Period 1 - Samantha Dileva <3 David de la Torre Nuclear Fusion
Nuclear fusion occurs during the process of a nuclear reaction in which two or more atomic nuclei collide at extreme velocity and fuse together to form a new and larger nucleus. The original mass of the combined nuclei involved in the collision is greater than the resulting mass of the larger newly formed nucleus. The nuclear reaction converts the missing mass into energy, which demonstrates Einstein's mass-energy equivalence formula E = mc2. Albert Einstein introduced his formula in 1905. During the 1930’s Einstein’s theories led scientist to realize that large amounts of energy can be obtained in nuclear reactions. Since the velocity of light, 186,000 miles per second or 299,792,458 meter per second, is a very large number Einstein’s formula suggests that a very small amount of mass can be converted into a very large amount on energy. The massive power of nuclear fusion led researchers towards the development of the hydrogen bomb in 1952.
Einstein's mass-energy formula helped cause scientist to realize that our sun is an example of a naturally occurring nuclear fusion reactor that fuses hydrogen atoms to form helium. At the sun’s core gravitational pressure and temperatures are high enough to force nuclear fusion. The process releases high-energy gamma ray photons. The Sun’s core temperature is approximately 15.7 million kelvin. The gravitational pressure at the core causes the density to be about 151,300 kilograms per cubic meter, or more than 13 times the density of solid lead. When hydrogen is heated to such temperatures it changes from a gas to plasma. While the hydrogen is in a plasma state the negatively charged electrons are separated from the positively charged atomic nuclei. There is a repelling electrostatic force between the positively charged nuclei which normally blocks them from getting close enough to permit fusion. However, there also is a strong force that normally holds the positively charged protons and neutrons (which have no charge), together in the nucleus. This strong force must be strong enough to contain the positively charged protons though they normally repel each other. However, the strong force is only strong at a very short distance, while the repelling force is effective at a farther distance. Therefore, the nuclei must collide at a very high velocity in order to get close enough to allow the strong force to overcome the outer weaker repelling force so that nuclear fusion can take place. Overall, since protons repel each other and fusion can only occur in the sun’s inner core, there are somewhat few nuclear reactions. The sun has plenty of hydrogen atoms. The sun is 92% hydrogen atoms and 7.8% helium atoms. It is estimated that total conversion of the sun's hydrogen would take more than ten billion years. Furthermore, the sun is said to be in hydrostatic equilibrium because the outward headed force caused by the hot gas and plasma are balanced by the inward headed gravitational force which is caused by the large mass.
Today scientists are attempting to harness nuclear fusion because it is considered renewable energy. Sea water contains abundant hydrogen in the form of deuterium (2H), which is an ideal fuel for nuclear fusion. The World Nuclear Association reports that power generated from nuclear fusion emits very little greenhouse gas compared to fossil fuels. Scientists around the world are working together to solve the complex scientific and engineering challenges that are keeping nuclear fusion from being a viable renewable energy source. So far, more energy is being used to operate a nuclear fusion reactor than has been able to be produced. Current technology has been attempting nuclear fusion using hydrogen in the form of deuterium (2H) and tritium (3H). Each deuterium and tritium nuclear fusion reaction produces 17.6 MeV. Deuterium is found naturally in seawater at about 30 grams per cubic meter. This means it is readily available and more abundant than most alternate energy sources. On the other hand Tritium, produced by cosmic rays, is not readily available and it is radioactive, with a half-life of around 12.5 years. Using Lithium in a conventional nuclear fusion reactor tritium can be made. Lithium is easily found in the earth’s crust (30 parts per million). There is also a small concentration available in sea water.
While the sun’s gravitational force provides an ideal condition for fusion, on earth it is extremely difficult to reach 100 million degrees Celsius. Furthermore it is difficult to keep a high concentration of hydrogen plasma confined long enough to cause the fusion to take place so that it can release energy. Scientist hope to create a nuclear reactor that will reach ignition and will be self-sustaining. This will require the reactor to produce enough fusion events so that the process creates its own heat source and a chain reaction. When it begins to generate enough of its own heat, then the energy generated will finally exceed the energy used to start the nuclear fusion. In this way the process will finally become productive and cost effective. After ignition is achieved and the process is underway fuel will be added to keep the process working. So far scientists are mostly experimenting with two kinds of nuclear fusion reactors :magnetic confinement (MFE) and fusion by inertial confinement (ICF). The MFE system uses powerful magnetic fields to trap the plasma, while the ICF system tries to compress hydrogen by smashing it with powerful lasers or particle beams. International Thermonuclear Experimental Reactor (ITER) located in France has been under construction since 2008 and is expected to be completed in 2018. It will be a tokamak design (doughnut shaped) using magnetic confinement to hopefully produce 500MW with an input of only 50MW. It is hoped to become the first commercially successful nuclear fusion power reactor. ITER’s tokamak magnetic confinement reactor will cause the plasma to be contained inside a doughnut-shaped vacuum vessel guided and surrounded with powerful magnetic fields. The fuel is a combination of deuterium and tritium nuclei, that will be heated to temperatures above 150 degrees Celsius so that it changes from a gas to plasma. Strong magnetic fields will keep the plasma from losing heat by interacting with the walls of the container. This will be done by using superconducting coils around the container and by applying electric current directly through the plasma. In the 1970's, scientists began experimenting with powerful laser beams to compress and heat the hydrogen isotopes to the point of fusion, using a method called inertial confinement fusion, or ICF. ICF uses powerful beams of laser light pointed at a small pellet or small balloon containing deuterium and tritium. The extremely rapid heating, caused by the lasers, of the outer layer of the target pellet, cause the pellet to explode along the outer crust. This explosion causes the remaining inner portion of the target to implode. The powerful and rapid compression of the fuel inside the capsule and the shock wave, further heat the fuel. The core of the fuel is supposed to begin a self-sustaining burn, the ignition. Nova is the name of the second generation laser driven ICF system located at Lawrence Livermore Laboratories. Using lasers ten times more powerful than earlier models, it will attempt to reach a breakeven point. That is when the energy spent is equal to energy released. Nova will focus 100,000 joules of energy during one nanosecond on a 1 mm diameter target area. So far Nova has not reached ignition.
The energy released through nuclear fusion is about three to four times greater than the energy released from nuclear fission. Fusion fuels provide little environmental pollution and the supply of fuel is almost endless. Currently the world is looking forward to the success of the International Thermonuclear Experimental Reactor.
Helium Atom
Basic Fusion Using Deuterium (2H) and Tritium (3H)
Einstein’s 1905 formula.
A Magnetic Confinement Reactor, MCF
ITER, The World's Largest Planned Tokamak MCF
Proton-Proton Chain (the sun's nuclear fusion)
Inertial Confinement Fusion, ICF
Nova laser at Lawrence Livermore Laboratories
Repelling Force of Positively Charged Deuterium (2H) and Tritium (3H)
Samantha Dileva <3
David de la Torre
Nuclear Fusion
Nuclear fusion occurs during the process of a nuclear reaction in which two or more atomic nuclei collide at extreme velocity and fuse together to form a new and larger nucleus. The original mass of the combined nuclei involved in the collision is greater than the resulting mass of the larger newly formed nucleus. The nuclear reaction converts the missing mass into energy, which demonstrates Einstein's mass-energy equivalence formula E = mc2. Albert Einstein introduced his formula in 1905. During the 1930’s Einstein’s theories led scientist to realize that large amounts of energy can be obtained in nuclear reactions. Since the velocity of light, 186,000 miles per second or 299,792,458 meter per second, is a very large number Einstein’s formula suggests that a very small amount of mass can be converted into a very large amount on energy. The massive power of nuclear fusion led researchers towards the development of the hydrogen bomb in 1952.
Einstein's mass-energy formula helped cause scientist to realize that our sun is an example of a naturally occurring nuclear fusion reactor that fuses hydrogen atoms to form helium. At the sun’s core gravitational pressure and temperatures are high enough to force nuclear fusion. The process releases high-energy gamma ray photons. The Sun’s core temperature is approximately 15.7 million kelvin. The gravitational pressure at the core causes the density to be about 151,300 kilograms per cubic meter, or more than 13 times the density of solid lead. When hydrogen is heated to such temperatures it changes from a gas to plasma. While the hydrogen is in a plasma state the negatively charged electrons are separated from the positively charged atomic nuclei. There is a repelling electrostatic force between the positively charged nuclei which normally blocks them from getting close enough to permit fusion. However, there also is a strong force that normally holds the positively charged protons and neutrons (which have no charge), together in the nucleus. This strong force must be strong enough to contain the positively charged protons though they normally repel each other. However, the strong force is only strong at a very short distance, while the repelling force is effective at a farther distance. Therefore, the nuclei must collide at a very high velocity in order to get close enough to allow the strong force to overcome the outer weaker repelling force so that nuclear fusion can take place. Overall, since protons repel each other and fusion can only occur in the sun’s inner core, there are somewhat few nuclear reactions. The sun has plenty of hydrogen atoms. The sun is 92% hydrogen atoms and 7.8% helium atoms. It is estimated that total conversion of the sun's hydrogen would take more than ten billion years. Furthermore, the sun is said to be in hydrostatic equilibrium because the outward headed force caused by the hot gas and plasma are balanced by the inward headed gravitational force which is caused by the large mass.
Today scientists are attempting to harness nuclear fusion because it is considered renewable energy. Sea water contains abundant hydrogen in the form of deuterium (2H), which is an ideal fuel for nuclear fusion. The World Nuclear Association reports that power generated from nuclear fusion emits very little greenhouse gas compared to fossil fuels. Scientists around the world are working together to solve the complex scientific and engineering challenges that are keeping nuclear fusion from being a viable renewable energy source. So far, more energy is being used to operate a nuclear fusion reactor than has been able to be produced. Current technology has been attempting nuclear fusion using hydrogen in the form of deuterium (2H) and tritium (3H). Each deuterium and tritium nuclear fusion reaction produces 17.6 MeV. Deuterium is found naturally in seawater at about 30 grams per cubic meter. This means it is readily available and more abundant than most alternate energy sources. On the other hand Tritium, produced by cosmic rays, is not readily available and it is radioactive, with a half-life of around 12.5 years. Using Lithium in a conventional nuclear fusion reactor tritium can be made. Lithium is easily found in the earth’s crust (30 parts per million). There is also a small concentration available in sea water.
While the sun’s gravitational force provides an ideal condition for fusion, on earth it is extremely difficult to reach 100 million degrees Celsius. Furthermore it is difficult to keep a high concentration of hydrogen plasma confined long enough to cause the fusion to take place so that it can release energy. Scientist hope to create a nuclear reactor that will reach ignition and will be self-sustaining. This will require the reactor to produce enough fusion events so that the process creates its own heat source and a chain reaction. When it begins to generate enough of its own heat, then the energy generated will finally exceed the energy used to start the nuclear fusion. In this way the process will finally become productive and cost effective. After ignition is achieved and the process is underway fuel will be added to keep the process working. So far scientists are mostly experimenting with two kinds of nuclear fusion reactors :magnetic confinement (MFE) and fusion by inertial confinement (ICF). The MFE system uses powerful magnetic fields to trap the plasma, while the ICF system tries to compress hydrogen by smashing it with powerful lasers or particle beams. International Thermonuclear Experimental Reactor (ITER) located in France has been under construction since 2008 and is expected to be completed in 2018. It will be a tokamak design (doughnut shaped) using magnetic confinement to hopefully produce 500MW with an input of only 50MW. It is hoped to become the first commercially successful nuclear fusion power reactor. ITER’s tokamak magnetic confinement reactor will cause the plasma to be contained inside a doughnut-shaped vacuum vessel guided and surrounded with powerful magnetic fields. The fuel is a combination of deuterium and tritium nuclei, that will be heated to temperatures above 150 degrees Celsius so that it changes from a gas to plasma. Strong magnetic fields will keep the plasma from losing heat by interacting with the walls of the container. This will be done by using superconducting coils around the container and by applying electric current directly through the plasma. In the 1970's, scientists began experimenting with powerful laser beams to compress and heat the hydrogen isotopes to the point of fusion, using a method called inertial confinement fusion, or ICF. ICF uses powerful beams of laser light pointed at a small pellet or small balloon containing deuterium and tritium. The extremely rapid heating, caused by the lasers, of the outer layer of the target pellet, cause the pellet to explode along the outer crust. This explosion causes the remaining inner portion of the target to implode. The powerful and rapid compression of the fuel inside the capsule and the shock wave, further heat the fuel. The core of the fuel is supposed to begin a self-sustaining burn, the ignition. Nova is the name of the second generation laser driven ICF system located at Lawrence Livermore Laboratories. Using lasers ten times more powerful than earlier models, it will attempt to reach a breakeven point. That is when the energy spent is equal to energy released. Nova will focus 100,000 joules of energy during one nanosecond on a 1 mm diameter target area. So far Nova has not reached ignition.
The energy released through nuclear fusion is about three to four times greater than the energy released from nuclear fission. Fusion fuels provide little environmental pollution and the supply of fuel is almost endless. Currently the world is looking forward to the success of the International Thermonuclear Experimental Reactor.
Basic Fusion Using Deuterium (2H) and Tritium (3H)
Einstein’s 1905 formula.
A Magnetic Confinement Reactor, MCF
ITER, The World's Largest Planned Tokamak MCF
Proton-Proton Chain (the sun's nuclear fusion)
Inertial Confinement Fusion, ICF
Nova laser at Lawrence Livermore Laboratories
Repelling Force of Positively Charged Deuterium (2H) and Tritium (3H)
Works Cited
"Hot Fusion." - Environmentalresearchweb. IOP, n.d. Web. 22 Dec. 2013. http://environmentalresearchweb.org/cws/article/opinion/43980.
"How ICF Works." Lawrence Livermore National Laboratory. Lawrence Livermore National Laboratory, n.d. Web. 23 Dec. 2013. https://lasers.llnl.gov/programs/nic/icf/how_icf_works.php.
"Inertial Confinement Fusion." Inertial Confinement Fusion. N.p., n.d. Web. 27 Dec. 2013. http://hyperphysics.phy-astr.gsu.edu/hbase/nucene/finert.html.
"Information Library." WNA. World Nuclear Association, n.d. Web. 23 Dec. 2013. http://www.world-nuclear.org/Information-Library/.
"ITER - the Way to New Energy." ITER - the Way to New Energy. N.p., n.d. Web. 28 Dec. 2013. http://www.iter.org/mach.
"NASA's Cosmos." NASA's Cosmos. Professor Kenneth R. Lang, Tufts University, n.d. Web. 23 Dec. 2013. http://ase.tufts.edu/cosmos/index.asp.
"Nuclear Fusion." Fusion. Georgia Perimeter College, n.d. Web. 28 Dec. 2013. http://facstaff.gpc.edu/~fbuls/ast102/part1/fusion.htm.
"Stars." Stars. NASA's Goddard Space Flight Center., n.d. Web. 23 Dec. 2013. <http://imagine.gsfc.nasa.gov/docs/science/know_l2/stars.html>.