self-sustaining. It is a crucial concept in controlling nuclear reactors and ensuring safety in medical applications of nuclear physics.
Enrico Fermi: Enrico Fermi was an Italian physicist who made significant contributions to the development of nuclear physics and the understanding of nuclear fission. He is widely regarded as one of the most important figures in the history of modern physics.
Fissile: Fissile materials are those that are capable of undergoing nuclear fission, a process where the nucleus of an atom splits into smaller nuclei, releasing a large amount of energy in the process. This property is crucial in the context of nuclear physics and the development of nuclear technology.
Fission: Fission is the process of splitting heavy atomic nuclei, such as uranium or plutonium, into lighter nuclei. This process releases a large amount of energy and is the basis for nuclear power generation and nuclear weapons.
Fission fragments: Fission fragments are the atomic nuclei produced by the splitting of a heavier nucleus during nuclear fission. These fragments are typically highly unstable and radioactive, emitting particles as they decay.
Fission Fragments: Fission fragments are the smaller nuclei that result from the splitting of a heavier atomic nucleus, such as uranium or plutonium, during the process of nuclear fission. These fragments are produced when the nucleus of a heavy atom is bombarded with a neutron, causing it to split into two or more lighter nuclei.
Half-life: Half-life is the time required for half of the radioactive nuclei in a sample to undergo decay. This concept is crucial for understanding the behavior of unstable isotopes as they transform into more stable forms, providing insights into nuclear radioactivity, the detection of radiation, and the principles governing nuclear decay and conservation laws.
Isotope: Isotopes are atoms of the same element that have the same number of protons in their nucleus but a different number of neutrons. This results in isotopes having the same atomic number but different mass numbers, leading to slight variations in their physical and chemical properties.
Light-Water Reactor: A light-water reactor (LWR) is a type of nuclear reactor that uses ordinary water (as opposed to heavy water) as the coolant and neutron moderator. It is the most widely used type of nuclear reactor for the generation of electric power.
Lise Meitner: Lise Meitner was an Austrian-Swedish physicist who made significant contributions to the understanding of nuclear physics, particularly in the discovery of nuclear fission. She is considered one of the most important female scientists of the 20th century and played a crucial role in the development of our knowledge about the process of nuclear fission.
Manhattan Project: The Manhattan Project was a top-secret research and development program undertaken during World War II by the United States, the United Kingdom, and Canada to develop the first nuclear weapons. It was a groundbreaking scientific endeavor that led to the creation of the atomic bomb, which would have a profound impact on the topics of fission and nuclear weapons.
Moderator: A moderator is a material used in nuclear reactors to slow down high-energy neutrons produced during the fission process, allowing for a controlled and sustained nuclear chain reaction. The moderator helps maintain the critical state of the reactor by reducing the speed of neutrons, making them more likely to be absorbed by fissile nuclei and continue the fission process.
Neutron Absorption: Neutron absorption is the process by which a nucleus captures a neutron, leading to the formation of a new nucleus with a different atomic number and mass. This phenomenon is crucial in the context of nuclear fission, where the absorption of neutrons by fissile nuclei initiates the fission process and releases energy.
Neutron-induced fission: Neutron-induced fission is a nuclear reaction where a heavy nucleus, such as Uranium-235, absorbs a neutron and splits into two smaller nuclei, releasing energy and more neutrons. This process is fundamental in both nuclear reactors and atomic bombs.
Nuclear Chain Reaction: A nuclear chain reaction is a self-sustaining sequence of nuclear fissions in which the release of neutrons from one fission reaction triggers additional fissions, releasing more neutrons and causing the process to repeat itself. This phenomenon is central to the operation of nuclear reactors and the detonation of nuclear weapons.
Nuclear fission: Nuclear fission is the process in which a nucleus of a heavy atom splits into two or more smaller nuclei, along with the release of energy. This reaction is often initiated by the absorption of a neutron.
Nuclear Fission: Nuclear fission is the process of splitting heavy atomic nuclei, such as uranium or plutonium, into lighter nuclei. This process releases a large amount of energy that can be harnessed for various applications, including nuclear power generation and the development of nuclear weapons.
Nuclear Reactor: A nuclear reactor is a device that houses and controls a nuclear fission chain reaction, which is used to generate heat and ultimately produce electricity. It is the core component of a nuclear power plant, where the energy released from the splitting of atomic nuclei is harnessed for practical purposes.
Plutonium-239: Plutonium-239 is a radioactive isotope of the element plutonium. It is a key component in the production of nuclear weapons and is also used in some nuclear power reactors. Plutonium-239 is central to the topics of fission and nuclear weapons, as it is the primary fissile material used in the cores of nuclear weapons and in some nuclear reactor fuel.
Prompt Neutrons: Prompt neutrons are neutrons that are released immediately during the fission process, as opposed to delayed neutrons that are released later. These prompt neutrons are crucial in sustaining the fission chain reaction and controlling the nuclear reactor's power output.
Supercriticality: Supercriticality occurs when a nuclear chain reaction becomes self-sustaining and the neutron population increases exponentially. It is a state where each fission event causes more than one subsequent fission event.
Uranium-235: Uranium-235 is a fissile isotope of the element uranium that is the primary fuel used in nuclear reactors and nuclear weapons. It is the only naturally occurring isotope that is fissile, meaning it can sustain a nuclear chain reaction. This unique property of uranium-235 makes it central to the topics of half-life, binding energy, nuclear fission, and nuclear weapons.