This document provides definitions and explanations of key nuclear physics terms including:
- Nucleon, nuclide, and isotope refer to particles and types of atoms based on their nuclear composition.
- Mass-energy equivalence means that mass and energy are interchangeable and mass can be converted to energy via nuclear reactions.
- Mass defect and binding energy explain how binding nuclei together releases energy and lowers the total mass.
- Nuclear fission is the splitting of heavy nuclei by neutron absorption or bombardment, releasing energy, neutrons, and lighter elements. Criticality refers to a sustained fission chain reaction.
This document provides an overview of basic nuclear physics concepts. It discusses the structure of atoms including protons, neutrons, and electrons. It defines terms like atomic number, mass number, and isotopes. It explains concepts such as binding energy, radioactive decay modes (alpha, beta, gamma), activity, and half-life. Radioactive decay is described as the process by which unstable atoms emit particles or radiation to become more stable. Common decay types and their products are outlined.
This document discusses nuclear reactions and different types of nuclear processes including nuclear fission and nuclear fusion. It explains that nuclear reactions occur when atomic nuclei interact, changing the composition but conserving mass and charge. Nuclear fission is the splitting of heavy atomic nuclei after absorbing neutrons, releasing energy, while nuclear fusion is the combining of light nuclei into heavier ones. Controlled nuclear fusion research aims to replicate the energy process of the sun for energy production on Earth.
The document summarizes key topics in the chapter on nuclear physics, including:
1) The structure and properties of the nucleus, including its composition of protons and neutrons.
2) The discovery of the neutron by James Chadwick in 1932, which helped explain nuclear structure.
3) The strong and weak nuclear forces that bind nucleons together in the nucleus.
This presentation discusses nuclear binding energy. It defines binding energy as the energy required to break a whole system into separate parts. Specifically, nuclear binding energy is the energy needed to disassemble or break the nucleus of an atom into its component neutrons and protons. The presentation provides an example calculation of the binding energy of oxygen-16. It also includes a graph of the binding energy curve, which shows binding energy per nucleon peaks at an atomic mass number of around 60, indicating particularly stable atomic nuclei.
The document discusses three types of radioactive decay: alpha, beta, and gamma decay. Alpha decay occurs when a nucleus ejects an alpha particle, consisting of two protons and two neutrons. Beta decay can occur in two ways - beta minus decay where a neutron is converted to a proton and an electron is emitted, and beta plus decay where a proton is converted to a neutron and a positron is emitted. Gamma decay occurs when a nucleus in an excited state drops to a lower energy state by emitting a high energy photon.
The document provides an overview of the nuclear shell model. It discusses the historical development of the model from 1927 to 1935. It then presents three pieces of evidence from experiments that supported developing the shell model to describe nuclear properties, including excitation energies, neutron absorption cross-sections, and neutron separation energies. The rest of the document outlines how the shell model was developed theoretically by introducing a Woods-Saxon potential well and spin-orbit coupling to explain nuclear magic numbers and properties like ground and excited state configurations and nuclear magnetic moments. The model provides good predictions but has some limitations for deformed nuclei.
This document provides an introduction to nuclear physics. It discusses the history and development of the field, from the discovery of radioactivity and the electron in the early 20th century to the proposal of the liquid drop model and development of the semi-empirical mass formula to describe nuclear structure. Key events discussed include Rutherford's discovery of the nuclear model of the atom, the discovery of the neutron by Chadwick, and Yukawa's proposal of the meson to explain nuclear forces. The introduction concludes by outlining the chapters to follow on topics like nuclear decay, fusion, fission, and reactor physics.
The document discusses various types of nuclear reactions. It defines nuclear reactions as processes where two nuclei or nuclear particles collide and produce different products than the initial particles. It describes several types of nuclear reactions including elastic and inelastic scattering, pickup and stripping reactions, compound nuclear reactions, radioactive capture, and photo disintegration. Elastic scattering involves the projectile and outgoing particles being the same, while inelastic scattering results in a loss of energy and particles scattered in different directions with different energies. Pickup reactions involve a gain of nucleons from the target, and stripping reactions involve one or more nucleons captured from the projectile. The document provides examples of each type of reaction.
This document provides an overview of basic nuclear physics concepts. It discusses the structure of atoms including protons, neutrons, and electrons. It defines terms like atomic number, mass number, and isotopes. It explains concepts such as binding energy, radioactive decay modes (alpha, beta, gamma), activity, and half-life. Radioactive decay is described as the process by which unstable atoms emit particles or radiation to become more stable. Common decay types and their products are outlined.
This document discusses nuclear reactions and different types of nuclear processes including nuclear fission and nuclear fusion. It explains that nuclear reactions occur when atomic nuclei interact, changing the composition but conserving mass and charge. Nuclear fission is the splitting of heavy atomic nuclei after absorbing neutrons, releasing energy, while nuclear fusion is the combining of light nuclei into heavier ones. Controlled nuclear fusion research aims to replicate the energy process of the sun for energy production on Earth.
The document summarizes key topics in the chapter on nuclear physics, including:
1) The structure and properties of the nucleus, including its composition of protons and neutrons.
2) The discovery of the neutron by James Chadwick in 1932, which helped explain nuclear structure.
3) The strong and weak nuclear forces that bind nucleons together in the nucleus.
This presentation discusses nuclear binding energy. It defines binding energy as the energy required to break a whole system into separate parts. Specifically, nuclear binding energy is the energy needed to disassemble or break the nucleus of an atom into its component neutrons and protons. The presentation provides an example calculation of the binding energy of oxygen-16. It also includes a graph of the binding energy curve, which shows binding energy per nucleon peaks at an atomic mass number of around 60, indicating particularly stable atomic nuclei.
The document discusses three types of radioactive decay: alpha, beta, and gamma decay. Alpha decay occurs when a nucleus ejects an alpha particle, consisting of two protons and two neutrons. Beta decay can occur in two ways - beta minus decay where a neutron is converted to a proton and an electron is emitted, and beta plus decay where a proton is converted to a neutron and a positron is emitted. Gamma decay occurs when a nucleus in an excited state drops to a lower energy state by emitting a high energy photon.
The document provides an overview of the nuclear shell model. It discusses the historical development of the model from 1927 to 1935. It then presents three pieces of evidence from experiments that supported developing the shell model to describe nuclear properties, including excitation energies, neutron absorption cross-sections, and neutron separation energies. The rest of the document outlines how the shell model was developed theoretically by introducing a Woods-Saxon potential well and spin-orbit coupling to explain nuclear magic numbers and properties like ground and excited state configurations and nuclear magnetic moments. The model provides good predictions but has some limitations for deformed nuclei.
This document provides an introduction to nuclear physics. It discusses the history and development of the field, from the discovery of radioactivity and the electron in the early 20th century to the proposal of the liquid drop model and development of the semi-empirical mass formula to describe nuclear structure. Key events discussed include Rutherford's discovery of the nuclear model of the atom, the discovery of the neutron by Chadwick, and Yukawa's proposal of the meson to explain nuclear forces. The introduction concludes by outlining the chapters to follow on topics like nuclear decay, fusion, fission, and reactor physics.
The document discusses various types of nuclear reactions. It defines nuclear reactions as processes where two nuclei or nuclear particles collide and produce different products than the initial particles. It describes several types of nuclear reactions including elastic and inelastic scattering, pickup and stripping reactions, compound nuclear reactions, radioactive capture, and photo disintegration. Elastic scattering involves the projectile and outgoing particles being the same, while inelastic scattering results in a loss of energy and particles scattered in different directions with different energies. Pickup reactions involve a gain of nucleons from the target, and stripping reactions involve one or more nucleons captured from the projectile. The document provides examples of each type of reaction.
1) Einstein's mass-energy equivalence relation E=mc^2 relates mass and energy. One atomic mass unit (amu) is defined as 1/12 the mass of one carbon-12 atom, which is 1.6605x10-27 kg.
2) The binding energy of a nucleus is the energy required to break it into protons and neutrons. It is related to the mass defect based on differences in nuclear and nucleon masses. Binding energy per nucleon is highest for mid-sized nuclei like iron-56.
3) The binding energy curve shows binding energy per nucleon peaks around mass numbers 4, 8, 12, 16 and 20, which have even numbers of protons and neutrons.
The document discusses the history and development of theories of blackbody radiation and the concept of the photon. It describes how (1) classical physics could not fully explain experimental observations of blackbody radiation, (2) Planck resolved this issue by proposing that the radiation emitted by cavity walls was quantized into discrete energy packets called quanta (later known as photons), and (3) his theory accurately described blackbody radiation distribution and resolved prior inconsistencies like the ultraviolet catastrophe.
The nuclear shell model was developed in 1949 and describes how protons and neutrons occupy discrete energy levels, or shells, within the nucleus, analogous to the way electrons occupy shells in atoms. It explains several nuclear properties that the liquid drop model could not, such as magic numbers and spin. Nuclei with magic numbers of protons or neutrons are particularly stable due to their filled shells. Evidence for the shell structure includes increased stability and separation energies at magic numbers, and the stable isotopes at the end of radioactive decay chains all having magic numbers of protons. The model makes assumptions like an average central force field and independent nucleon motion within orbits. However, it has limitations like not explaining schmidt lines or higher energy nuclear states fully
- Nuclear fission involves splitting large nuclei like uranium, releasing energy. Fusion joins light nuclei like hydrogen, also releasing energy.
- Fission is used in nuclear power plants and bombs. Fusion powers stars and could be an energy source on Earth if containment and high temperature issues are solved.
- The binding energy curve shows that mid-sized nuclei are most stable, and that fission and fusion involving less stable nuclei release energy.
Nuclear physics studies the building blocks and interactions of atomic nuclei. The field is the basis for applications like nuclear power, nuclear bombs, nuclear medicine, and radiocarbon dating. Atoms consist of a nucleus containing protons and neutrons, surrounded by orbiting electrons. Radioactivity occurs when unstable atomic nuclei decay by emitting particles like alpha and beta particles or gamma rays. Nuclear fission and fusion can release energy as nuclei split or combine.
Rutherford's model of an atom and alpha particle scattering experimentHarsh Rajput
Rutherford conducted an experiment where he aimed a beam of alpha particles at a thin gold foil. Most particles passed through but some bounced straight back, indicating the atom had a small, dense, positively charged nucleus. This led to Rutherford's model of the atom as a small nucleus surrounded by orbiting electrons. However, this model is unstable as electromagnetic theory suggests electrons in circular orbits would radiate energy and eventually collide with the nucleus. A new model was needed to explain the stability of atoms.
This document summarizes a seminar presentation on nuclear fission and fusion. It begins with acknowledging those who assisted in preparing the topic. It then outlines the topics to be covered, including the history of fission and fusion discovery, definitions, types of fission (spontaneous and induced), chain reactions, applications, and differences between fission and fusion. Details are provided on spontaneous and induced fission. The document concludes by defining nuclear fission as the splitting of a large atom into smaller ones through neutron impact and nuclear fusion as several small nuclei fusing together to release energy.
This document provides an introduction to particle physics, including:
- A brief history of discoveries of the elementary constituents of matter like protons, neutrons, electrons.
- An overview of the four fundamental forces and how they control particle behavior.
- Explanations of conservation laws, neutrino theory, and early experiments verifying mass-energy equivalence.
- Descriptions of the Standard Model of particle families, forces, the quark model, and antimatter discoveries.
1. Nuclear physics studies the composition and interactions of atomic nuclei. Nuclei are composed of protons and neutrons, which interact via the strong nuclear force.
2. Nuclear reactions such as fission, fusion, and radioactive decay involve changes in nuclear binding energies and mass defects. Fission releases energy as heavy nuclei split into lighter nuclei, while fusion releases energy by combining light nuclei into heavier ones.
3. Key concepts include the strong nuclear force, mass defect and binding energy, radioactive decay and half-lives, and the types of radiation involved in different nuclear reactions like fission and fusion.
The document discusses several topics in atomic and nuclear physics:
1) Light exhibits properties of both waves and particles, known as wave-particle duality. Photons and the photoelectric effect show light acting as a particle, while experiments like interference and diffraction show its wavelike properties.
2) The Compton effect demonstrates that X-rays can lose energy when scattered by electrons, indicating X-rays act as particles. X-rays are also produced when high-energy electrons interact with atoms.
3) Atoms have distinct energy levels, and photons are emitted or absorbed when electrons transition between these levels. The energy of photons equals the energy difference of the levels.
The document discusses properties of the nucleus, including:
- The nucleus contains positively charged protons and uncharged neutrons.
- Isotopes of an element have the same number of protons but different numbers of neutrons.
- A mass spectrometer can be used to separate isotopes based on their different masses, producing a characteristic pattern on a photographic plate.
Physics Final Presentation: Nuclear PhysicsChris Wilson
This document discusses the four fundamental forces in nuclear physics - gravitation, electromagnetism, strong nuclear force, and weak nuclear force. It describes nuclear fusion and half-life decay. It also explains the types of particles involved in different types of nuclear decay such as alpha, beta, and gamma particles and emissions.
1) Classical theories could not explain the spectrum of blackbody radiation, predicting infinite energy at short wavelengths.
2) Planck hypothesized that the oscillators could only emit or absorb energy in discrete quantized units proportional to frequency, avoiding the infinity.
3) This led to Planck's law of radiation, which correctly described the blackbody spectrum using a quantum of action hν. This founding of quantum theory resolved the ultraviolet catastrophe.
The document discusses nuclear reactions and radioactivity. It describes three types of radiation emitted by radioactive substances: alpha, beta, and gamma rays. It also discusses radioactive decay, balancing nuclear equations, three types of radioactive decay, and half-life. Different nuclear reactions like fission and fusion are sources of energy. Radioisotopes have medical uses, and radiation can have biological effects.
The document discusses several key concepts relating to blackbody radiation:
1) A blackbody is an idealized object that absorbs all electromagnetic radiation falling on it without reflecting or transmitting any.
2) The purpose of the experiment was to measure the intensity of electromagnetic waves emitted by a blackbody as its temperature increases, and to use Wien's and Stephan Boltzmann's laws.
3) The experiment had many flaws and issues, resulting in unreliable data that did not match theoretical predictions.
Almost all matter in the universe is concentrated within atomic nuclei composed of neutrons and protons. Radioactive decay occurs when an unstable atomic nucleus loses energy by emitting radiation such as alpha particles, beta particles, or gamma rays. The number of protons defines the element, while the total number of protons and neutrons is the mass number. Radioactive emissions are random, but the average rate of decay follows statistical laws defined by half-life.
This document provides an introduction to basic nuclear physics concepts. It defines key terms like atomic nucleus, nucleons, nuclides, isotopes, isobars, isotones, and isomers. It explains how to calculate the number of neutrons in a nucleus and provides examples of nuclear classification. The document also outlines general nuclear properties such as size, mass, density, and charge. It concludes with some applications of nuclear physics such as electric power generation, national security, medical diagnosis and treatment, radioactive dating, and household uses.
The document discusses the four fundamental forces: gravitational, electromagnetic, nuclear, and weak. It summarizes that the nuclear force was discovered after neutrons were discovered in 1932, and holds nucleons together in the nucleus. The nuclear force is charge independent, very strong but short range, repulsive at short distances, and acts through the exchange of pions between nucleons. The document provides details on the Yukawa potential and uncertainty principle as they relate to the nuclear force. It poses a multiple choice question about identifying an incorrect statement regarding the nuclear force.
Rutherford performed experiments scattering alpha particles off a thin gold foil that could not be explained by Thomson's atomic model. Rutherford's results showed that a small percentage of particles were scattered at very large angles, which could only be explained if atoms had small, dense nuclei. This led to Rutherford's model of the atom, with electrons in circular orbits around a tiny, positively charged nucleus containing almost all the mass of the atom. The Rutherford model successfully explained the stability of atoms through the balance of electric and centrifugal forces on orbiting electrons.
Nuclear physics involves understanding atoms through experiments like Rutherford's gold foil experiment which showed that atoms have a small, dense nucleus surrounded by empty space. Radiation like alpha, beta, and gamma rays is used in applications such as cancer treatment, electricity generation, and radiocarbon dating which relies on the radioactive decay of carbon-14 to determine the age of ancient materials.
Physics 2008 PNEB (PUNTLAND NATIONAL EXAMINATION BOARD)Eng.Abdulahi hajji
This document provides instructions for a Form 4 Physics exam in Somalia. It consists of 14 pages including multiple choice and structured questions worth a total of 100 marks. Candidates are instructed to answer all questions in the spaces provided and show all working. No extra paper or calculators are allowed. The exam will last 2 hours and 10 minutes total, including 10 minutes before the start for reading.
1) Einstein's mass-energy equivalence relation E=mc^2 relates mass and energy. One atomic mass unit (amu) is defined as 1/12 the mass of one carbon-12 atom, which is 1.6605x10-27 kg.
2) The binding energy of a nucleus is the energy required to break it into protons and neutrons. It is related to the mass defect based on differences in nuclear and nucleon masses. Binding energy per nucleon is highest for mid-sized nuclei like iron-56.
3) The binding energy curve shows binding energy per nucleon peaks around mass numbers 4, 8, 12, 16 and 20, which have even numbers of protons and neutrons.
The document discusses the history and development of theories of blackbody radiation and the concept of the photon. It describes how (1) classical physics could not fully explain experimental observations of blackbody radiation, (2) Planck resolved this issue by proposing that the radiation emitted by cavity walls was quantized into discrete energy packets called quanta (later known as photons), and (3) his theory accurately described blackbody radiation distribution and resolved prior inconsistencies like the ultraviolet catastrophe.
The nuclear shell model was developed in 1949 and describes how protons and neutrons occupy discrete energy levels, or shells, within the nucleus, analogous to the way electrons occupy shells in atoms. It explains several nuclear properties that the liquid drop model could not, such as magic numbers and spin. Nuclei with magic numbers of protons or neutrons are particularly stable due to their filled shells. Evidence for the shell structure includes increased stability and separation energies at magic numbers, and the stable isotopes at the end of radioactive decay chains all having magic numbers of protons. The model makes assumptions like an average central force field and independent nucleon motion within orbits. However, it has limitations like not explaining schmidt lines or higher energy nuclear states fully
- Nuclear fission involves splitting large nuclei like uranium, releasing energy. Fusion joins light nuclei like hydrogen, also releasing energy.
- Fission is used in nuclear power plants and bombs. Fusion powers stars and could be an energy source on Earth if containment and high temperature issues are solved.
- The binding energy curve shows that mid-sized nuclei are most stable, and that fission and fusion involving less stable nuclei release energy.
Nuclear physics studies the building blocks and interactions of atomic nuclei. The field is the basis for applications like nuclear power, nuclear bombs, nuclear medicine, and radiocarbon dating. Atoms consist of a nucleus containing protons and neutrons, surrounded by orbiting electrons. Radioactivity occurs when unstable atomic nuclei decay by emitting particles like alpha and beta particles or gamma rays. Nuclear fission and fusion can release energy as nuclei split or combine.
Rutherford's model of an atom and alpha particle scattering experimentHarsh Rajput
Rutherford conducted an experiment where he aimed a beam of alpha particles at a thin gold foil. Most particles passed through but some bounced straight back, indicating the atom had a small, dense, positively charged nucleus. This led to Rutherford's model of the atom as a small nucleus surrounded by orbiting electrons. However, this model is unstable as electromagnetic theory suggests electrons in circular orbits would radiate energy and eventually collide with the nucleus. A new model was needed to explain the stability of atoms.
This document summarizes a seminar presentation on nuclear fission and fusion. It begins with acknowledging those who assisted in preparing the topic. It then outlines the topics to be covered, including the history of fission and fusion discovery, definitions, types of fission (spontaneous and induced), chain reactions, applications, and differences between fission and fusion. Details are provided on spontaneous and induced fission. The document concludes by defining nuclear fission as the splitting of a large atom into smaller ones through neutron impact and nuclear fusion as several small nuclei fusing together to release energy.
This document provides an introduction to particle physics, including:
- A brief history of discoveries of the elementary constituents of matter like protons, neutrons, electrons.
- An overview of the four fundamental forces and how they control particle behavior.
- Explanations of conservation laws, neutrino theory, and early experiments verifying mass-energy equivalence.
- Descriptions of the Standard Model of particle families, forces, the quark model, and antimatter discoveries.
1. Nuclear physics studies the composition and interactions of atomic nuclei. Nuclei are composed of protons and neutrons, which interact via the strong nuclear force.
2. Nuclear reactions such as fission, fusion, and radioactive decay involve changes in nuclear binding energies and mass defects. Fission releases energy as heavy nuclei split into lighter nuclei, while fusion releases energy by combining light nuclei into heavier ones.
3. Key concepts include the strong nuclear force, mass defect and binding energy, radioactive decay and half-lives, and the types of radiation involved in different nuclear reactions like fission and fusion.
The document discusses several topics in atomic and nuclear physics:
1) Light exhibits properties of both waves and particles, known as wave-particle duality. Photons and the photoelectric effect show light acting as a particle, while experiments like interference and diffraction show its wavelike properties.
2) The Compton effect demonstrates that X-rays can lose energy when scattered by electrons, indicating X-rays act as particles. X-rays are also produced when high-energy electrons interact with atoms.
3) Atoms have distinct energy levels, and photons are emitted or absorbed when electrons transition between these levels. The energy of photons equals the energy difference of the levels.
The document discusses properties of the nucleus, including:
- The nucleus contains positively charged protons and uncharged neutrons.
- Isotopes of an element have the same number of protons but different numbers of neutrons.
- A mass spectrometer can be used to separate isotopes based on their different masses, producing a characteristic pattern on a photographic plate.
Physics Final Presentation: Nuclear PhysicsChris Wilson
This document discusses the four fundamental forces in nuclear physics - gravitation, electromagnetism, strong nuclear force, and weak nuclear force. It describes nuclear fusion and half-life decay. It also explains the types of particles involved in different types of nuclear decay such as alpha, beta, and gamma particles and emissions.
1) Classical theories could not explain the spectrum of blackbody radiation, predicting infinite energy at short wavelengths.
2) Planck hypothesized that the oscillators could only emit or absorb energy in discrete quantized units proportional to frequency, avoiding the infinity.
3) This led to Planck's law of radiation, which correctly described the blackbody spectrum using a quantum of action hν. This founding of quantum theory resolved the ultraviolet catastrophe.
The document discusses nuclear reactions and radioactivity. It describes three types of radiation emitted by radioactive substances: alpha, beta, and gamma rays. It also discusses radioactive decay, balancing nuclear equations, three types of radioactive decay, and half-life. Different nuclear reactions like fission and fusion are sources of energy. Radioisotopes have medical uses, and radiation can have biological effects.
The document discusses several key concepts relating to blackbody radiation:
1) A blackbody is an idealized object that absorbs all electromagnetic radiation falling on it without reflecting or transmitting any.
2) The purpose of the experiment was to measure the intensity of electromagnetic waves emitted by a blackbody as its temperature increases, and to use Wien's and Stephan Boltzmann's laws.
3) The experiment had many flaws and issues, resulting in unreliable data that did not match theoretical predictions.
Almost all matter in the universe is concentrated within atomic nuclei composed of neutrons and protons. Radioactive decay occurs when an unstable atomic nucleus loses energy by emitting radiation such as alpha particles, beta particles, or gamma rays. The number of protons defines the element, while the total number of protons and neutrons is the mass number. Radioactive emissions are random, but the average rate of decay follows statistical laws defined by half-life.
This document provides an introduction to basic nuclear physics concepts. It defines key terms like atomic nucleus, nucleons, nuclides, isotopes, isobars, isotones, and isomers. It explains how to calculate the number of neutrons in a nucleus and provides examples of nuclear classification. The document also outlines general nuclear properties such as size, mass, density, and charge. It concludes with some applications of nuclear physics such as electric power generation, national security, medical diagnosis and treatment, radioactive dating, and household uses.
The document discusses the four fundamental forces: gravitational, electromagnetic, nuclear, and weak. It summarizes that the nuclear force was discovered after neutrons were discovered in 1932, and holds nucleons together in the nucleus. The nuclear force is charge independent, very strong but short range, repulsive at short distances, and acts through the exchange of pions between nucleons. The document provides details on the Yukawa potential and uncertainty principle as they relate to the nuclear force. It poses a multiple choice question about identifying an incorrect statement regarding the nuclear force.
Rutherford performed experiments scattering alpha particles off a thin gold foil that could not be explained by Thomson's atomic model. Rutherford's results showed that a small percentage of particles were scattered at very large angles, which could only be explained if atoms had small, dense nuclei. This led to Rutherford's model of the atom, with electrons in circular orbits around a tiny, positively charged nucleus containing almost all the mass of the atom. The Rutherford model successfully explained the stability of atoms through the balance of electric and centrifugal forces on orbiting electrons.
Nuclear physics involves understanding atoms through experiments like Rutherford's gold foil experiment which showed that atoms have a small, dense nucleus surrounded by empty space. Radiation like alpha, beta, and gamma rays is used in applications such as cancer treatment, electricity generation, and radiocarbon dating which relies on the radioactive decay of carbon-14 to determine the age of ancient materials.
Physics 2008 PNEB (PUNTLAND NATIONAL EXAMINATION BOARD)Eng.Abdulahi hajji
This document provides instructions for a Form 4 Physics exam in Somalia. It consists of 14 pages including multiple choice and structured questions worth a total of 100 marks. Candidates are instructed to answer all questions in the spaces provided and show all working. No extra paper or calculators are allowed. The exam will last 2 hours and 10 minutes total, including 10 minutes before the start for reading.
1. The document discusses the characteristics of precision, accuracy, and sensitivity which are important when selecting a measuring instrument.
2. Precision refers to the consistency or reproducibility of measurements, while accuracy refers to how close measurements are to the true or accepted value.
3. Sensitivity is the ability of an instrument to detect small changes in the measured quantity. More sensitive instruments have finer scale divisions and can measure smaller amounts.
Ernest Rutherford conducted an experiment where he fired alpha particles at a thin gold foil. He expected the particles to pass through the foil with only slight deflection based on the plum pudding atomic model. However, he discovered that some particles were deflected at large angles or reflected straight back, indicating the presence of a small, dense nucleus. This led Rutherford to propose the nuclear model of the atom with positive charge and mass concentrated at the center.
The document discusses geometric shapes related to circles such as spheres, hemispheres, and sectors. It provides formulas for calculating the surface area and volume of spheres and hemispheres. Formulas are given for finding the circumference, area, and radii of circles. The document also discusses converting between degrees and radians and provides formulas for calculating arc length, area of sectors, and area of segments of circles.
An addiction is a complex brain disease that causes physical and mental dependence on drugs. Prolonged drug use changes the brain's structure and communication, making it difficult to stop using drugs. While addiction can be treated through rehabilitation, relapses and health issues often remain. Many factors contribute to drug addiction, including environment, biology, development, and peer pressure. Different drugs have various short-term and long-term effects on physical and mental health. Seeking help from a drug helpline is recommended for those struggling with addiction.
Assignment Physical Chemistry By Anam FatimaNathan Mathis
1. The document discusses nuclear chemistry concepts including nuclear stability factors, mass defect vs binding energy, nuclear reactions such as fission and fusion, and atomic bombs.
2. It provides examples of calculating binding energy and discusses the difference between mass defect and binding energy. Mass defect represents the mass of energy binding nuclei while binding energy is the energy required to split a nucleus.
3. Nuclear fission is described as the splitting of atomic nuclei when bombarded by neutrons or other particles, releasing energy. Uranium-235 and plutonium-239 undergo fission, splitting into smaller nuclei along with neutron release. Neutrons are ideal for inducing fission since they have no charge.
1. Nuclear chemistry deals with changes in the nucleus of atoms, which are the source of radioactivity and nuclear power. It studies nuclear particles, forces, and reactions.
2. Nuclear reactions differ from chemical reactions in that the nucleus of an element takes part rather than just electrons, and a much larger amount of energy is evolved. Reaction rates of nuclear reactions are dependent on nuclear concentration but not influenced by temperature or catalysts.
3. Radioactive decay occurs via three types of radiation: alpha, beta, and gamma. Alpha decay decreases mass and atomic number by units of 4 and 2, respectively. Beta decay does not change mass number but increases atomic number by 1. Gamma decay does not change mass or atomic number
This document provides an introduction to nuclear chemistry. It discusses the basic components of atoms and how nuclear reactions differ from chemical reactions. It describes the three types of nuclear radiation (alpha, beta, gamma) and their properties. The document also covers radioactive decay and concepts such as decay constant, half-life, and average life. Additional topics include nuclear stability factors, mass defect and binding energy, and the application of radioisotopes as tracers and in radiotherapy, mutation breeding, and carbon dating.
This document provides an introduction to nuclear physics and radioactivity. It discusses:
1) The discovery of radioactivity and the nucleus. Rutherford's scattering experiment in 1911 revealed the existence of the nucleus as the source of radioactivity.
2) The structure of the nucleus, including its composition of protons and neutrons (nucleons), atomic number, mass number, isotopes, and typical size.
3) Nuclear stability and binding energy. The strong nuclear force holds nuclei together, and nuclei with intermediate mass numbers have the highest binding energy per nucleon. Only certain combinations of protons and neutrons produce stable nuclei.
1) Nuclear fusion and fission reactions can release large amounts of energy. Fusion occurs when light nuclei join together, as in the Sun, while fission occurs when heavy nuclei split apart.
2) A graph of binding energy per nucleon shows that mid-sized nuclei are most stable, and that both fission and fusion reactions produce fragments with higher binding energy, releasing energy.
3) Nuclear fission in uranium can be triggered by neutrons and produce a chain reaction releasing many neutrons, as used in nuclear weapons and controlled in nuclear power plants. Nuclear fusion is even more powerful but requires extremely high temperatures and pressures to overcome repulsion between positively charged nuclei.
The document discusses the types of radiation emitted during radioactive decay. It describes alpha, beta, and neutron radiation as particulate radiation emitted from atomic nuclei. Alpha radiation consists of helium nuclei, beta radiation can be electrons or positrons, and neutron radiation emits neutrons. Electron capture and internal conversion are also discussed as alternative decay processes.
1. Radioactive decay occurs through three main types: alpha, beta, and gamma decay. Alpha decay involves emitting an alpha particle, beta decay changes the nucleus via electron or positron emission, and gamma decay releases energy without changing the nucleus.
2. Nuclear reactions can be classified as fission or fusion. Fission occurs when heavy nuclei split into lighter ones and releases energy. Fusion combines light nuclei into heavier ones and also releases energy. These reactions are accompanied by changes in mass and binding energy.
3. Atoms are made of protons, neutrons, and electrons. The Standard Model describes all fundamental particles and their interactions via exchange particles like photons. Quarks combine to form hadrons like protons and
Nuclear chemistry deals with changes that occur in the nucleus of an atom. It involves the study of radioactivity, nuclear reactions and transformations, and nuclear properties. Some key topics covered include nuclear fusion, fission, radioactive decay, and chain reactions. The liquid drop model describes atomic nuclei as behaving like liquid drops, with nucleons held together by nuclear forces analogous to surface tension. Nuclear stability is influenced by factors such as these nuclear forces, mass defect, and binding energy. Mass defect represents the difference between a nucleus's calculated and observed mass, with the difference corresponding to the energy binding the nucleus. Binding energy refers to the energy released when nucleons come together or required to separate them.
1. The mass defect for the helium nucleus is 0.03039 atomic mass units or 5.046×10−29 kg. This mass defect is equivalent to 4.54×10−12 J of energy needed to separate the nucleus according to Einstein's mass-energy equivalence formula.
2. The binding energy per nucleon is typically around 8 MeV and indicates the stability of the nucleus. More stable nuclei have higher binding energies per nucleon. During radioactive decay, the daughter nucleus is more stable and has a higher binding energy per nucleon than the parent nucleus. The energy released during decay comes from the mass defect between the parent and daughter nuclei.
3. Calculating the mass defect and applying Einstein
Nuclear binding energy is the energy required to split an atom's nucleus into smaller nuclei or nucleons. It is equal to the mass defect (the difference between the total mass of nucleons and the actual mass of the nucleus) times the speed of light squared. Binding energy varies with mass number, being highest for mid-sized nuclei and lower for light and heavy nuclei. Elements with higher binding energy per nucleon are more stable as their nuclei are more tightly bound.
B sc i chemistry i u i nuclear chemistry aRai University
Nuclear chemistry deals with changes that occur in the nucleus of atoms. These changes are the source of radioactivity and nuclear power. The nucleus contains protons and neutrons, called nucleons. Some atoms are unstable and their nuclei spontaneously break down, releasing particles and energy. Elements whose nuclei emit radiation are radioactive. The spontaneous breakdown of unstable atoms is called radioactive decay or disintegration. There are three main types of radioactive decay: alpha emission, beta emission, and gamma emission. Radioactive decay occurs at a constant rate described by the decay constant. Isotopes are atoms of the same element with different numbers of neutrons, while isobars have the same mass number but different atomic numbers. The half-life of a radioactive
B sc_I_General chemistry U-I Nuclear chemistry Rai University
1) Nuclear chemistry deals with changes that occur in the nucleus of elements, which are the source of radioactivity and nuclear power.
2) Some atoms are unstable and their nuclei spontaneously break down, releasing particles and energy. The elements whose nuclei emit radiation are radioactive.
3) There are three main types of radioactive emissions: alpha, beta, and gamma. Alpha involves emitting an alpha particle, beta involves emitting an electron, and gamma involves emitting gamma rays.
This document provides information on nuclear chemistry and radioactive decay. It defines key terms like nucleus, nucleons, protons, neutrons, and discusses nuclear stability and different types of radioactive decay. Examples are given to calculate nuclear binding energy from mass defect and the amount of energy released from fission and fusion reactions. The kinetics of radioactive decay are described and follow first order rate laws. Sample problems demonstrate calculating half-lives, decay constants, and the time it takes for only a certain percentage of a radioactive sample to remain.
This document provides an overview of key concepts in nuclear physics covered in Chapter 43, including:
1) Properties of nuclei such as nucleon number, radius, density, isotopes, and nuclear magnetic moments.
2) Nuclear models including the liquid drop model and shell model to describe nuclear stability.
3) Nuclear binding energy and how it depends on proton and neutron numbers. The nucleus with the highest binding energy per nucleon is 62Ni.
4) Radioactivity and different types of nuclear decay processes, including alpha decay, beta decay, and gamma decay. Stable nuclides lie along an asymmetric line in the nuclear chart that favors more neutrons than protons for higher atomic masses.
This document provides instructions for navigating a presentation on nuclear physics. It begins with directions for viewing the presentation as a slideshow and advancing through it. It then lists the chapter topics covered in the presentation, including the nucleus, nuclear decay, nuclear reactions, and particle physics. The objectives and content of each section are briefly outlined.
Introduction to Class 12 Physics - Nuclei:
In the realm of physics, the study of atomic nuclei constitutes a pivotal and intriguing segment, forming the nucleus of Class 12 Physics. Delving into the heart of matter, this section unravels the intricacies of the atomic nucleus, where protons and neutrons converge to define the essence of elements. From the formidable forces that bind these particles to the dynamic processes of radioactive decay, Class 12 Physics - Nuclei unveils the mysteries that govern the core of our physical reality.
As students embark on this journey, they will explore the minuscule dimensions of the nucleus, grapple with the potent forces that operate within, and unravel the applications that extend from nuclear power generation to medical diagnostics. The study of nuclei encapsulates the very essence of matter and energy, offering profound insights into the fundamental nature of the universe.
Through an exploration of nuclear reactions, radioactivity, and the applications that span from energy production to medical advancements, Class 12 Physics - Nuclei equips students with a comprehensive understanding of the microscopic world that shapes the macroscopic reality we inhabit. The journey into the heart of the atom awaits, promising a voyage into the fundamental building blocks that define the physical universe.
For more updates, visit- www.vavaclasses.com
This document provides an overview of key concepts in nuclear physics covered in Chapter 43 of University Physics. It discusses properties of nuclei such as nucleon number, radius, and density. It also covers nuclear binding energy, radioactive decay, and models of nuclear structure including the liquid drop model and shell model. Examples are provided to illustrate concepts like alpha decay, beta decay, gamma emission, and the calculation of half-lives. The document concludes with a discussion of natural radioactivity and decay chains.
The document discusses key topics in nuclear physics including:
1) The structure and properties of the nucleus including its composition of protons and neutrons.
2) The discovery of the neutron by James Chadwick in 1932 which helped explain nuclear reactions.
3) The strong and weak nuclear forces that bind nucleons together in the nucleus.
4) Key nuclear properties such as atomic number, mass number, and isotopes which have the same number of protons but different neutrons.
5) Other concepts like mass defect, binding energy, and mass-energy equation which are important for understanding nuclear processes.
This document discusses nuclear binding energy and nuclear models. It begins by explaining how the mass of an atom is calculated based on its nuclear mass and electron mass. It then discusses how the actual nuclear mass is less than the sum of its nucleon masses due to binding energy. Greater binding energy leads to more stable nuclei. The binding energy per nucleon varies with atomic mass number A and peaks around iron. Light nuclei can undergo fusion to form heavier nuclei, releasing energy. Heavy nuclei can undergo fission to form lighter nuclei, also releasing energy. Separation energies reflect the stability of removing particles from nuclei. Nuclear spins and dipole moments are also discussed.
1. Lord Rutherford discovered the nucleus through alpha particle scattering experiments, finding that atoms consist of a small, dense, positively charged nucleus surrounded by orbiting electrons.
2. The nucleus contains positively charged protons and neutral neutrons, collectively called nucleons. The number of protons is the atomic number and the total number of protons and neutrons is the mass number.
3. Isotopes are atoms with the same atomic number but different mass numbers, such as the three isotopes of hydrogen: deuterium, ordinary hydrogen, and tritium.
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UiPath Test Automation using UiPath Test Suite series, part 5
(Ebook) physics nuclear physics
1. 1.04 - NUCLEAR PHYSICS RCT STUDY GUIDE
-1- Issued 05/95
LEARNING OBJECTIVES:
1.04.01 Identify the definitions of the following terms:
a. Nucleon
b. Nuclide
c. Isotope
1.04.02 Identify the basic principles of the mass-energy equivalence concept.
1.04.03 Identify the definitions of the following terms:
a. Mass defect
b. Binding energy
c. Binding energy per nucleon|
1.04.04 Identify the definitions of the following terms:
a. Fission
b. Criticality
c. Fusion
INTRODUCTION
Nuclear power is made possible by the process of nuclear fission. Fission is but one of a
large number of nuclear reactions which can take place. Many reactions other than fission
are quite important because they affect the way we deal with all aspects of handling and
storing nuclear materials. These reactions include radioactive decay, scattering, and
radiative capture. This lesson is designed to provide a understanding of the forces present
within an atom.
2. 1.04 - NUCLEAR PHYSICS RCT STUDY GUIDE
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1.04.01 Identify the definitions of the following terms:
a. Nucleon
b. Nuclide
c. Isotope
NUCLEAR TERMINOLOGY
There are several terms used in the field of nuclear physics that an RCT must understand.
Nucleon
Neutrons and protons are found in the nucleus of an atom, and for this reason are
collectively referred to as nucleons. A nucleon is defined as a constituent particle of the
atomic nucleus, either a neutron or a proton.
Nuclide
A species of atom characterized by the constitution of its nucleus, which is specified by its
atomic mass and atomic number (Z), or by its number of protons (Z), number of neutrons
(N), and energy content. A listing of all nuclides can be found on the "Chart of the
Nuclides," which will be introduced in a later lesson.
Isotope
This term was mentioned in Lesson 1.03 when we discussed the concepts of atomic mass
and atomic weight. Isotopes are defined as nuclides which have the same number of
protons but different numbers of neutrons. Therefore, any nuclides which have the
same atomic number (i.e. the same element) but different atomic mass numbers are
isotopes.
For example, hydrogen has three isotopes, known as Protium, Deuterium and Tritium.
Since hydrogen has one proton, any hydrogen atom will have an atomic number of 1.
However, the atomic mass numbers of the three isotopes are different: Protium (H-1) has
an mass number of 1 (1 proton, no neutrons), deuterium (D or H-2) has a mass number of
2 (1 proton, 1 neutron), and tritium (T or H-3) has a mass number of 3 (1 proton,
2 neutrons).
3. 1.04 - NUCLEAR PHYSICS RCT STUDY GUIDE
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1.04.02 Identify the basic principles of the mass-energy equivalence concept.
MASS-ENERGY EQUIVALENCE
Of fundamental concern in nuclear reactions is the question of whether a given reaction is
possible and, if so, how much energy is required to initiate the reaction or is released when
the reaction occurs. The key to these questions lies in the relationship between the mass
and energy of an object.
The theory that relates the two was proposed by Albert Einstein in 1905. Einstein's special
theory of relativity culminated in the famous equation:
E = mc2
where: E = Energy
m = mass|
c = speed of light
This equation expresses the equivalence of mass and energy, meaning that mass may be
transformed to energy and vice versa. Because of this equivalence the two are often
referred to collectively as mass-energy.
The mass-energy equivalence theory implies that mass and energy are interchangeable.
The theory further states that the mass of an object depends on its speed. Thus, all
matter contains energy by virtue of its mass. It is this energy source that is tapped to|
obtain nuclear energy.
The Law of Conservation of Energy applies to mass as well as energy, since the two are
equivalent. Therefore, in any nuclear reaction the total mass-energy is conserved i.e.|
mass-energy cannot be created or destroyed. This is of importance when it becomes|
necessary to calculate the energies of the various types of radiation which accompany the
radioactive decay of nuclei.
Pair Annihilation: An Example of Mass to Energy Conversion
An interaction which occurs is pair annihilation, where two particles with mass,
specifically a positron and an electron (negatron), collide and are transformed into two
rays (photons) of electromagnetic energy. A positron is essentially an anti-electron,
4. 2(0.00054858026 amu)
1
×
931.478 MeV
amu
1.022 MeV
1.04 - NUCLEAR PHYSICS RCT STUDY GUIDE
-4- Issued 05/95
1.04.03 Identify the definitions of the following terms:
a. Mass defect
b. Binding energy
c. Binding energy per nucleon
having a positive charge. When a positron collides with an electron, both particles are
annihilated and their mass is converted completely to electromagnetic energy. (This
interaction will be discussed in Lesson 1.07 "Interactions of Radiation with Matter.")
If the mass of an electron/positron is 0.00054858026 amu, the resulting annihilation
energy (radiation) resulting from the collision would be:
MASS DEFECT AND BINDING ENERGY
With an understanding of the equivalence of mass and energy, we can now examine the
principles which lie at the foundation of nuclear power.
Mass Defect
As we said earlier, the mass of an atom is comes almost entirely from the nucleus. If a
nucleus could be disassembled to its constituent parts, i.e., protons and neutrons, it would
be found that the total mass of the atom is less than the sum of the masses of the
individual protons and neutrons. This is illustrated in Figure 1 below.
5. 1.04 - NUCLEAR PHYSICS RCT STUDY GUIDE
-5- Issued 05/95
Figure 1. Atomic Scale
This slight difference in mass is known as the mass defect, (pronounced "delta"), and
can be computed for each nuclide, using the following equation.
= (Z)(M ) + (Z)(M ) + (A-Z)(M ) - Mp e n a
where: = mass defect
Z = atomic number
M = mass of a proton (1.00728 amu)p
M = mass of a electron (0.000548 amu)e
A = mass number
M = mass of a neutron (1.00867 amu)n
M = atomic mass (from Chart of the Nuclides)| a
For example, consider an isotope of Lithium, Li:7
3
A = 7
Z = 3
M= 7.01600 amu (per Chart of the Nuclides)
Therefore:
= (3)(1.00728) + (3)(0.00055) + (7-3)(1.00867) - (7.01600)
= (3.02184) + (0.00165) + (4.03468) - (7.01600)
= (7.05817) - (7.01600)
= 0.04217 amu
Binding Energy
The mass defect of Li is 0.04217 amu. This is the mass that is apparently "missing", but,7
3
in fact, has been converted to energy)the energy that binds the lithium atom nucleus
6. BE
0.04217 amu
1
931.478 MeV
amu
39.28 MeV
39.28 MeV
7 nucleons
5.61 MeV per nucleon
1.04 - NUCLEAR PHYSICS RCT STUDY GUIDE
-6- Issued 05/95
together, or its binding energy. Binding energy is the energy equivalent of mass defect.
Note from the Lesson 1.02 Conversion Tables that:
1 amu = 931.478 MeV
So, if we multiply the mass defect by this number we can calculate the binding energy.
From this we have determined the energy converted from mass in the formation of the
nucleus. We will see that it is also the energy that must be applied to the nucleus in order
to break it apart.
Another important calculation is that of the binding energy of a neutron. This calculation
is of significance when the energetics of the fission process are considered. For example,
when U-235 absorbs a neutron, the compound nucleus U-236 is formed (see NUCLEAR
FISSION later in this lesson). The change in mass ( m) is calculated and then converted
to its energy equivalent:
m = (m + m ) - mn U235 U236
m = (1.00867 + 235.0439) - 236.0456
m = 0.0070 amu
0.0070 amu × 931.5 MeV/amu = 6.52 MeV
Thus, the nucleus possesses an excitation energy of 6.52 MeV when U-235 absorbs a
neutron.
Binding Energy per Nucleon
If the total binding energy of a nucleus is divided by the total number of nucleons in the
nucleus, the binding energy per nucleon is obtained. This represents the average energy
which must be supplied in order to remove a nucleon from the nucleus. For example,
using the Li atom as before, the binding energy per nucleon would be calculated as7
3
follows:
7. 0
20
40
60
80
100
120
140
160
180
200
220
240
Mass Number (A)
10
9
8
7
6
5
4
3
2
1
0
H-1
He-3
Li-6
B-10
He-4
Al-27
Cu-63
Sn-120
Pt-195
U-238
Th-232
1.04 - NUCLEAR PHYSICS RCT STUDY GUIDE
-7- Issued 05/95
Figure 2. Binding Energy vs. Mass Number
If the binding energy per nucleon is plotted as a function of mass number (total number of
nucleons) for each element, a curve is obtained (see Figure 2). The binding energy per
nucleon peaks at about 8.5 MeV for mass numbers 40 - 120 and decreases to about 7.6
MeV per nucleon for uranium.
The binding energy per nucleon decreases with increasing mass number above mass 56
because as more protons are added, the proton-proton repulsion increases faster than the
nuclear attraction. Since the repulsive forces are increasing, less energy must be supplied,
on the average, to remove a nucleon. That is why there are no stable nuclides with mass
numbers beyond that of 208.
NUCLEAR TRANSFORMATION EQUATIONS
Using the X format, equations can be written which depict a transformation that hasA
Z
occurred in a nucleus or nuclei. Since it is an equation, both sides must be equal.
Therefore, the total mass-energy on the left must be equal to the total mass-energy on the
8. 1.04 - NUCLEAR PHYSICS RCT STUDY GUIDE
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1.04.05 Identify the definitions of the following terms:
a. Fission
b. Criticality
c. Fusion
right. Keeping in mind that mass and energy are equivalent, any difference in total mass is
accounted for as energy released in the transformation. This energy release is called the Q
value. For example, the alpha decay of Radium-226 would be depicted as:
Ra Rn + + Q226 222 4
88 86 2
The energy release, represented by Q in this case, is manifest as the kinetic energy of the
high-speed alpha particle, as well as the recoil of the Radon-222 atom.
NUCLEAR FISSION
As we have shown, the nucleus of a single atom could be the source of considerable
energy. If the nucleus could be split so as to release this energy it could be used to
generate power. Therefore, if the energy from millions of atoms were released it would be
a great source of power. This thinking is the basis for nuclear power.
When a free neutron strikes a nucleus, one of the processes which may occur is the
absorption of the neutron by the nucleus. It has been shown that the absorption of a
neutron by a nucleus raises the energy of the system by an amount equal to the binding
energy of the neutron. Under some circumstances, this absorption may result in the
splitting of the nucleus into at least two smaller nuclei with an accompanying release
of energy. This process is called fission. Two or three neutrons are usually released
during this type of transformation.
In order to account for how this process is possible, use is made of the liquid drop model
of the nucleus. This model is based on the observation that the nucleus, in many ways,
resembles a drop of liquid. The liquid drop is held together by cohesive forces between
molecules, and when the drop is deformed the cohesive forces may be insufficient to
restore the drop to its original shape. Splitting may occur, although in this case, there
would be no release of energy. Figure 3 illustrates this model.
9. c. d.
e.
a. b.
1.04 - NUCLEAR PHYSICS RCT STUDY GUIDE
-9- Issued 05/95
Figure 3. Liquid Drop Model of Fission
10. 1.04 - NUCLEAR PHYSICS RCT STUDY GUIDE
-10- Issued 05/95
The absorption of a neutron raises the energy of the system by an amount equal to the
binding energy of the neutron. This energy input causes deformation of the nucleus, but if
it is not of sufficient magnitude, the nucleon-nucleon attractive forces will act to return the
nucleus to its original shape. If the energy input is sufficiently large, the nucleus may
reach a point of separation, and a fission has occurred. The energy required to drive the
nucleus to the point of separation is called the critical energy for fission, E . The valuesc
of E for various nuclei can be calculated, based on a knowledge of the forces which act toc
hold the nucleus together.
An example of a fission is shown below, involving neutron absorption by U-235:
U + n U* Ba + Kr + 3( n) + Q235 1 236 138 95 1
92 0 92 56 36 0
On the average, approximately 200 MeV of energy is released per fission.
The fission process can be "energetically" explained by comparing the critical energy for
fission with the amount of energy input, i.e., the neutron binding energy. For U-238 and
Th-232, the critical energy for fission is greater than the neutron binding energy.
Therefore, an additional amount of energy must be supplied in order for fission to occur in
these nuclei. This additional energy is in the form of neutron kinetic energy, and confirms
the observation that fission occurs in these fissionable nuclei only when the neutron has
approximately 1 MeV of kinetic energy.
The situation is quite different for U-235, U-233, and Pu-239. In these cases, the neutron
binding energy exceeds the critical energy for fission. Thus, these nuclei may be fissioned
by thermal, or very low energy, (0.025 eV) neutrons.
As mentioned earlier, the new elements which are formed as a result of the fissioning of an
atom are unstable because their N/P ratios are too high. To attain stability, the fission
fragments will undergo various transformations depending on the degree of instability.
Along with the neutrons immediately released during fission, a highly unstable element
may give off several neutrons to try to regain stability. This, of course, makes more
neutrons available to cause more fissions and is the basis for the chain reaction used to
produce nuclear power. The excited fission product nuclei will also give off other forms
of radiation in an attempt to achieve a stable status. These include beta and gamma
radiation.
11. Prompt
Neutrons
Prompt
Neutrons
235
U
Thermal
Neutron
Neutrons
Delayed
ß
ß
ß
v
v
1.04 - NUCLEAR PHYSICS RCT STUDY GUIDE
-11- Issued 05/95
Figure 4. Fission process in U initiated by a thermal neutron.235
Criticality
Criticality is the condition in which the neutrons produced by fission are equal to the
number of neutrons in the previous generation. This means that the neutrons in one
generation go on to produce an equal number of fission events, which events in turn
produce neutrons that produce another generation of fissions, and so forth. This
continuation results in the self-sustained chain reaction mentioned above. Figure 5 gives a
simple illustration of the chain reaction that occurs in a criticality.
As one can discern, this reaction requires control. If the population of neutrons remains
constant, the chain reaction will be sustained. The system is thus said to be critical.
However, if too many neutrons escape from the system or are absorbed but do not
produce a fission, then the system is said to be subcritical and the chain reaction will
eventually stop.
On the other hand, if the two or three neutrons produced in one fission each go on to
produce another fission, the number of fissions and the production of neutrons will
increase exponentially. In this case the chain reaction is said to be supercritical.
12. INITIAL
FISSION
N
Frag
Frag
U-235
N
N
SECOND
FISSION
Frag
Frag
U-235
N
Escape N Escape
CAPTURE
Impurity
THIRD
FISSION
Frag Frag
U-235
N
N
N
Escape
U-235
U-235
FOURTH
FISSION
Frag
U-235
Frag
FIFTH
FISSION
N
N
CAPTURE
Impurity
N
SURFACE
1.04 - NUCLEAR PHYSICS RCT STUDY GUIDE
-12- Issued 05/95
Figure 5. Self-sustaining Chain reaction
K = Effective Multiplication Constanteff
K <1 = Subcritical Conditioneff
K = 1 = Critical Conditioneff
K >1 = Supercritical Conditioneff
Table 1 - The Effective Multiplication Constant
In nuclear reactors this concept is expressed as the effective multiplication constant or|
K . K is defined as the ratio of the number of neutrons in the reactor in one generation| eff eff
to the number of neutrons in the previous generation. On the average, 2.5 neutrons are|
emitted per uranium fission. If K has a value of greater than 1, the neutron flux is| eff
increasing, and conversely, if it has a value of less than 1, the flux is decreasing with time.|
Table 1 illustrates the reactor condition for various values of the multiplication constant.|
|
In a subcritical reactor, the neutron flux and power output will die off in time. When|
critical, the reactor operates at a steady neutron and power output. A reactor must be|
supercritical to increase the neutron flux and power level.|
13. 1.04 - NUCLEAR PHYSICS RCT STUDY GUIDE
-13- Issued 05/95
Therefore, the population of neutrons must be controlled in order to control the number of
fissions that occur. Otherwise, the results could be devastating.
Fusion
Another reaction between nuclei which can be the source of power is fusion. Fusion is
the act of combining or "fusing" two or more atomic nuclei. Fusion thus builds atoms.
The process of fusing nuclei into a larger nucleus with an accompanying release of energy
is called fusion.
Fusion occurs naturally in the sun and is the source of its energy. The reaction is initiated
under the extremely high temperatures and pressure in the sun whereby H interacts with1
1
C. Hydrogen is then converted to helium and energy is liberated in the form of heat.12
6
4( H) He + 2(e ) + 24.7 MeV1 4 2+ +
1 2
What occurs in the above equation is the combination of 4 hydrogen atoms, giving a total
of 4 protons and 4 electrons. 2 protons combine with 2 electrons to form 2 neutrons,
which combined with the remaining 2 protons forms a helium nucleus, leaving 2 electrons
and a release of energy.
REFERENCES:
1. "Nuclear Chemistry"; Harvey, B. G.
2. "Physics of the Atom"; Wehr, M. R. and Richards, J. A. Jr.
3. "Introduction to Atomic and Nuclear Physics"; Oldenburg, O. and Holladay, W. G.
4. "Health Physics Fundamentals"; General Physics Corp.
5. "Basic Radiation Protection Technology"; Gollnick, Daniel; Pacific Radiation
Press; 1983
6. "Fundamental Manual Vol. 1"; Defense Reactor Training Program, Entry Level
Training Program
7. "Introduction to Health Physics"; Cember, Herman; 2nd ed.; Pergamon Press;
1983
8. ANL-88-26 (1988) "Operational Health Physics Training"; Moe, Harold; Argonne
National Laboratory, Chicago
9. NAVPERS 10786 (1958) "Basic Nuclear Physics"; Bureau of Naval Personnel