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With billions being spent on the effort, there should be a separate section about the ongoing research in that area. The article does mention this, but only embedded in sections on pure science.
Sean7phil ( talk) 19:55, 29 November 2009 (UTC)
I've read the article about Nuclear fusion (shouldn't that be either "nuclear fusion" or "Nuclear Fusion") and have faied utterly to understand where the energy actually comes from.
Perhaps a few sentences that make it more explicit would be helpful for those of us who aren't physics experts.
Also, as was mentioned elsewhere in this discussion, much of this is about how to generate power from nuclear fusion when it sould be about how fusion itself works.
Thanks
Dave
Davemenc 04:01, 27 November 2005 (UTC)
Smart White Boy 20:16, 20 April 2007 (UTC)Might I just add, the energy release can be explained in e=mc2. Energy equals lost mass times the square of the speed of light. This implies that a large amount of energy is held in a small amount of matter. That's all I wanted to add. Smart White Boy 20:16, 20 April 2007 (UTC)
I would question the stability argument. U235 is relatively stable. The fission products of U235 are both highly unstable, yet the reaction which produces them is exothermic. The paradigm of exothermic reactions leading to stable products belongs to chemistry. It does not necessarily apply to nuclear reactions, fission or fusion.
Perhaps the most lucid explanation (for the layman) is that the mass of an atom is not -quite- equal to the sum of the masses of its constituent parts. Thus, most instances of atoms being combined or split apart result in a small change of total mass. Since the sum of the system's mass and energy must be conserved, this 'mass defect' manifests iself as kinetic energy of the resultant particles. -- Anteaus ( talk) 22:34, 24 January 2008 (UTC)
Let me ask the question a different way: at the quantum level, why is fusion exothermic. It's easy to see this in fusion: you start out with a bunch of nucleons held together by strong force against electrostatic repulsion of protons. Add an extra neutron, and the nucleus is too big and splits. This releases some of the potential energy (from the repulsion). In additon, some of the gluons that were holding the nucleus together are released, that's a fair amount of mass available to convert to energy.
But to hold two or more protons together in a nucleus, you need to add gluons. That should require more energy to "generate" them. What mass is given up to make this happen? (Actually, I suspect it's more accurate to say that virtual gluons, spontaneously created and destroyed all the time, become actual when you put together a larger nucleus. Either way, you need energy to account for them. But then, my understanding of quantum chromodynamics is highly deficient. Even my knowledge of quantum electrodynamics is based on Feynman's popularization, Q.E.D.) Bgoldnyxnet ( talk) 18:18, 25 November 2008 (UTC)
Sigh. The main image has been replaced by an animation. Though I know we are supposed to say "hooray" for anyone who takes the time to make an animation, can I state that:
I'm sure the image took a long time to make, but is it really the best means of expressing this particular reaction? There are some things that animations are indispensable for and much better than static diagrams (the Two-stroke engine page is a great example of this—complicated movement of materials that must be explained in many frames = great for using an animation!). I'm not sure that simple nuclear reactions are among them (seeing the two atoms tediously run into each other presents no additional information, takes a lot longer). I personally think a diagram (like this one) is a lot clearer. It gets the same information content across in a much more clear and concise manner. In this particular case, the animation is even misleading in terms of the mechanism and amount of energy released. -- 98.217.8.46 ( talk) 02:01, 27 October 2008 (UTC)
Gamma + H2 --> p + n
n + H2 -->H3 + E1
H3 -> He3 + e-
He3 + n --> He4 + E2
147.236.34.10 ( talk) 11:47, 17 February 2009 (UTC)vicli2@rambler.ru
i see your point... maybe we should put the animation on a seprate page and create a link 'click here for an animation' or something. Jthekid15 ( talk) 09:55, 22 January 2014 (UTC)
the overview claims that tokamaks have demonstrated break-even. I don't recall reading this (I didn't think any reactor designs had yet actually accomplished break-even) and a quick googling turns up lots of discussions about potential break-even designs but no break-even.
the overview also makes it sound like ITER is going to be a working model for generating energy, that generating energy from fusion is right around the corner. my understanding is that neither of these things are actually considered to be true except by those who are financially involved in ITER.
it could use a little sourcing. especially given how many contrary opinions there are about whether we should expect fusion power anytime soon. -- 98.217.14.211 ( talk) 01:56, 5 April 2009 (UTC)
Tokamaks have not demonstrated break-even. ITER is designed to do so. ITER is not designed to be a 'commercial-style' demonstration plant, that is planned for the next generation reactor, DEMO. http://www.iter.org/sci/beyonditer 2001:630:12:10D0:2CB4:9415:E385:C14D ( talk) 15:19, 19 July 2013 (UTC)
It may be possible to reduce the temperature requirement for plasma formation by inducing temporary dipoles in the deuterium and tritium gas via microwave radiation. This is the same theory behind the formation of ball lightning and can be easily replicated. The modifications would be minimal, and plasma damage to the inner wall would be less extensive. —Preceding unsigned comment added by 66.66.118.233 ( talk) 18:45, 8 June 2009 (UTC)
The following (Overview, end of paragraph 3) is not a sentence, but fragment lacking a verb: "However, the creation of workable designs for a reactor which will deliver ten times more fusion energy than the amount needed to heat up plasma to required temperatures (see ITER which is scheduled to be operational in 2018)." --RDK
In the "Nuclear fusion in stars" section, the sentence "The net result is the fusion of four protons into one alpha particle, with the release of two positrons, two neutrinos (which changes two of the protons into neutrons), and energy" should have its parenthetical clause moved to follow "positrons" rather than "neutrinos", in order to avoid giving a mistaken impression. Revised version "The net result is the fusion of four protons into one alpha particle, with the release of two positrons (which changes two of the protons into neutrons), two neutrinos, and energy" would more appropriately signal that it is the release of charged positrons, not neutral neutrinos, which is associated with the proton-to-neutron changes. 69.95.141.252 ( talk) 02:24, 14 September 2015 (UTC)
By the way, the sentence as written vaguely implies that the Sun generates positrons by this process. Of course it does not. The two positrons annihilate with two electrons in the ionized core, and are converted to gamma rays. Charge is conserved in all of this, so that 4p+ and 4e- (neutral) are converted to 4He + 2e- (neutral). If not for the ionization it would be (net reaction) that 4 hydrogen atoms are converted to one helium plus gamma rays and two neutrinos. Forget the positrons. S B H arris 04:49, 14 September 2015 (UTC)
Muon catalyzed fusion is mentionned as a confinement method. This is strictly spoken not correct. Muon catalyzed fusion can occur always, irrespective of the confinement method. (I don't feel qualified to attempt to edit.) -- AvdH.
Someone wrote: It's odd & out of place to say for MCF and not the others. It implies that it might actually not be so in some eyes -- kind of like "perfectly legal" implies that something might actually NOT be legal! :
It was discussed some in the Cold fusion days, and so it was important to indicate that it worked. It might be long enough now that the distinction isn't needed. Seems to me that "perfectly legal" implies that some people might not know it is legal, not that it might not be legal. Gah4 ( talk) 03:01, 31 January 2017 (UTC)
A better way to teach this subject is from the stand point of Chemistry & the Periodic Table. The reason being that the system of filling electron orbital bears a direct relationship with the nucleus. Using the understanding of chemical bonding extends the creation of intermediate steps or bond formations, etc. Which extend into the nuclear aspect of the bonding orbitals (S, P, D & F)& how great role they play in nuclear chemistry. Basic electron in its orbital form implies the nucleus aspect that form is an required to be 'stable' element. —Preceding unsigned comment added by 72.184.40.168 ( talk) 08:48, 14 August 2009 (UTC)
I recommended to add more data on that table, such as the temperature in kelvin (K) relative to the electron volt (ev), and the data for Lithium 6 Deuterium (Li6D) reaction as well. —Preceding unsigned comment added by 203.59.13.178 ( talk) 01:24, 18 October 2009 (UTC)
This is an incorrect title. Years ago it had been speculated that the high temperature and pressure in sonoluminescence could lead to fusion. However, after serious studies of the temperatures were made, this possibility was discounted. The temperatures were demonstrated to be less than 30,000K. This is two orders of magnitude away from fusion temperatures at the estimated bubble pressures. (I have to read a 2008 ref that updates this work - http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=PLEEE8000078000003035301000001&idtype=cvips&gifs=yes ) Sonoluminescence probably should not be mentioned in the same context as sonofusion, because it causes a misinterpretation of the experiment and its intended results.
Sonofusion (the appropriate title for the paragraph), which is a similar technology as sonoluminescence, uses significantly different conditions (e.g., a cloud of bubbles, rather than the typical single bubble in sonoluminescence, and much greater pressure excursions) that greatly increase both the pressure and the temperature in the bubbles. Attempts have been made to show that according to conventional theory, both are adequate to explain the observed neutron production.
This paragraph is unnecessarily prejudicial (and POV). "As of 2005, experiments to determine whether fusion is occurring gave conflicting results." No references are given to support this. "As of 2005, some experiments were unable to reproduce Taleyarkhan's results" would be a more accurate and less prejudicial statement. An appropriate ref is C. G. Camara, S. D. Hopkins,* K. S. Suslick, and S. J. Putterman, “Upper Bound for Neutron Emission from Sonoluminescing Bubbles in Deuterated Acetone” PRL 98, 064301 (2007). The modified sentence should be followed by "More recently (2006), Taleyarkhan has confirmed his results in an experiment modified to counter criticism of his original technique. R. P. Taleyarkhan, C. D. West, R. T. Lahey, Jr., R. I. Nigmatulin, R. C. Block, and Y. Xu, “Nuclear Emissions During Self-Nucleated Acoustic Cavitation,” PRL 96, 034301 (2006)"
An additional sentence based on the 2007 reference should be included. "The most recent (2006) outside attempt to reproduce the Taleyarkhan results also failed. However, it was optimized for luminescence rather than for fusion products."
http://www.nature.com/news/2006/060109/full/060109-5.html is used as a reference for the original sentence "If fusion is occurring, it is because the local temperature and pressure are sufficiently high to produce hot fusion". It might not be considered a valid reference, since it appears to be an editorial, a tertiary reference that is not refereed. A better reference would be R. I. Nigmatulin, I. Sh. Akhatov, A. S. Topolnikov, R. Kh. Bolotnova, N. K. Vakhitova, R. T. Lahey, Jr., and R. P. Taleyarkhan, “Theory of supercompression of vapor bubbles and nanoscale thermonuclear fusion,” Phys. of Fluids 17, 107106 2005. Since the temperature and pressure is based on a theory, then the sentence should start with, "It is claimed that, if fusion is occurring..."
If the television results sentence is to be retained, then it needs a reference and, since it is not a scientific and refereed reference, it should be modified to indicate that the results were "suggested" rather than "shown."
The corrections suggested above are incorporated into the article. Aqm2241 ( talk) 20:38, 31 October 2009 (UTC)
Just a minor point. The article states "208 nucleons, corresponding to a diameter of about 6 nucleons" in the 4th paragraph of the requirements section. I may be completely on the wrong track here, but it seems to me that if a nucleus is roughly spherical (which I am pretty sure is true, and if not it's pointless to talk about its diameter) then you should be able to get an approximation of the total number of nucleons with 4π/3 * r^3.
If you have a diameter of 6 nucleons (thus r = 3), that gives roughly 38 nucleons total. Which seems to disagree with the article.
If you take the diameter as 7 nucleons (r = 3.5), then you end up with more like 180, which is significantly closer to 208
Might be splitting hairs, but it was just something I noticed.
BackStabbath ( talk) 01:14, 3 February 2010 (UTC)
If you furthermore want the ratio of diameters of a sphere packing process you have to increase the spherical volume size to accommodate the unfilled volume by about 35% and thus the spherical diameter by about 10% which in this case argues in favor of a 7 diameter multiple. But if you want to take into consideration the proposed volumetric independence of each sphere for spin compatibility purposes you also need to conceptualize a larger volume. Also, if you're willing to consider other accumulation configurations, such as cylindrical configurations as a means of accumulation consideration, you might consider the accumulation configurations shown in my nuclear model image in Talk:nuclear model. You might note that in his book "General Chemistry" Dr Linus Pauling showed images of spherical packing atomic models as "hypothetical models" with a degree of skepticism. WFPM ( talk) 18:14, 13 March 2010 (UTC)
"Only direct conversion of mass into energy, such as that caused by the collision of matter and antimatter, is more energetic per unit of mass than nuclear fusion."
Aren't blackholes also more efficient at converting mass into energy? Malamockq ( talk) 20:12, 23 April 2010 (UTC)
Yes. The collision recently observed by LIGO involved the conversion of roughly 5% of the initial black holes' mass to energy in the form of gravitational waves. Compare this to about 0.7% for fusion and 0.1% for fission. SamIAmNot ( talk) 22:45, 18 February 2016 (UTC)
What about electron-positron annihilation? The product is two massless photons. In DT fusion, the mass of the reaction products is lower than the mass of the reactants, and the missing mass is present in the kinetic energy of the reaction products. There may be a special relativity trick involving the centre-of-mass frame or something that I'm missing. 2001:630:12:10D0:2CB4:9415:E385:C14D ( talk) 15:24, 19 July 2013 (UTC)
In the article, the nuclear fusion with Helium-3 is nowhere described. Helium-3 is one of the best base materials to create a nuclear fusion; excavation of the material (actually lunar soil) is expected to begin on the moon in the (near ?) future (competitions for excavators are already done at Carnegie Mellon). A notable advantage is that no heat cycle needs to be run trough; ie the fusion creates instant electricity and does not need to be converted to heat, steam and only then to electricity. 91.182.139.158 ( talk) 18:12, 23 May 2010 (UTC)
In the article "Fusion reactions power the stars and produce all but the lightest elements in a process called nucleosynthesis." Shouldn't that read "heaviest"? jlodman 20:00, 7 June 2010 (UTC) —Preceding unsigned comment added by Jlodman ( talk • contribs)
I would say that in general when talking about powering the star that a supernova not be referenced as the star is destroyed, not powered, and add something that mentions supernovas in the context of an end-of-life exceptional case. "All but the lightest" was vague, and perhaps you could say "All but hydrogen-1" and add what you wrote here about the heavier elements. Just ideas. jlodman 17:18, 10 July 2010 (UTC)
From Nucleosynthesis#Stellar_nucleosynthesis the common reactions in stars don't produce Li, Be, or B. Even Z are produced by adding alpha, up to Fe or Ni. Higher odd Z through beta decay. Even higher, in supernovae. So, all except the lightest (Li, Be, B). Gah4 ( talk) 02:23, 27 November 2016 (UTC)
Is it? I would rather say "fission". Rursus dixit. ( mbork3!) 12:42, 18 June 2010 (UTC)
Fusion could take place at much lower temperatures due to Tunneling effect -- Hlfhjwlrdglsp ( talk) 20:51, 11 September 2010 (UTC)
There is an explanation of alpha decay which is pretty much alpha particles inside the nucleus moving at the fermi velocity and eventually tunneling out. The strong force acts over a short length, so the tunneling distance is pretty short for both alpha decay and fusion, but it is there. Gah4 ( talk) 01:54, 27 November 2016 (UTC)
Why "fussion" (with two "s") redirects here? I'm not a native speaker of english and wasn't sure of the correct spelling, tried with two "s" and was redirected to this page. But the spelling "fussion" doesn't appear even once in the entire article. It's a correct spelling? 188.86.65.35 ( talk) 12:57, 11 November 2010 (UTC)
After reading through the page on nuclear fusion, i was really impressed by the quality and detail shown and thus i recommend that the article receive a featured article stamp.
I don't. Too many mistakes. Also, the caption for the diagram on the left mahes no sense. — Preceding unsigned comment added by 184.147.123.113 ( talk) 22:04, 30 December 2012 (UTC)
The link to The FusionWiki has been reverted a couple of times, but seems legitimate and valuable. The Laboratorio Nacional de Fusión that hosts it has been around for decades, and the Wiki is a couple of years old. The list of articles is extensive, and many seem substantive, though technical. It is largely in English. Can we keep it unless there is consensus (and clear and specific evidence) that it is inappropriate? Thanks, Wwheaton ( talk) 17:18, 21 March 2011 (UTC)
I was the one putting the link. Some patrollers here think this is garbage and they can do it better. Ok, go ahead. The LNF hosting the site is the first impulsing the idea of having a wiki with specialist knowledge (it is not a personal effort). Scientists from over 10 countries have joined the effort up to now. They belong to laboratories such as Oak Ridge National Lab, Culham, Max Planck Institute for Plasma Physics or NIFS to name a few. It is fully in english although it is hosted in Spain. I have anonymously contributed to many articles in the WP but given the turn of events and present atmosphere I doubt I will ever do that again. Good luck to the few reasonable people that still remain here (for now). —Preceding unsigned comment added by 192.101.166.229 ( talk) 11:15, 23 March 2011 (UTC)
1. Several non-science people seem confused by the explanation at the beginning of this article, as illustrated by the picture included of D+He3. The term was coined to describe the macroscopic astrological phenomenon of the stepwise H+H+H+H=He or miraculous 4H=He. Reactions like 2H + 6Li = 2 4He or 1H + 11B = 3 4He (in Aneutronic fusion) to the layman appear to be Fission reactions.
2. The reference to Quantum tunneling should reference Muon-catalyzed fusion or include references of its own. One concept in tunneling that is not realistically described in this article (and would be apparent if contributors read references) is that tunneling probability has a time variable. This is truly catalysis because the Muons induce several hundred fusions before being expended (decay). The contact time as described by the thermal temperature, hence the speed of even low temp particles, in Plasma is around 6 orders of magnitude shorter than Muon induction. This makes it extremely unlikely that "quantum tunneling" is responsible for the low energy plasma reactions. As Deuterium Molecules greatly outnumber Helium atoms produced it would be unlikely for Muon to find one; and the 4-14 MeV (product 3H or 3He or 4He) energy of reaction effectively separates the Muon for the next reaction. See http://www.iaea.org/inis/collection/NCLCollectionStore/_Public/25/048/25048388.pdf. Shjacks45 ( talk) 05:33, 7 August 2011 (UTC)
The models described are from particle beam reactions in accelerators. Or low density high temperature plasma experiments. Under Neutron source ( Neutron generator) the fusion reactions that generate neutrons are from nuclei accelerated to as little as 5,000 volts.
Solar fusion conditions are quite different. The condensed matter (tons per CC) inside the Sun has a internuclear distance and short free path that favors tunneling. As atoms have been broken down the electrons in Solar plasma are closer than atomic orbital electrons. Although endothermic in 10E7 temperature environment, electron capture by a proton to form a neutron, or electron capture by the two proton 2He seems feasible. Gammas at solar temperatures can spontaneously form electron-positron pairs. Need to consider Deuterium "decay" due to solar thermal environment exceeds binding energy. Helium burning is discounted however Tritium and 3He "burn" at Hydrogen fusion temps. (Biggest problem of fusion is excess energy causes fission of products; intra-Solar conditions favors endothermic reactions e.g. proton-proton fusion with emission of positron to remove excess energy?)
The Deuterium reactions show a drop off above 1.5 MeV; Deuterium binding energy is 2.2 MeV, splitting of Deuterium by Gammas is used in Neutron sources. Tritium fissions at lower energy. Shjacks45 ( talk) 05:23, 26 August 2011 (UTC)
From sun, the average density if 1.4 g cm-3. That is, less than the earth. Gah4 ( talk) 03:13, 3 June 2018 (UTC)
The "citation needed" information is found under
Tritium.
Re: "This is due to a greater disintegration rate for 62Ni in the interior of stars driven by photon absorption." Any chance that Proton absorption is the real culprit? Ϣere SpielChequers 18:55, 31 August 2011 (UTC)
Text and/or other creative content from this version of Nuclear fusion was copied or moved into Thermonuclear fusion with this edit. The former page's history now serves to provide attribution for that content in the latter page, and it must not be deleted as long as the latter page exists. |
How did they compute the product energies for reaction 6iii? Since it's a 3-body problem, there's 2 equations with 3 unknowns. — Preceding unsigned comment added by Promptjump ( talk • contribs) 16:24, 18 July 2012 (UTC)
As of Sept 25, 2012 NIF is certain to miss its Sept 30 deadline to achieve break-even. By law the facility has 60 days to prepare a report on the remaining barriers and way forward. The likely outcome (Science 9/21/2012 pg 1444) is that confinement by indirect laser inertial confinement will be abandoned as an approach to fusion energy. The NIF will continue to be used to model fusion in support of the US nuclear weapons stockpile. To date model calculations have failed to predict the observed physics. — Preceding unsigned comment added by 216.96.79.86 ( talk) 17:50, 28 September 2012 (UTC)
Is anyone even paying attention? Break-even for energy inputted by lasers was reached at NIF. It's not ignition, but it's a huge step. Netdragon ( talk) 04:08, 15 October 2013 (UTC) See below:
Ignition experiments continue on the NIF and is it not likely that indirect-drive fusion will be abandoned.
https://www.llnl.gov/news/newsreleases/2013/Feb/NR-13-02-07.html
https://lasers.llnl.gov/newsroom/project_status/index.php
-- 129.31.243.172 ( talk) 14:11, 10 June 2013 (UTC)
Reactions 6i and 6iii have the same input and the same reaction products, but produce different amounts of energy. How is that possible?
(6i) 3He + T → 4He + p+ + n0 + 12.1 MeV (6iii) 3He + T → 4He (0.5 MeV) + n0 (1.9 MeV) + p+ (11.9 MeV) [totalling up to 14.3 MeV]
Geoffrey.landis ( talk) 16:29, 3 December 2012 (UTC)
I have just been lookng at the Encyclopaedic Dictionary of Astrophysics, by S.K. Basu on Google Books. It appears that much of this Wikipedia article is a straight plagiarism/copy-and-paste from this book.
For example, if you read from "Important Reactions" on page 264 of Basu's book, you will see that it is word-for-word identical to the "Important Reactions" section on this Wikipedia page.
Could somebody please inform me what the Wikipedia policy on this is? The entire text is not available on Google Books so I am assuming that the work is still in copyright and that the plagiarism on this site may well be illegal. — Preceding unsigned comment added by 92.237.144.193 ( talk) 18:45, 24 December 2012 (UTC)
= furthermore the section on fuel cycles contains much text lifted from Basu's book.
This needs the cross sections for more reactions. This includes those listed, but also other reactions. Does anyone know the details around the reactions that generate helium? — Preceding unsigned comment added by 69.205.70.3 ( talk) 00:11, 17 January 2014 (UTC)
Looks like that researchers managed to generated more energy than put into it using a beam-target fusion. [1] -- PLNR ( talk) 13:39, 13 February 2014 (UTC)
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I'm thinking here about the bonding between positive nuclei. Obviously protons/nuclei overcome the electrostatic force and come into proximity, at which point fusion may occur due to the strong interaction. But exactly how this happens is represented differently in some lay sources, and I'd like to check we get it right.
Some sources represent this process of being able to overcome electromagnetic forces as being mediated by random quantum tunneling. Other sources state it's an effect of sufficient kinetic energy. While fusion itself is primarily an effect of the strong interaction, it's not entirely clear whether some fusion processes also involve effects due to the weak interaction as well (eg if a non-nucleon particle is ejected during the fusion such as an electron/positron/neutrino).
Are we being sufficiently clear (especially in the introduction which is simpler text) which interactions/effects permit fusion / are involved in it? FT2 ( Talk | email) 06:31, 5 September 2017 (UTC)
I just wanted to thank the authors of the section on which fusion reactions are plausible candidates for a source of sustainable fusion power. That's the question that interests me, and your answer is clear, well-organized, precise, and comprehensive. Keep up the good work! Invisible Flying Mangoes ( talk) 02:35, 12 September 2017 (UTC)
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The graph at upper right is mislabeled and incorrectly described. It is not a graph of binding energy; in reality, binding energy continues to increase going to the right of Fe-56 as the number of nucleons increases. The correct y axis label "Average Binding Energy per Nucleon", is an important distinction. Recommend using the terms and description used for the same graph located in the Wikipedia article entitled "Iron Peak".
The graph helps to explain, using a single curve, how fission and fusion are possible. The y maximum at Fe-56 implies that Fe-56, with a relatively high average binding energy per nucleon, is held together tighter than nuclides on either side of Fe-56, where the average binding energy per nucleon decreases in either direction. Energy is released, both when lighter nuclides fuse to form something heavier, and when heavier nuclides fission to form lighter ones. In addition, energy must be added to initiate the reaction in either case, except when certain heavy nuclides fission spontaneously.
The current description in this article is nonsense: "The formation of nuclei with masses up to Iron-56 releases energy, while forming those that are heavier requires energy input. This is because the nuclei below Iron-56 have high binding energies, while the heavier ones have lower binding energies." No. That is not what this graph is saying at all. Jthomason3 ( talk) 02:15, 3 June 2018 (UTC)
In the first paragraph of the lede, it is said, as a blanket statement: "The difference in mass between the reactants and products is manifested as the release of large amounts of energy." Then, in the second paragraph, it is said: "A fusion process that produces a nucleus lighter than iron-56 or nickel-62 will generally yield a net energy release. These elements have the smallest mass per nucleon and the largest binding energy per nucleon, respectively. Fusion of light elements toward these releases energy (an exothermic process), while a fusion producing nuclei heavier than these elements will result in energy retained by the resulting nucleons, and the resulting reaction is endothermic." So, in my interpretation, fusion of very heavy elements do not result in a release of energy, contradicting the blanket statement made in the first paragraph. I will fix this, unless somebody tells me that I'm not understanding something. Attic Salt ( talk)
Okay, I went ahead and fixed the sentence in the first paragraph of the lede. Attic Salt ( talk) 21:49, 4 September 2018 (UTC)
References
an old idea which was mechanically impossible...
Pressure waves by trembling shields which focus on a central ring of the fusion torus have been suggested. The shields should not touch somewhere, but should be held in place magnetically. It is extremely hard not to break the shileds while they tremble hard enough. A spherical (non-toroid) chamber with two poles (looping input and output for the gasses) has been proposed. A spherical chamber will have a more concentrated pressure center.
Is it appropriate to mention Greenhouse Item in the opening?
It seems to me we should be discussing self-sustaining fusion there, and Greenhouse Item wasn't. It was the fusion of a few grams of D-T driven by several kilograms of fissile material, not self-sustaining fusion. Boosting isn't used to provide extra energy to a nuclear weapon, it's used to provide additional neutrons. I'm not sure it's appropriate to include it. Staged thermonuclear weapons? Sure, mention it because the secondary stages clearly output more energy than goes into them, but I'm not so sure about boosted weapons. Kylesenior ( talk) 07:15, 28 May 2020 (UTC)
Why is the mention of the neutrinos produced almost entirely missing (except in the CNO cycle section) and neutrinos are missing from all reaction equations? -- vuo ( talk) 11:32, 3 August 2020 (UTC)
This article seems to be duplicated by thermonuclear fusion, which should I think be merged into this one.
They seem to be exactly the same topic, and this article name is the more concise.
Discuss here I think. I have placed a heads-up at Talk:Thermonuclear fusion#Possible merge and redirect. Andrewa ( talk) 13:37, 1 May 2021 (UTC)
Merge. "Thermonuclear fusion" is the one driven by high temperature, so it has a bit narrower scope. However, only the Nuclear fusion's subsections Beam…, Muon…, and Other principles fall outside of that scope, so it does not make sense to duplicate all the rest. Petr Matas 18:26, 18 June 2022 (UTC)
This infamous falacy is at work in the following 2 sentences:
"At the temperatures and densities in stellar cores, the rates of fusion reactions are notoriously slow. For example, at solar core temperature (T ≈ 15 MK) and density (160 g/cm3), the energy release rate is only 276 μW/cm3—about a quarter of the volumetric rate at which a resting human body generates heat."
The number 276 μW/cm^3 results from dividing the total solar power output (~4*10^26 W) by the total volume of the sun (~4/3π*696,000,000 m^3) and is fairly irrelevant, yet fun to know. But in this case the message is really quite wrong because a point is made regarding the energy release rate at core-temperature (15 MK) and -density (150 t/m^3). So the total energy certainly needs to be divided by the volume in which fusion occurs at all, i.e. the core. Taking the number of 24% of the solar radius, found with a quick search on Wikipedia itself, one arrives at in SI units) which is about 70x the number currently stated. Can I correct this number? This is obviously original research and I don't have a source for it, but since it is so simple to verify, is a source really necessary? -- Felix Tritschler ( talk) 12:37, 8 March 2022 (UTC)
Unit is given, in the diagram, as m³/s for the reaction rate. This does not add up. number density is mol/m³, σ (cross section, area) is m² and v is velocity is m/s. In total we get: mol/m³ * mol/m³ * m² * m/s = mol²/(m³*s). We have mol² left over to get to m³/s, missing somewhere, potentially in the cross section?
But it does not end here, this paper [2] states:
Per time per volume, that would be 1/(s*m³) for the reaction rate. Not m³/s as per wiki. It makes more sense this way, since we want to multiply this by some reactive plasma volume and some amount of time to get the conversion. The formula given is (ignoring the integers, since they have no units):
As we already established, that adds up to mol²/(m³*s), with factors on the right missing the mole(s) (or they need to be included on the left).
1. We have some missing units
2. Reaction rate has a different unit, either mol²/(m³*s) or 1/(m³*s), but not m³/s
I come from the chemical side of things, I am not going to edit this without feedback on how Physicists handle units and what they think is missing.
Eheran (
talk) 13:17, 17 May 2023 (UTC)