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--------------------- 2638 - FUSION - from stars to electricity ?
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- The fusion in the core of stars can be analyzed as simple hydrogen nuclei, which are protons, fusing together to create heavier elements. Each fusion process up to the element Iron releases some amount of energy.
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- Knowing how much energy our Sun puts out we can estimate the lifetime of our star, how long it will take to “burn up” all of this proton fuel.
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- How does fusion work in the stars? The end of this review to learn how fusion works on the planet Earth.
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- You look into the night sky and every shining star is a fusion reactor. It is so common, it can’t be that complicated. Well we have been seriously trying for 30 years and the breakeven point is still another 30 years away, maybe 50 to 100 years away. Fusion is simple, it is just not easy.
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- Here is how stars make fusion. Our Sun is a star that is a big ball of hydrogen. It originally collects as a ball of gas out of a cloud of hydrogen gas. Gravity constantly pulls matter into the densest center of gravity. Eventually it all condenses into a sphere of gas.
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- As the mass and gravity of the sphere grows the center of the sphere gets hotter and denser until the hydrogen gas ionizes into a plasma. Essentially this “plasma” is the nucleus of the hydrogen atoms separated from the negatively charged electrons. The electrons become free electrons and the nuclei remaining are positively charged protons.
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- The protons are heavier and get pulled into the center of gravity with immense density and temperature. Protons are like positive charges that repeal each other with the electromagnetic force. When the mass reaches 10% of the mass of our Sun the force of gravity can begin to overcome this electromagnetic force separating the protons. Nuclear fusion can begin.
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- The Sun is fusing these protons into Helium nuclei with its core temperature at 15,000,000 Centigrade. (The “surface temperature” of the Sun is 6,000 Centigrade). This same process occurs in all the stars.
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- However, if the mass of the stars is larger then fusion can continue beyond 2 Hydrogen , H-1, nuclei fusing into Helium nuclei,(He-2). When 3 protons fuse together they form Lithium, (Li-3). When 4 protons fuse together they form Beryllium, 5 - forms Boron, 6 - Carbon, 7 - Nitrogen, and this continues right up each of the heavier elements in the Periodic Table to 28 protons fuse to form Iron, Fe-28).
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- At the element 28 - Iron the fusion process does not release excess energy. Up until iron each element is slightly lighter than the sum of its parts( i.e.: protons). The excess mass is converted to energy according to E = mc^2. Elements heavier than Iron require the addition of energy in order to fuse rather the having an excess of energy.
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- When the core of the star becomes Iron no more excess energy is produced. The star collapses and rebounds into a massive explosion called a supernova. It is in this explosion that higher energies are reached and elements heavier than iron are produced.
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- The natural elements all the way up to 92 protons fusing to form Uranium, (U-92). 2 protons fuse into Helium, or, said in another way, 2 Hydrogen nuclei fuse into one Helium-2 nucleus. Or, to be more accurate to where we are heading, 4 protons fuse into a heavy isotope of Helium-4 which contains 2 protons and 2 neutrons with energy left over for 26.8 electron volts of sun power heading toward the surface of the Sun.
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- This sun power eventually leaves the surface with a total output power of 3.9 *10^26 watts. (That is 3.9 followed by 25 zeros). 8 minutes later it reaches the surface of Earth providing 1,300 watts of sun power on every square meter area.
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- Let’s go back to the core of the Sun and see step by step how this fusion actually happens:
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- (1) One proton fuses with a proton electron pair which is a neutron forming a Hydrogen isotope nucleus, called Deuterium. The Deuterium nucleus is one proton and one neutron. In addition to the H-2 Deuterium nucleus an anti-electron, an electron- neutrino, and 0.4 million electron volts of energy are produced. The anti-electron is also called a positron. The energy produced is abbreviated 0.4 MeV.
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- (2) This process is repeated with 2 other protons. The total reaction now contains: 2 H2. Deuterium nuclei + 2 anti electrons + 2 neutrinos and a total of 0.8 MeV.
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- (3) Both of these processes fuse with other neutrons creating a Hydrogen-3 isotope with one proton and 2 neutrons, plus Gamma Rays, and plus energy of 5.5MeV. For a total of 6.3 MeV, for the first fusion and 6.3 MeV again for the second fusion. Now the grand total of particles and energy in the fusion reaction is 2 protons and 4 neutrons in the 2 H-3 nuclei, 2 Gamma Rays and 11.8 MeV.
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- (4) When the above two processes fuse together the grand total of particles and energy released becomes 2 protons and 2 neutrons fuse to form Helium-4 and the 2 free neutrons decay to form 2 protons, and + 7 Gamma Rays, and + 2 neutrinos, and + releasing an additional 13.0 MeV of energy. This brings the total energy released to 24.8 MeV.
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- (5) The last step involves the 2 anti electrons that were produced which collide with 2 free electrons and annihilate each other into 4 Gamma Rays and 2.0 MeV of energy.
The total energy released from this 5 step process becomes 26.8 MeV.
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- Note that 4 protons were consumed for 26.8 / 4, or 6.7 MeV per proton. And, 2 protons were left over to repeat the process starting with step (1) again. This is referred to as a “chain reaction” that will continue over and over again until all the protons are consumed.
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- There are other fusion processes occurring in the dynamic plasma at the core of the Sun, but this is one of the fundamental fusion processes going on. If we used purely this process and assumed the Sun was a giant ball of protons how long would it shine before it ran out of protons to fuse?
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- The total mass of the Sun is 2.0 * 10^30 kilograms.
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- The mass of a single proton is 1.67 *10^-27 kilograms.
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- Their simple division tells us that there are 1.2*10^57 protons in the Sun. Of course, only the protons at the core of the Sun are at the pressures and temperatures necessary to cause a nuclear fusion reaction. Approximately 10% of the Sun’s mass can be considered the core. So, the core would contain 1.2 * 10^56 protons.
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- We know that the total energy output the these core protons are producing is 3.9 * 10^26 Watts. A Watt is a Joule of energy per second. There are 1.6022*10^19 electron-volts in one Joule of Energy. Therefore the Sun’s total output power in electron-volts per second is:
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---------------- 3.9 * 10^26 / 1. 6022 *10^-19 = 2.434*10^45 eV / second
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---------------- Sun’s energy = 2.434 * 10^39 MeV / second
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- We have calculated the energy contribution per proton to be 6.7 MeV. Again simple division tells us how many protons are being consumed each second in the core of the Sun.
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-------------- 2.434 * 10^39 MeV / second / 6.7 MeV = 3.6 * 10^38 protons / second
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- The Sun’s core has 1.2 * 10^56 protons and it is burning 3.6 * 10^38 protons each second, how many seconds can this last?
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--------------- 1.2 * 10^56 protons / 3.6 * 10^38 protons/ second = 3.3 * 10^17 seconds. There are 31,560,000 seconds in a year. So, that means that the Sun’s core can burn protons for about 10 billion years. This has been going on for about 5 billion years so the Sun has burned through about half of its supply of protons. We have another 5 billion years to go.
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- More massive stars than our Sun actually have shorter lives because they burn hotter and faster and go through their supply of protons with a shorter lifetime.
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------ 25 Solar Mass Star --------- 80,000 Luminosity of Sun ----- 3 million years
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------ 3 Solar Mass Star --------------- 60 Luminosity of Sun ----- 500 million years
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------ 1 Solar Mass Star ---------------- 1 Luminosity of Sun ----- 10,000 million years
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------ 1/2 Solar Mass Star ----------- 3 % Luminosity of Sun ----- 200,000 million years
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- Why Do We Not Have Fusion Reactors to Make Electricity?
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- Nearly all the electrical energy on Earth originates from the Sun. Wind, Oil, Gas, Hydro all get their energy coming from the bath of radiation we get from our nearest star. Because of the Conservation of Energy, all energy is conserved. We always have the same amount it is simply being converted from one form of energy to another.
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- So, why not solve our society’s energy problems by going directly to the source and creating our energy the same way the Sun does? How does the Sun get its energy? From Nuclear Fusion. Simply combining lighter elements into heavier elements.
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- In the Sun’s case combining 2 Hydrogen atom nuclei into one Helium atom nuclei. To state this even simpler, the Sun combines two single protons into one nucleus with two protons.
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- When fusion of two protons comes together to form Helium the combination is not quite as heavy, massive, as the individual protons that come from the Hydrogen nucleus. Remember, protons have a positive charge and like-charges repel each other.
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- The Strong Nuclear Force is needed to hold two protons together in the nucleus. When this nuclear reaction occurs a small amount of mass left over is converted directly to energy. The energy is in the form of Gamma Ray radiation, according to E = mc^2.
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- This Gamma Ray radiation occurs at the center of the Sun at a temperature of 28,000,000 F. Gamma Ray photons are high energy photons that have to bounce their way through layers of the Sun’s gas until finally reaching the surface at 10,000 degrees F. On average, it takes a single photon over 1 million years to make this journey to the surface.
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- To solve all our energy problems why can’t we duplicate this fusion process here on Earth? The process is simple, it is just not easy. Science can do it, but, it takes more energy to create and contain the 28,000,000 degree temperatures than we can retrieve from the nuclear fusion reaction it produces.
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- Science has been trying to economically produce energy using nuclear fusion for decades. Up until now the process to create fusion consumes more energy than the fusion produces. We have yet to reach a breakeven point, and, to be economical the process needs to be 20 to 30 times more efficient than just a breakeven.
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- To get nuclear fusion working for us many nations are spending research dollars building fusion reactors. The U.S. is spending $210 billion per year generating electric power. Some of that needs to go to research in building fusion reactors:
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- France is spending $20 billion in their fusion experiment that is scheduled to be completed by 2018.
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- Livermore, California is spending $3.5 billion to begin a fusion experiment by 2012. (See Review 1070).
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- Kirtland Air Force Base, part of Los Alamos National Labs, is investing $4 million dollars to create a breakeven fusion reactor. The Shiva Star facility at Kirtland does not have much money but it thinks it has a better idea. All three facilities are trying different approaches to producing nuclear fusion.
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- Overcoming the electromagnetic force with enough temperature and pressure forcing the nuclei to merge, or fuse, which creates a heavier element releasing nuclear energy requires immense gravity.
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- The Sun merges hundreds of millions of tons of Hydrogen into Helium every second at its core. And, it has been doing this for some 5 billion years. Every star in the night sky is doing the same thing in various degrees. Bigger stars have more gravity and fuse heavier elements. All star-energy comes from gravity compressing and heating lighter elements into heavier elements.
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- For nuclear fusion reactors on the planet the primary fuel used is Deuterium, which is a heavy isotope of Hydrogen, one proton and one neutron in the nucleus. Deuterium is abundant in seawater and easily available. Unlike fission reactors the dangerous radiation of the process’ by-products decays rapidly, within decades. Fission by-products carrying dangerous radiation can remain for centuries.
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- Fusion is definitely the way to go for producing energy. So, why is it so hard? Well, to start with it has to be hot, 27,000,000 degrees F, minimum. And, it also has to be under high pressure.
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- The center of the Sun is 200,000,000,000 atmospheres pressure. The melted plasma of ionized hydrogen, a soup of protons and free electrons, is so hot it would vaporize any material that we used to contain it. It takes tremendous force to overcome the electromagnetic force that is repelling 2 simple protons from fusing together.
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- We can not duplicate the mass and gravity of the Sun. What we really need is fusion in a beer can. They are trying to do that at Kirtland AFB using a technique called magnetized target fusion. The target is a 30 by 10 centimeter aluminum cylinder with 1 millimeter thick walls ( a beer can ).
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- A strong magnetic field is created to control the hot plasma of ionized Deuterium gas inside the can. The target-can is hit with 12 million amperes of electric current that will crush the can in 24 microseconds. The Deuterium nuclei fuse releasing nuclear energy that produce heat, to produce steam, to turn turbines and produce electricity.
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- The experimental machine to produce this enormous shot of electric current was originally designed as a weapon to shoot down incoming ballistic missiles by firing a burst of high energy plasma at the missile. It never succeeded as a weapon but it did destroy many experiments. It produces 5,000,000 joules of energy.
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- In this last decade they decided to alter the design to produce controlled fusion that would generate electricity instead of shoot down missiles. Current experiments are to get the machine to produce a fusion reaction that has a breakeven in “energy produced” versus “energy consumed“. It has not happened yet.
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- To become economically viable as an electric power plant in a community a fusion reactor must produce 30 times more energy out than what it consumes.
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- The experiment in France uses a machine that constructs its magnetic structure in the shape of a doughnut. It is called a “ Tokomak” and it is designed to produce 500,000,000 watts output with 50,000,000 watts input. This is a 10 times efficiency over breakeven.
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- Tokomak creates a doughnut shaped magnetic field that confines the ionized plasma into the center of the ring. The heating is “omic” heating, no different than the filament in an incandescent light bulb. The maximum temperature obtained to date is 20 to 30 million degrees.
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- Lawrence Livermore Lab has a machine using 192 lasers focused on a capsule of Deuterium and Tritium. The lasers focus 500,000,000,000 watts on a pellet the size of an aspirin. (See Review 1170 “Laser Ignition Fusion” for a detailed discussion of this process.)
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- The history of fusion started with the atomic bomb which eventually developed into the Hydrogen bomb in 1952.
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------------ In 1958 the reactor in Los Alamos first bottled Hydrogen Plasma in a magnetic field.
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------------ In 1968 a Soviet Tokomak produced a plasma raised to 1,000,000 degrees temperature.
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----------- In 1989 there were false claims within the science community that they had created cold fusion.
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---------- In 1997 the Tokomak in France generated 16 megawatts out with 24 megawatts input.
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----------- In 2002 there were false claims in the science community about bubble fusion being created using sound waves.
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----------- In 2009 Lawrence Livermore Labs first fusion ignition is scheduled to occur in 2012. (See Review 1070) The facility is called NIF, the National Ignition Facility, and it has achieved temperatures up to 10,600,000 F. Still not hot enough for fusion of the target Deuterium and Tritium into Helium. The temperature is measured by measuring the X-rays emitted by the exploding gold capsule that contains the target.
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--------- In 2011 the Energy Matter Conversion Corporation in Canada , EMC2, uses a proton-boron fuel which requires a higher temperature than Deuterium but converts directly to electricity without using boiling water to drive a generator.
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- It uses a electrostatic field to contain the positively charged ions. Its electromagnetic coils are arranged in a polyhedron of tubes. The configuration traps electrons in the middle. Ions are introduced to accelerate in a confined space until they create fusion power.
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- The polyhedron is essentially a large vacuum tube with spherical grids . The ions accelerate into the grid. Often the ions pass through the grid without a collision with other ions. Occasionally they collide. Hopefully fusion occurs.
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--------- In 2011 NIF has come up with another idea using their lasers. They will use a hybrid fusion-fission process. Lasers create fusion at the center of the reactor chamber. Neutrons emitted penetrate a blanket of Uranium that lines the chamber walls. Energy from the fission reactions in the Uranium multiple the chambers power by a factor of 4.
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- This process has the advantages of being able to use depleted uranium, or the spent fuel from the nuclear fission reactors now being used. Today’s fission reactors require Plutonium or Enriched Uranium which is used in nuclear weapons and dangerously radioactive.
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- These fission reactors consume only a few percent of the fissionable atoms in the Enriched Uranium. The hybrid fusion-fission reactor consumes 90% of the fissionable fuel. Less fuel is needed and less spent fuel is left behind.
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--------- In 2011 many technical problems remain to actually have a fusion electrical power plant in operation. We are still projecting a breakeven fusion reaction will happen soon. It will solve the World’s energy problems. When? God only knows.
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-------- 2013 - General Fusion in British Columbia is using a liquid metal lining with Tritium to create a fusion reaction. They are projecting a breakeven in 2013.
- The lucky ol’ Sun nothing to do but just roam round heaven all day.
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- February 28, 2020 1249 1250 2638
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--------------------- Saturday, February 29, 2020 --------------------
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