Nuclear fusion Definition and 125 Discussions

Nuclear fusion is a reaction in which two or more atomic nuclei are combined to form one or more different atomic nuclei and subatomic particles (neutrons or protons). The difference in mass between the reactants and products is manifested as either the release or the absorption of energy. This difference in mass arises due to the difference in atomic binding energy between the nuclei before and after the reaction. Fusion is the process that powers active or main sequence stars and other high-magnitude stars, where large amounts of energy are released.
A fusion process that produces nuclei lighter than iron-56 or nickel-62 will generally release energy. These elements have relatively small mass per nucleon and large binding energy per nucleon. Fusion of nuclei lighter than these releases energy (an exothermic process), while fusion of heavier nuclei results in energy retained by the product nucleons, and the resulting reaction is endothermic. The opposite is true for the reverse process, nuclear fission. This means that the lighter elements, such as hydrogen and helium, are in general more fusible; while the heavier elements, such as uranium, thorium and plutonium, are more fissionable. The extreme astrophysical event of a supernova can produce enough energy to fuse nuclei into elements heavier than iron.
In 1920, Arthur Eddington suggested hydrogen-helium fusion could be the primary source of stellar energy. Quantum tunneling was discovered by Friedrich Hund in 1929, and shortly afterwards Robert Atkinson and Fritz Houtermans used the measured masses of light elements to show that large amounts of energy could be released by fusing small nuclei. Building on the early experiments in artificial nuclear transmutation by Patrick Blackett, laboratory fusion of hydrogen isotopes was accomplished by Mark Oliphant in 1932. In the remainder of that decade, the theory of the main cycle of nuclear fusion in stars was worked out by Hans Bethe. Research into fusion for military purposes began in the early 1940s as part of the Manhattan Project. Self-sustaining nuclear fusion was first carried out on 1 November 1952, in the Ivy Mike hydrogen (thermonuclear) bomb test.
Research into developing controlled fusion inside fusion reactors has been ongoing since the 1940s, but the technology is still in its development phase.

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  1. D

    Nuclear fusion energy calculations

    Me again! For a sci-fi story I'm working on, I've created a sci-fi technology called an Aneutronic Triple Alpha Fusion Reactor. It works via aneutronic fusion, in this case, fusing Deuterium with Helium 3, but it also mimics the triple alpha process found within stars to maximise fuel use...
  2. T

    B Where do the electrons go? (in stellar nuclear fusion)

    I have to give a presentation about natural Radiation and I am very happy about it because it includes Astrophysics. I want to explain to my audience how the stars produce cosmic rays. I thought about explaining to them how nuclear fusion and that kind of stuff works but then I realized that I...
  3. Thomas Sturm

    B Amount of Plasma [g] in nuclear fusion designs

    Hi everyone, I am trying to figure out the following question: What is the typical mass of the plasma (in typical working configuration) in current nuclear fusion reactor designs? https://en.wikipedia.org/wiki/ITER: "...plasma volume of 840 cubic meters..." So all I need is the plasma density...
  4. cellist542

    Programs What is the best major or double major for Nuclear Fusion research?

    I might be interested in researching nuclear fusion reactors after college. What majors or double majors would be best suited for this career path? Physics, nuclear engineering, materials science, electrical engineering, mechanical engineering, etc?
  5. Javier Lopez

    A What is the key parameter in fusion: momentum or energy?

    The released products of a transmutation reaction (I say transmutation when 2 particles reacts to generate more than one) follows the conservation of kinetic energy law. Also particles moving in opposite direction can have equal speed one with respect the other than rather if one of them is...
  6. Jan Berkhout

    How is current induced in the plasma in a tokamak?

    For a Year 12 Assignment I have to do a seminar on how magnetic fields are involved with a certain topic. I chose nuclear fusion energy production and specifically the tokamak. I understand that a toroidal magnetic field is created when a current is sent through a solenoid wrapped in a torus...
  7. Ryan Doucette

    Nuclear Fusion: Electron Thermal Transport Terminology

    I am an undergrad physics major in my final semester currently taking Intro to Thermodynamics. As a final project, each student must choose a topic related to thermodynamics that is more advanced than what is covered in the curriculum and write a paper and present our findings to the class on...
  8. Arthur Rocha

    B Nuclear Fusion energy questions

    Hi guys, I have been reading about nuclear fusion and I have some doubts that I did not find the answer. I understand that the reactants are in a more energetic state than the products when the energy release occurs, however: *What triggers the release of energy? *Where does the released energy...
  9. Jam Smith

    B Nuclear fission

    http://physics.stackexchange.com/questions/249809/why-only-light-nuclei-are-able-to-undergo-nuclear-fusion-not-heavy-nuclei Can anyone please explain me - what is similar between Nuclear fission & Nuclear fusion? Why are only light nuclei able to undergo nuclear fusion, not heavy nuclei? I am a...
  10. chandrahas

    I Problem understanding crosssection

    I understand that the nuclear cross section determines the probability of fusion taking place. When I was talking to my friend he said that the cross section doesn't depend on anything but the particles and their energies. But I fail to understand this. For example, let us consider ionization. I...
  11. P

    B Dark matter stars?

    ok so this has been on my mind for a while. If the hotter a stars burn or flame the further it goes on the spectrum correct so what if it burned so hot it is literally invisible wouldent that be considered a dark matter then it's a dark matter sun
  12. UMath1

    Engineering Electrical vs Mechanical Engineering: Jobs, Demand, Roles

    I am a high school senior debating between these two majors. In high school, I enjoyed both Mechanics and E&M very much so its really tough for me to decide which of the two engineering fields I'll like more. Whichever field I pick, I am also planning to minor or double in Physics and Computer...
  13. J

    A Why 15 million K is sufficient for fusion in solar core?

    Wikipedia says that solar core has 15 millions of Kelvins ( https://en.wikipedia.org/wiki/Solar_core ), what translates into ~1.4 keV energy per degree of freedom. For nuclear fusion we need to take the two nuclei to distance of range of nuclear forces: ~1fm (...
  14. D

    B Can elements die?

    How could an element and all its atoms die? With nuclear fusion they combine atoms, so are they also making elements?...is it possible to make an element shooting the right number of p+,n, & e- and then contain it/save it for later?
  15. P

    Amount of energy generated from fusion

    Homework Statement Assuming that we could generate Australia's electricity from a fusion reactor, that converted hydrogen to iron and turned the energy into electricity with 100% efficiency, what mass of fuel would it use per year? You may assume that this fusion reaction converts 1% of the...
  16. Arubi Bushlee

    B Aneutronic Fusion Fuel?

    has anyone looked into the possibility of nuclear fusion without neutrons? it would make IEC fusion easier without all the neutrons running around making things radioactive and wearing them down. I am wondering if p-B11 (proton-boron11) fusion is really an aneutronic fuel. deuterium-Helium3...
  17. Arubi Bushlee

    What is the process of invention?

    I make no promises: I came up with this idea for a new kind of nuclear fusion reactor. I do not want to give off any clues to how it works so I am going to be as vague as possible. I think it could be a viable means to nuclear fusion becoming... well, breakeven. I have by no means tested it...
  18. S

    Particle accelerator based nuclear fusion?

    I do think that the idea I had recently and one that I have been pondering about since is something mundane. Specifically because its so simple. Yet its an abstract one that I would like to know more about it from someone who can take the time to think about it and write a paragraph or two. In...
  19. stevebd1

    7-X Stellarator

    Here's an interesting article (from the magazine Science) about the Wendelstein 7-X Stellarator which is due to be switched on at the end of the month- 'The bizarre reactor that might save nuclear fusion' http://www.sciencemag.org/content/350/6259/369.full Construction video-
  20. F

    MS in Plasma Physics (Nuclear Fusion) -- France or Germany?

    I am interested in applying plasma physics in nuclear fusion program in France or Germany . Both are good in this field , but where i can get good scholarships and i am from electrical engineering background so where i have better chance of getting admitted.
  21. luetm

    Harvesting Fusion Energy

    Hi I have a really weird idea that is robbing me of my sleep. One of the many problems with fusion seems to be how to harvest the energy released by the reaction efficiently. So as I was slowly drifting into sleep I was wondering, how we usually harvest energy from reactions, and the piston...
  22. C

    Nuclear fusion using miniature optical particle accelerator?

    Greetings I am not a physicist myself, so please forgive me, if my question/proposition will sound naif. I noticed some articles about accelerating electrons using laser and glass gratings: http://phys.org/news/2013-09-chip.html http://phys.org/news/2013-10-particles-compact-particle.html...
  23. Zeedr

    Is this idea remotely possible in the distant future?

    Hello, I was just brainstorming for futuristic inventions with context for a sci-fi, high fidelity game (because I'm too cool to revise for exams) - and I thought of one, but my physics and engineering knowledge is at best sketchy when it comes to gravity and nuclear fusion combinations, I was...
  24. U

    Nuclear Decay - Semi Empirical Formula

    Homework Statement (a) What processes changes atomic number by 1? What are the favourable conditions? How do you tell a neutrino is involved? How can we use this to understand the mass of this particle? (b) Use semi empirical mass formula to explain why odd-odd isobars are unlikely, while...
  25. Andropov

    D-shape cross-section of plasma in fusion reactors

    I was curious about why the plasma inside a modern fusion reactor (ITER, DIII-D) is modeled with a D-shaped cross section. From what I've read, it is more stable that way, but WHY is it more stable than a similar plasma flow with a circular cross-section? Thanks in advance (and sorry if I...
  26. Evanish

    NASA An idea for a Pu-238 replacement for NASA space missions

    So I was reading this article about http://www.wired.com/2013/09/plutonium-238-problem/all/ and it got me thinking about possible substitutes. This is what I came up with. You make thin sheets of beryllium mixed with some kind of alpha particle emitter. You also make thin sheets of some...
  27. K

    How to prepare for R&D in nuclear power?

    What courses can I pursue after my undergrad education that will enable me to work on next gen nuclear technologies? What kinds of people work in these areas and what career paths do they choose? I've read a lot about the different kinds of people working on Gen 4 reactors(LFTRs, TWRs) and...
  28. J

    Lockheed SkunkWorks Fusion plan

    In the news today, several articles about Lockheed's ambitious five or ten year plan. eg this one from the Washington Post. http://www.washingtonpost.com/news/capital-business/wp/2014/10/15/nuclear-fusion-energy-in-a-decade-lockheed-martin-is-betting-on-it/ This one from Aviation Week...
  29. FuturePhysicist

    Fusion Reactor Power Supply.

    Hello, I'm 15 and very interested in physics. I'm building a safe nuclear fusion reactor as a science project. (I know how to safely handle high voltage and radiation) I have a question about the power supply. First off, I know that fusion takes around 40 Kilo-volts and it needs to have a...
  30. PolywellGuy

    The Spectrum for a pure electron plasma

    Hello All, In this recent Navy publication, a team of researchers said they have discovered cusp confinement. This could be a major step towards fusion power. I am working on a write up of this publication. I am trying to understand their inferometry data. As far as I can tell, the...
  31. Q

    What should I major in to be a part of making nuclear fusion a viable energy source?

    I am a Senior in High School and I would like guidance in selecting a major. I've been most seriously considering Aeronautical, Mechanical, Chemical, and Materials engineering. Maybe Engineering Physics, I don't know too much about it though. Is nuclear engineering a major some places? What...
  32. D

    Post-Graduate Study for Career in Nuclear Fusion?

    Hi, I'm in my final year at an Australian high school and I plan on completing at Bachelors in Science Majoring in Physics as my undergraduate course. My career aspiration is one day work researching nuclear fusion, though I am happy to work with fission reactors, they're just not my first...
  33. J

    What fraction of the Sun’s total mass is lost during fusion?

    Homework Statement During fusion of hydrogen to helium, 4 billion kg of matter are converted to energy each second. What fraction of the Sun’s total mass is lost each year to this process? Homework Equations None. The Attempt at a Solution First: Convert how many seconds are there in a year 1...
  34. J

    Nuclear fusion finance plan rejected by EU Parliament

    http://www.bbc.co.uk/news/science-environment-12007965" [Broken] Can anyone shed any light on this? Will work on building ITER be delayed or postponed because of this wrangling? They are talking about absolutely huge amounts of money which is maybe politically unpalatable for many...
  35. J

    A layman's question about nuclear fusion

    Hi, I’m a hobbyist writer with a slight science fiction slant to my stories. Currently my work involves some reference to the much expected nuclear fusion power. I have been doing some research online, but since I’m not a physicist this naturally resulted in a number of questions. I’m not...
  36. D

    General consensus on Cold Fusion better known as Low Energy Nuclear Reactions LENR?

    General consensus on Cold Fusion better known as "Low Energy Nuclear Reactions" LENR? I was wondering for those that know. What is the general consensus on Cold Fusion which is actually not cold fusion at all but "Low Energy Nuclear Reactions" LENR? The term cold fusion was made by the media...
  37. A

    Nuclear Fusion for electricty, boils water and moves a turbine? Or how it works?

    Hello. I know that most fission reactors boils water to move a turbine like this one. Is the same for a future nuclear fusion power plant, produce heat and boil water? Some light about this please.
  38. V

    Nuclear fusion and the end of energy problems claim

    Nuclear fusion and the "end of energy problems" claim Hi, Is it me, or does the following claim seem naive? "If we can achieve fusion here on earth, then the world's energy problem will be solved." As I understand it, our energy problems are more to do with greed and waste than...
  39. H

    Nuclear fusion and strong force

    I want to know the work of strong force during fusion of two atoms (say hydrogen), It is known that atoms need to get close enough to fuse but what does strong force especially "color charges" or "gluon" perform which causes fusion?
  40. P

    Nuclear fusion

    Homework Statement How much energy, in joules, is released when one mole of helium-4 nuclei is formed from its individual protons and neutrons? Homework Equations 2p + 2n ----> He-4 (p is proton n is neutron) The Attempt at a Solution Book sucks at explaining...
  41. R

    Ph.D in Nuclear Fusion power?

    Hello, I'm a Mechanical Engineering grad with a M.S. in Controls and Dynamics and have been working for a year. I was originally set to get a Ph.D in Controls but I kind of got burnt out on being a student and settled for a M.S. (would have just left but it took so long to find a job I ended...
  42. J

    Nuclear fusion

    Homework Statement For my essay on nuclear fission and fusion, I have to discuss some experimental evidence for nuclear fusion. I also need to find info about scientist that are responsible for developing the theory behind nuclear fusion. I am having trouble find info on these aspect. Any...
  43. M

    Nuclear Fission/Fusion

    Hi forums .. i got 2 questions, i got the main idea how to solve them but i still need some help. 1) Use the following fusion reaction to determine the amount of mass that is converted to energy. 2/1 H + 3/1 H  4/2 He + 1/0 n + 17.6 MeV Solution . mh2 = 2.014102 mh3=...
  44. K

    Potential barrier in nuclear fusion

    Homework Statement To calculate the height of the potential barrier for a head on collision between two deuterons given that each deuteron is a sphere of radius R Homework Equations Potential of the first deuteron at a distance of 2R from it =V = ke/2R where k = 9 * 10^9 , e= 1.6 *...
  45. D

    Nuclear Fusion Question?

    Hi all, I've been given an assignment to calculate the temperature increase of the fusion reactor walls in some theoretical event. It is a 30keV plasma energy in which the heat of the entire plamsa is instantaneously dropped on the wall. I can calculate volume of the wall and have the given...
  46. L

    D+D Nuclear Fusion Reactors

    Do you think D+D Nuclear Fusion will be possible within the next 50 or 60 years? Although the Z machine reportedly reached temperatures of over 2,000,000,000 Degrees (F), I doubt we will be able to output enough energy and pressure to make a self-sustaining D+D fusion reaction anytime within the...
  47. W

    Nuclear fusion

    Is the reason why the energy liberating fustion process ends with uranium(more precisely Iron) is that uranium's bindind energy per nucleon begins to decrease and hence will absorb energy rather than emit it, and thus is not self sustaining? Thanks in Advance
  48. D

    Undergraduate Major for Career in Nuclear Fusion

    Hello. I am currently a senior in high school. I am currently taking AP Physics C and will be through calc III/diff eq by the time i graduate. I am interested in going into nuclear engineering but i do not just want to work at some power plant the rest of my life. I am interested in theorhetical...
  49. T

    Nuclear fusion using plasma Part 2

    I seem to be having a problem adding a reply to the end of the previous thread so I am starting a new one! Thanks for everyone replying. A couple of points. The first is that nobody seems to have tried two end-on plasmas directed at each other. A dense pair of plasmas fired at each other...
  50. T

    Nuclear fusion using a plasma jet

    As per a previous thread, if you fire two plasma jets of deuterium at each other at high enough relative velocity, the deuterons would collide and fuse into helium. Does anyone know what is the relative velocity in kilometers per hour necessary for deuterons hitting each other head on to fuse...
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