ATOMIC AND NUCLEAR PHYSICS
A knowledge of atomic and nuclear physics is essential to nuclear engineers, who deal with nuclear reactors. It should be noted that atomic and nuclear physics is very extensive branch of science. Nuclear reactor physics
belongs to an applied physics. Reactor physics, particle physics or
other branches of modern physics have common fundamentals. Atomic and
nuclear physics describes fundamental particles (i.e. electrons,
protons, neutrons), their structure, properties and behavior.
Atomic and nuclear physics are not the same. The term atomic physics is often associated with nuclear power, due to the synonymous use of atomic and nuclear in standard English. However, physicists distinguish between atomic and nuclear physics. The atomic physics deals with the atom as a system consisting of a nucleus and electrons. The nuclear physics deals with the nucleus as a system consisting of a nucleons (protons and neutrons). Main difference is in the scale. While the term atomic deals with 1Å = 10-10m, where Å is an ångström (according to Anders Jonas Ångström), the term nuclear deals with 1femtometre = 1fermi = 10-15m.
Nuclear physics is the field of physics that studies the constituents (protons and neutrons) and interactions of atomic nuclei. The most commonly known applications of nuclear physics are nuclear power generation, but the modern nuclear physics contains also particle physics, which is taught in close association with nuclear physics. The nuclear physics has provided application in many fields, including those in nuclear medicine (Positron Emission Tomography, isotopes production, etc.) and magnetic resonance imaging, ion implantation in materials engineering, and radiocarbon dating in geology and archaeology.
Thus the symbol 1H refers to the nuclide of hydrogen with a single proton as nucleus. 2H is the hydrogen nuclide with a neutron as well as a proton in the nucleus (2H is also called deuterium or heavy hydrogen). Atoms such as 1H, 2H whose nuclei contain the same number of protons but different number of neutrons (different A) are known as isotopes. Uranium, for instance, has three isotopes occuring in nature – 238U, 235U and 234U. The stable isotopes (plus a few of the unstable isotopes) are the atoms that are found in the naturally occuring elements in nature. However, they are not found in equal amounts. Some isotopes of a given element are more abundant than others. For example 99,27% of naturally occuring uranium atoms are the isotope 238U, 0,72% are the isotope 235U and 0,0055% are the isotope 234U. Exact structure of atoms is described by Atomic Theory and Theory of Nuclear Structure.
Atomic and nuclear physics are not the same. The term atomic physics is often associated with nuclear power, due to the synonymous use of atomic and nuclear in standard English. However, physicists distinguish between atomic and nuclear physics. The atomic physics deals with the atom as a system consisting of a nucleus and electrons. The nuclear physics deals with the nucleus as a system consisting of a nucleons (protons and neutrons). Main difference is in the scale. While the term atomic deals with 1Å = 10-10m, where Å is an ångström (according to Anders Jonas Ångström), the term nuclear deals with 1femtometre = 1fermi = 10-15m.
Atomic Physics
Atomic physics is the field of physics that studies atoms as an isolated system of electrons and an atomic nucleus. It is primarily concerned with the arrangement of electrons around the nucleus and the processes by which these arrangements change. This includes ions as well as neutral atoms and, unless otherwise stated, for the purposes of this discussion it should be assumed that the term atom includes ions. Atomic physics also help to understand the physics of molecules, but there is also molecular physics, which describes physical properties of molecules.Nuclear Physics
Nuclear physics is the field of physics that studies the constituents (protons and neutrons) and interactions of atomic nuclei. The most commonly known applications of nuclear physics are nuclear power generation, but the modern nuclear physics contains also particle physics, which is taught in close association with nuclear physics. The nuclear physics has provided application in many fields, including those in nuclear medicine (Positron Emission Tomography, isotopes production, etc.) and magnetic resonance imaging, ion implantation in materials engineering, and radiocarbon dating in geology and archaeology.
FUNDAMENTAL PARTICALS:
nly a few of these fundamental particles (in fact, some of these are
not fundamental particles) are very important in nuclear engineering.
Nuclear engineering or theory of nuclear reactors operates with much
better known subatomic particles such as:
- Electrons. The electrons are negatively charged, almost massless particles that nevertheless account for most of the size of the atom. Electrons were discovered by Sir John Joseph Thomson in 1897. Electrons are located in an electron cloud, which is the area surrounding the nucleus of the atom. The electron is only one member of a class of elementary particles, which forms an atom.
- Protons. The protons are positively charged, massive particles that are located inside the atomic nucleus. Protons were discovered by Ernest Rutherford in the year 1919, when he performed his gold foil experiment.
- Neutron. Neutrons are located in the nucleus with the protons. Along with protons, they make up almost all of the mass of the atom. Neutrons were discovered by James Chadwick in 1932, when he demonstrated that penetrating radiation incorporated beams of neutral particles.
- Photon. A photon is an elementary particle, the force carrier for the electromagnetic force. The photon is the quantum of light (discrete bundle of electromagnetic energy). Photons are always in motion and, in a vacuum, have a constant speed of light to all observers (c = 2.998 x 108 m/s).
- Neutrino. A neutrino is an elementary particle, one of particles which make up the universe. Neutrinos are electrically neutral, weakly interacting and therefore able to pass through great distances in matter without being affected by it.
- Positron. Positron is an antiparticle of a negative electron. Positrons, also called positive electron, have a positive electric charge and have the same mass and magnitude of charge as the electron. An annihilation occurs, when a low-energy positron collides with a low-energy electron.
ATOMIC AND NUCLEAR STRUCTURE:
he atom consist of a small but massive nucleus surrounded by a cloud of rapidly moving electrons. The nucleus is composed of protons and neutrons. Total number of protons in the nucleus is called the atomic number of the atom and is given the symbol Z. The total electrical charge of the nucleus is therefore +Ze, where e (elementary charge) equals to 1,602 x 10-19 coulombs.
In a neutral atom there are as many electrons as protons moving about
nucleus. It is the electrons that are responsible for the chemical
bavavior of atoms, and which identify the various chemical elements.
Hydrogen (H), for example , consist of one electron and one proton. The number of neutrons in a nucleus is known as the neutron number and is given the symbol N. The total number of nucleons, that is, protons and neutrons in a nucleus, is equal to Z + N = A, where A is called the atomic mass number. The various species of atoms whose nuclei contain particular numbers of protons and neutrons are called nuclides. Each nuclide is denoted by chemical symbol of the element (this specifies Z) with tha atomic mass number as supescript.Thus the symbol 1H refers to the nuclide of hydrogen with a single proton as nucleus. 2H is the hydrogen nuclide with a neutron as well as a proton in the nucleus (2H is also called deuterium or heavy hydrogen). Atoms such as 1H, 2H whose nuclei contain the same number of protons but different number of neutrons (different A) are known as isotopes. Uranium, for instance, has three isotopes occuring in nature – 238U, 235U and 234U. The stable isotopes (plus a few of the unstable isotopes) are the atoms that are found in the naturally occuring elements in nature. However, they are not found in equal amounts. Some isotopes of a given element are more abundant than others. For example 99,27% of naturally occuring uranium atoms are the isotope 238U, 0,72% are the isotope 235U and 0,0055% are the isotope 234U. Exact structure of atoms is described by Atomic Theory and Theory of Nuclear Structure.
- Atomic Theory. Atomic theory is a scientific theory of the nature of matter, which states that matter is composed of discrete units called atoms. The word atom comes from the Ancient Greek adjective atomos, meaning “uncuttable”. Today it is known that also atoms are divisible. Atomic Theory consist of many models and discoveries, which gradually formed this theory.
- Theory of Nuclear Structure. Understanding the structure of the atomic nucleus is one of the central challenges in modern nuclear physics.
MASS AND ENERGY:
Nuclear energy comes either from spontaneous nuclei conversions or
induced nuclei conversions. Among these conversions (nuclear reactions)
belong for example nuclear fission, nuclear decay and nuclear fusion.
Conversions are associated with mass and energy changes. One of the
striking results of Einstein’s theory of relativity is that mass and
energy are equivalent and convertible, one into the other. Equivalence
of the mass and energy is described by Einstein’s famous formula:
, where M is the small amount of mass and C is the speed of light.
What that means? If the nuclear energy is generated (splitting atoms, nuclear fussion), a small amount of mass transforms into the pure energy (such as kinetic energy, thermal energy, or radiant energy).
Example:
The energy equivalent of one gram (1/1000 of a kilogram) of mass is equivalent to:
89.9 terajoules
25.0 million kilowatt-hours (≈ 25 GW·h)
21.5 billion kilocalories (≈ 21 Tcal)
85.2 billion BTUs
or to the energy released by combustion of the following:
21.5 kilotons of TNT-equivalent energy (≈ 21 kt)
568,000 US gallons of automotive gasoline
Any time energy is generated, the process can be evaluated from an E = mc2 perspective.
Today we use the nuclear energy to generate useful heat and electricity. In 2011 nuclear power provided 10% of the world’s electricity. In 2007, the IAEA reported there were 439 nuclear power reactors in operation in the world, operating in 31 countries. They produce base-load electricity 24/7 without emitting any pollutants into the atmosphere (this includes CO2).
This formule describes equivalence of mass and energy.
What that means? If the nuclear energy is generated (splitting atoms, nuclear fussion), a small amount of mass transforms into the pure energy (such as kinetic energy, thermal energy, or radiant energy).
Example:
The energy equivalent of one gram (1/1000 of a kilogram) of mass is equivalent to:
89.9 terajoules
25.0 million kilowatt-hours (≈ 25 GW·h)
21.5 billion kilocalories (≈ 21 Tcal)
85.2 billion BTUs
or to the energy released by combustion of the following:
21.5 kilotons of TNT-equivalent energy (≈ 21 kt)
568,000 US gallons of automotive gasoline
Any time energy is generated, the process can be evaluated from an E = mc2 perspective.
Today we use the nuclear energy to generate useful heat and electricity. In 2011 nuclear power provided 10% of the world’s electricity. In 2007, the IAEA reported there were 439 nuclear power reactors in operation in the world, operating in 31 countries. They produce base-load electricity 24/7 without emitting any pollutants into the atmosphere (this includes CO2).
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