(55173017) Mee75 Nuclear Power Plant-unit1
Content
MEE75 NUCLEAR POWER PLANT UNIT-1 NUCLEAR FUELS 1.What is nuclear fuels? Nuclear fuel is a material that can be 'burned' by nuclear fission or fusion to derive nuclear energy. Nuclear fuel can refer to the fuel itself, or to physical objects (for example bundles composed of fuel rods) composed of the fuel material, mixed with structural, neutron moderating, or neutron reflecting materials. Nuclear fuel is any material that can be consumed to derive nuclear energy. The most common type of nuclear fuel is fissile elements that can be made to undergo nuclear fission chain reactions in a nuclear reactor The most common nuclear fuels are 235U and 239Pu. Not all nuclear fuels are used in fission chain reactions 2.What is nuclear reaction? Most nuclear fuels contain heavy fissile elements that are capable of nuclear fission. When these fuels are struck by neutrons, they are in turn capable of emitting neutrons when they break apart. This makes possible a self-sustaining chain reaction that releases energy with a controlled rate in a nuclear reactor or with a very rapid uncontrolled rate in anuclear weapon. 3.What is Nuclear Fusion? The most common fissile nuclear fuels are uranium-235 (235U) and plutonium-239 (239Pu). The actions of mining, refining, purifying, using, and ultimately disposing of nuclear fuel together make up the nuclear fuel cycle. Not all types of nuclear fuels create power from nuclear fission. Plutonium-238 and some other elements are used to produce small amounts of nuclear power by radioactive decay in radioisotope thermoelectric generators and other types of atomic batteries. Also, light nuclides such as tritium (3H) can be used as fuel for nuclear fusion. 4.What is nuclear Fission? When a neutron strikes an atom of uranium, the uranium splits ingto two lighter atoms and releases heat simultaneously. Fission of heavy elements is an exothermic reaction which can release large amounts of energy both as electromagnetic radiation and as kinetic energy of the fragments 5.What is Nuclear Chain reaction?
A chain reaction refers to a process in which neutrons released in fission produce an
additional fission in at least one further nucleus. This nucleus in turn produces
C.MARIA ANTOINE PUSHPARAJ/AP/DEPARTMENT OF MECHANICAL ENGINEERING
neutrons, and the process repeats. If the process is controlled it is used for nuclear power or if uncontrolled it is used for nuclear weapons
U235 + n → fission + 2 or 3 n + 200 MeV
If each neutron releases two more neutrons, then the number of fissions doubles each
generation. In that case, in 10 generations there are 1,024 fissions and in 80 generations about 6 x 10 23 (a mole) fissions. 6.Give a detailed study about nuclear reator? NUCLEAR REACTOR A nuclear reactor is a device in which nuclear chain reactions are initiated, controlled, and sustained at a steady rate, as opposed to a nuclear bomb, in which the chain reaction occurs in a fraction of a second and is uncontrolled causing an explotion.
C.MARIA ANTOINE PUSHPARAJ/AP/DEPARTMENT OF MECHANICAL ENGINEERING
6.Define the nuclear fertile ? 1. The fissionable nucleides such as U-235 & Pu-239 are called fissile nucleides. 2. The non-fissionable nucleides such as U-238 & Th-232 are called fertile nucleides. 7.Explain the fissile chaaacteristics? In general, most actinide isotopes with an odd neutron number are fissile. Most nuclear fuels have an odd atomic mass number (A = Z + N = the total number of nucleons), and an even atomic number Z. This implies an odd number of neutrons. Isotopes with an odd number of neutrons gain an extra 1 to 2 MeV of energy from absorbing an extra neutron, from the pairing effect which favors even numbers of both neutrons and protons. This energy is enough to supply the needed extra energy for fission by slower neutrons, which is important for making fissionable isotopes also fissile What is nuclear chain reaction? A nuclear chain reaction occurs when one nuclear reaction causes an average of one or more nuclear reactions, thus leading to a self-propagating series of these reactions. The specific nuclear reaction may be the fission of heavy isotopes (e.g. 235U) or the fusion of light isotopes (e.g. 2H and 3H). The nuclear chain reaction releases several million times more energy per reaction than any chemical reaction.
C.MARIA ANTOINE PUSHPARAJ/AP/DEPARTMENT OF MECHANICAL ENGINEERING
What is fission chain reaction? Fission chain reactions occur because of interactions between neutrons and fissile isotopes (such as 235U). The chain reaction requires both the release of neutrons from fissile isotopes undergoing nuclear fission and the subsequent absorption of some of these neutrons in fissile isotopes. When an atom undergoes nuclear fission, a few neutrons (the exact number depends on several factors) are ejected from the reaction. These free neutrons will then interact with the surrounding medium, and if more fissile fuel is present, some may be absorbed and cause more fissions. Thus, the cycle repeats to give a reaction that is self-sustaining. Nuclear power plants operate by precisely controlling the rate at which nuclear reactions occur, and that control is maintained through the use of several redundant layers of safety measures. Moreover, the materials in a nuclear reactor core and the uranium enrichment level make a nuclear explosion impossible, even if all safety measures failed. On the other hand, nuclear weaponsare specifically engineered to produce a reaction that is so fast and intense it cannot be controlled after it has started. When properly designed, this uncontrolled reaction can lead to an explosive energy release What is nuclear fission fuels? Nuclear fission weapons must use an extremely high quality, highly-enriched fuel exceeding the critical size and geometry (critical mass) in order to obtain an explosive chain reaction. The fuel for a nuclear fission reactor is very different, usually consisting of a low-enriched oxide material (e.g. UO2).
C.MARIA ANTOINE PUSHPARAJ/AP/DEPARTMENT OF MECHANICAL ENGINEERING
What is fission reaction products? When a heavy atom undergoes nuclear fission it breaks into two or more fission fragments. Also, several free neutrons, gamma rays, and neutrinos are emitted, and a large amount of energy is released. The sum of the rest masses of the fission fragments and ejected neutrons is less than the sum of the rest masses of the original atom and incident neutron (of course the fission fragments are not at rest). The mass difference is accounted for in the release of energy according to the equation E=Δmc²: mass of released energy = Due to the extremely large value of the speed of light, c, a small decrease in mass is associated with a tremendous release of active energy (for example, the kinetic energy of the fission fragments). This energy (in the form of radiation and heat) carries the missing mass, when it leaves the reaction system (total mass, like total energy, is always conserved). While typical chemical reactions release energies on the order of a few eVs (e.g. the binding energy of the electron to hydrogen is 13.6 eV), nuclear fission reactions typically release energies on the order of hundreds of millions of eVs. Two typical fission reactions are shown below with average values of energy released and number of neutrons ejected:
[8 ]
[8]
Note that these equations are for fissions caused by slow-moving (thermal) neutrons. The average energy released and number of neutrons ejected is a function of the incident neutron speed.[8]Also, note that these equations exclude energy from neutrinos since these subatomic particles are extremely non-reactive and, therefore, rarely deposit their energy in the system What is neutron balance? In reactor statics we study time-independent phenomena Independence of time means that there is (or is assumed to be) neutron balance everywhere.
Therefore, all phenomena which involve neutrons must result altogether in equality
between neutron production and neutron loss (i.e., between neutron sources and sinks) at every position r in the reactor and for every neutron energy E. These phenomena are: Production of neutrons by induced fission Production of neutrons by sources independent of the neutron flux
C.MARIA ANTOINE PUSHPARAJ/AP/DEPARTMENT OF MECHANICAL ENGINEERING
Loss of neutrons by absorption Scattering of neutrons to other energies or directions of motion Leakage of neutrons into or out of each location in the reactor Neutron balance is expressed: essentially exactly, by the time-independent neutron-transport (Boltzmann) equation, and to some degree of approximation, by the neutron-diffusion equation What is fast fusion? Fast fission is fission that occurs when a heavy atom absorbs a high-energy neutron, called a fast neutron, and splits. Most fissionable materials need thermal neutrons, which move slower. What is thermalisation? In physics, thermalisation (in American English thermalization) is the process of particles reaching thermal equilibrium through mutual interaction. When a molecule absorbs energy, as in the technique of molecular fluorescence, the lifetime of the excited state is ~10−12 sec. Then it rapidly loses energy to the lowest level of the lowest excited state; this is called thermalization. In general the natural tendency of a system is towards a state of equipartition of energy or uniform temperature. This raises the system's entropy. Examples of thermalisation include: the achievement of equilibrium in a plasma the process undergone by high-energy neutrons as they lose energy by collision with a moderator.
What is nueutron capture? Neutron capture is a nuclear reaction in which an atomic nucleus and one or more neutrons collide and merge to form a heavier nucleus.[1] Since neutrons have no electric charge they can enter a nucleus more easily than positively chargedprotons, which are repelled electrostatically.[1] Neutron capture plays an important role in the cosmic nucleosynthesis of heavy elements. In stars it can proceed in two ways: as a rapid (r-process) or a slow process (s-process).[1] Nuclei of masses greater than 56 cannot be formed bythermonuclear reactions (i.e. by nuclear fusion), but can be formed by neutron capture.[1]
C.MARIA ANTOINE PUSHPARAJ/AP/DEPARTMENT OF MECHANICAL ENGINEERING
A chain reaction refers to a process in which neutrons released in fission produce an
additional fission in at least one further nucleus. This nucleus in turn produces
C.MARIA ANTOINE PUSHPARAJ/AP/DEPARTMENT OF MECHANICAL ENGINEERING
neutrons, and the process repeats. If the process is controlled it is used for nuclear power or if uncontrolled it is used for nuclear weapons
U235 + n → fission + 2 or 3 n + 200 MeV
If each neutron releases two more neutrons, then the number of fissions doubles each
generation. In that case, in 10 generations there are 1,024 fissions and in 80 generations about 6 x 10 23 (a mole) fissions. 6.Give a detailed study about nuclear reator? NUCLEAR REACTOR A nuclear reactor is a device in which nuclear chain reactions are initiated, controlled, and sustained at a steady rate, as opposed to a nuclear bomb, in which the chain reaction occurs in a fraction of a second and is uncontrolled causing an explotion.
C.MARIA ANTOINE PUSHPARAJ/AP/DEPARTMENT OF MECHANICAL ENGINEERING
6.Define the nuclear fertile ? 1. The fissionable nucleides such as U-235 & Pu-239 are called fissile nucleides. 2. The non-fissionable nucleides such as U-238 & Th-232 are called fertile nucleides. 7.Explain the fissile chaaacteristics? In general, most actinide isotopes with an odd neutron number are fissile. Most nuclear fuels have an odd atomic mass number (A = Z + N = the total number of nucleons), and an even atomic number Z. This implies an odd number of neutrons. Isotopes with an odd number of neutrons gain an extra 1 to 2 MeV of energy from absorbing an extra neutron, from the pairing effect which favors even numbers of both neutrons and protons. This energy is enough to supply the needed extra energy for fission by slower neutrons, which is important for making fissionable isotopes also fissile What is nuclear chain reaction? A nuclear chain reaction occurs when one nuclear reaction causes an average of one or more nuclear reactions, thus leading to a self-propagating series of these reactions. The specific nuclear reaction may be the fission of heavy isotopes (e.g. 235U) or the fusion of light isotopes (e.g. 2H and 3H). The nuclear chain reaction releases several million times more energy per reaction than any chemical reaction.
C.MARIA ANTOINE PUSHPARAJ/AP/DEPARTMENT OF MECHANICAL ENGINEERING
What is fission chain reaction? Fission chain reactions occur because of interactions between neutrons and fissile isotopes (such as 235U). The chain reaction requires both the release of neutrons from fissile isotopes undergoing nuclear fission and the subsequent absorption of some of these neutrons in fissile isotopes. When an atom undergoes nuclear fission, a few neutrons (the exact number depends on several factors) are ejected from the reaction. These free neutrons will then interact with the surrounding medium, and if more fissile fuel is present, some may be absorbed and cause more fissions. Thus, the cycle repeats to give a reaction that is self-sustaining. Nuclear power plants operate by precisely controlling the rate at which nuclear reactions occur, and that control is maintained through the use of several redundant layers of safety measures. Moreover, the materials in a nuclear reactor core and the uranium enrichment level make a nuclear explosion impossible, even if all safety measures failed. On the other hand, nuclear weaponsare specifically engineered to produce a reaction that is so fast and intense it cannot be controlled after it has started. When properly designed, this uncontrolled reaction can lead to an explosive energy release What is nuclear fission fuels? Nuclear fission weapons must use an extremely high quality, highly-enriched fuel exceeding the critical size and geometry (critical mass) in order to obtain an explosive chain reaction. The fuel for a nuclear fission reactor is very different, usually consisting of a low-enriched oxide material (e.g. UO2).
C.MARIA ANTOINE PUSHPARAJ/AP/DEPARTMENT OF MECHANICAL ENGINEERING
What is fission reaction products? When a heavy atom undergoes nuclear fission it breaks into two or more fission fragments. Also, several free neutrons, gamma rays, and neutrinos are emitted, and a large amount of energy is released. The sum of the rest masses of the fission fragments and ejected neutrons is less than the sum of the rest masses of the original atom and incident neutron (of course the fission fragments are not at rest). The mass difference is accounted for in the release of energy according to the equation E=Δmc²: mass of released energy = Due to the extremely large value of the speed of light, c, a small decrease in mass is associated with a tremendous release of active energy (for example, the kinetic energy of the fission fragments). This energy (in the form of radiation and heat) carries the missing mass, when it leaves the reaction system (total mass, like total energy, is always conserved). While typical chemical reactions release energies on the order of a few eVs (e.g. the binding energy of the electron to hydrogen is 13.6 eV), nuclear fission reactions typically release energies on the order of hundreds of millions of eVs. Two typical fission reactions are shown below with average values of energy released and number of neutrons ejected:
[8 ]
[8]
Note that these equations are for fissions caused by slow-moving (thermal) neutrons. The average energy released and number of neutrons ejected is a function of the incident neutron speed.[8]Also, note that these equations exclude energy from neutrinos since these subatomic particles are extremely non-reactive and, therefore, rarely deposit their energy in the system What is neutron balance? In reactor statics we study time-independent phenomena Independence of time means that there is (or is assumed to be) neutron balance everywhere.
Therefore, all phenomena which involve neutrons must result altogether in equality
between neutron production and neutron loss (i.e., between neutron sources and sinks) at every position r in the reactor and for every neutron energy E. These phenomena are: Production of neutrons by induced fission Production of neutrons by sources independent of the neutron flux
C.MARIA ANTOINE PUSHPARAJ/AP/DEPARTMENT OF MECHANICAL ENGINEERING
Loss of neutrons by absorption Scattering of neutrons to other energies or directions of motion Leakage of neutrons into or out of each location in the reactor Neutron balance is expressed: essentially exactly, by the time-independent neutron-transport (Boltzmann) equation, and to some degree of approximation, by the neutron-diffusion equation What is fast fusion? Fast fission is fission that occurs when a heavy atom absorbs a high-energy neutron, called a fast neutron, and splits. Most fissionable materials need thermal neutrons, which move slower. What is thermalisation? In physics, thermalisation (in American English thermalization) is the process of particles reaching thermal equilibrium through mutual interaction. When a molecule absorbs energy, as in the technique of molecular fluorescence, the lifetime of the excited state is ~10−12 sec. Then it rapidly loses energy to the lowest level of the lowest excited state; this is called thermalization. In general the natural tendency of a system is towards a state of equipartition of energy or uniform temperature. This raises the system's entropy. Examples of thermalisation include: the achievement of equilibrium in a plasma the process undergone by high-energy neutrons as they lose energy by collision with a moderator.
What is nueutron capture? Neutron capture is a nuclear reaction in which an atomic nucleus and one or more neutrons collide and merge to form a heavier nucleus.[1] Since neutrons have no electric charge they can enter a nucleus more easily than positively chargedprotons, which are repelled electrostatically.[1] Neutron capture plays an important role in the cosmic nucleosynthesis of heavy elements. In stars it can proceed in two ways: as a rapid (r-process) or a slow process (s-process).[1] Nuclei of masses greater than 56 cannot be formed bythermonuclear reactions (i.e. by nuclear fusion), but can be formed by neutron capture.[1]
C.MARIA ANTOINE PUSHPARAJ/AP/DEPARTMENT OF MECHANICAL ENGINEERING
