Talk:Nuclear fusion

Needs Section on Development for Commercial Use

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)

But where does the energy come from?

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)

Matter can be organized in different ways. Some of those ways are more stable than others. Unstable states are unstable because they have a lot of potential energy. If you take some matter and reorganize it into a more stable state, that potential energy is released. In fusion, deuterium (hydrogen-2) and tritium (hydrogen-3) are not as stable as helium and a neutron, so the reaction D + T -> He + n releases energy (the products come out of the reaction moving much faster than the reactants went in). We capture that energy as heat and use it to generate electricity. Canonymous 18:04, 15 September 2006 (UTC)

Isn't the plain English explanation just that a small part of the reactant mass ceases to exist as matter? It's converted into energy. It's a small portion, to be sure, as opposed to antimatter, where 100% of reactants are converted into some form of energy or neutrinos, with no quarks left to tell the tale. Sacxpert 10:48, 17 November 2006 (UTC)

This does happen, but isn't the reason. Consider someone asking how a flashlight battery works. As with all cases, as the stored energy decreases, the mass decreases, but that doesn't explain the chemical reactions that cause the mass change. In both the battery and fusion reaction, the products have a lower (free) energy, making energy available for our use. Gah4 (talk) 09:04, 5 September 2017 (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)

Fission products have lower potential (nuclear) energy than the input U235. They normally have more neutrons than the more stable nuclide with that number of nucleons. Some neutrons are released in fission, but not enough for the products to be most stable. Gah4 (talk) 09:04, 5 September 2017 (UTC)

The absorption of a neutron places some nuclei into an "invalid" quantum state; the nucleus reacts to this illegal rearrangement by "vibrating" itself into valid smaller nuclei, after throwing away various items, including x-ray photons and more neutrons. Which nuclei? Big ones, where the outer nucleons are "far" from the center of the nucleus, and at these vast distances, the outermost nucleons feel a weaker nuclear force- recall, the nuclear force works only at short distances. -Dawn McGatney 69.139.231.9 (talk) 13:04, 1 April 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)

A large part of the "mass" of a proton already "is" energy from the beginning: The sum of the masses of the three quarks of which the proton consists only make up about 10% of the total mass of a proton, the rest is "field energy" from the strong force's field. So you have a large pool of energy to draw from in fusions. It's similar to an asteroid falling on Earth, which also produces lots of energy without destroying any particles from either the asteroid or the Earth: there the energy comes from the loss of gravitational energy of the asteroid in Earth's gravitational field. Hope this helps.--Roentgenium111 (talk) 16:25, 22 April 2009 (UTC)

Similar to the stability of noble gases, with their full electron shells, the alpha particle (He4 nucleus) has full nuclear shells. The binding is especially strong for alpha. There can be two (opposite spin) protons in the first proton shell, and two neutrons in the first neutron shell. The best model for alpha decay of heavy nuclei is that alpha particles are moving around at high speed (the Fermi velocity) inside, and eventually tunnel out. They tunnel as a bound state, similar to Cooper pairs in superconductors tunneling through a Josephson junction. Gah4 (talk) 09:04, 5 September 2017 (UTC)

BTW: I suppose you mean "fission" in your 2nd sentence? --Roentgenium111 (talk) 16:25, 22 April 2009 (UTC)

The title is a sentence (or something like one). Nuclear fusion. Midgley (talk) 16:54, 22 April 2009 (UTC)

For quantum mechanical reason, the alpha particle (Helium nucleus) is especially stable, for similar reasons to the chemical stability (inertness) of Helium. Two protons (with opposite spin) and two neutrons (also with opposite spin) pack very tightly, minimizing the quantum exchange energy. They are so tightly bound, that larger nuclei can be considered as having alpha particles moving around (at the fermi velocity), and alpha decay occurs when one tunnels out of the nucleus. Fundamentally, it is the result of the quantum mechanical exchange interaction (sometimes called exchange force). There is no classical analog, and no easy way to explain it. It is related to indistinguishability, which also has no classical analog. Gah4 (talk) 23:35, 15 March 2019 (UTC)

Image

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:

1. It takes 23 seconds to watch the whole animation to figure out what happens. A diagram can be understood basically instantly. (Consider that there are even ways to do this better by means of animation. This page has a DT reaction that basically takes 4 seconds and is just as easy to understand.)
2. The animation does nothing other than showing two things coming together and a third thing coming out of it. Again, a diagram can do this much more efficiently.
3. The animation portrays the "energy" released as a circular yellow beam. This is misleading. Most of the energy out of that particular reaction is in the kinetic force of the neutron that is being released and the kinetic force of the alpha particle. This makes it look like the "energy" is some sort of separate thing from the byproducts of the reaction, which it is not. In any case it leaves out a lot of the energy. The neutron goes off with 14.1 MeV, while the alpha particle, rather than staying still in the center, flies off with a kinetic energy of 3.5 MeV.

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)

break-even, boosterism

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)

Yep. Controlled fusion for commercial power production has been "just 20 years away" for the last 50 years. I'm beginning to wonder if it won't be just 20 years away for the next 50 years, too. ;). SBHarris 01:59, 5 April 2009 (UTC)

It is the energy of the future! Meaning it will always be a future date when we will learn to harness it.72.12.199.20 (talk) 01:34, 17 December 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)

I haven't followed this for a while, but there are different definitions of breakeven. One counts only the energy in the fusion reactor, but the energy needed to confine the reaction. (That is, the magnets for Tokamaks.) If you use superconducting magnets (low electrical power input, but there is need for coolant). There is also energy needed to make Tritium, which needs to be considered for a production power plant. Gah4 (talk) 09:11, 5 September 2017 (UTC)

There is Fusion_energy_gain_factor which has a good explanation for the different levels of breakeven, such as scientific, engineering, and economic. I suspect it is better there, and to link from here. Gah4 (talk) 03:22, 25 June 2020 (UTC)

possible fusion shortcut

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)

editing required

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)

There is no need to do that, because the emission of the positrons and neutrinos is exactly simultaneous, and certainly it is not one emission over the other than accomplishes the conversion of up-quark to a down-quark. Technically, it is the emission of a virtual W+ boson that changes proton to neutron. Then the W+ boson decays into a positron and electron neutrino.

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. SBHarris 04:49, 14 September 2015 (UTC)

Thank you. Richard B. Woods (talk) 05:28, 14 September 2015 (UTC)

muon catalyzed fusion

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.

Well, it does get specific nuclei together, so small scale confinement. Gah4 (talk) 03:01, 31 January 2017 (UTC)

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)

Trail Offer: Chemistry & the Periodic Table.

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)

More Data at Table: Temperature, Lithium 6 Deuterium ?

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)

After reading Richard Rhodes' book "The making of the Atomic Bomb" We can say that "we have done that". And in Kaplan,s "Nuclear Physics" book tells us that we did lithium7 plus proton fusion prior to 1933. But we seem to be stuck on fast neutron generation technology.WFPM (talk) 18:48, 13 March 2010 (UTC)

Sonoluminescence

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)

I think the claims of R. P Taleyarkhan re sonofusion remain highly controversial and probably do not yet deserve explicit mention in this article, except perhaps for a link to a separate article on the sonofusion controversy. Taleyarkan has been accused of research misconduct at Purdue here ("Panel finds misconduct by bubble fusion researcher" New Scientist, July 2008), and while I am not clear that the case is finally settled, I believe there has been no generally accepted or independent confirmation of his claims as of October 2009. I am going to revert Aqm2241 (talk)'s edits on this pending further discussion and consensus here, though I am not an expert on the subject. It will not hurt Wikipdia to have this (POV, in my opinion) material withheld for a few days or weeks until we reach consensus here. Apologies to any injured toes meanwhile. Wwheaton (talk) 00:40, 1 November 2009 (UTC)

Wwheaton has provided a reasonable and gentlemanly response. Nevertheless, he has fallen into the same trap that so many experience. He has been diverted from many scientific results and theoretical papers (by over 10 reputable authors), in high-quality refereed journals by the false accusations of "interested" parties. The false claims/accusations (none have ever been confirmed) will never cost the obstructionists anything. However, by their bogus technical "challenges" to the experimental results and by inciting political witch hunts against the lead author, they have made the work "controversial" and have put back sonofusion research (and diverted/blocked funding) for probably 5 years.

Whether or not there is any "independent" claims in print of the physical effect, the theoretical papers on the subject (some of which do not have Taleyarkhan's name attached) should provide a sufficient basis for mentioning that there may be an option for attaining sufficiently high temperatures and pressures for nuclear fusion without resorting to the normal hot fusion approach. Since these independent papers reference Taleyarkhan's papers, he cannot be completely excluded if they are referenced. Therefore, it would make more sense to refer to the original papers in this article, particularly since the results were repeatedly and publically demonstrated. "Successful public demonstration on March 1, 2006. This was the all-day demonstration of bubble fusion in full view of the following visitors: Bill Coblenz from DARPA; Graham Hubler and Peter Schmidt from the Office of Naval Research; Ross Tessien, Felipe Gaitan and Wylene Dunbar from Impulse Devices Inc.; Ken Suslick and another one or two people from the University of Illinois; Seth Putterman and perhaps one more person from UCLA; JaeSeon Cho from Oak Ridge, plus about five to ten Purdue students and staff. Neutron production data were obtained and viewed by the various visitors that afternoon commensurate with the data published ...in Physical Review Letters ... Jan.2006."

For a full accounting of the diversion from the physics, one can go to a major study and record of the controversy at New Energy Times. In particular, to put the New Scientist ref in perspective one might look at http://www.newenergytimes.com/v2/bubblegate/2008/2008SonofusionResearchScuttled.pdf. (Go to bottom of p 12 & top of 13). If we allow a "hatchet job" to block mention of published work, then we will have allowed this travesty to continue and further reward the perpetrators.Aqm2241 (talk) 18:49, 1 November 2009 (UTC)

Thanks, I do appreciate that scientific consensus is sometimes a weirdly dicey thing, given the powerful interests of special parties, and the practical inability of everyone to be knowledgeable about everything. It amazes me that the enormous value to (practically all of) us of truly controlled and low cost fusion energy does not sweep all personal and institutional considerations aside, but such is Homo Sapiens. Wikipedia policy actually gives higher ranking to third party sources such as review articles and news reports in academic journals than to primary sources themselves, even when ostensibly peer-reviewed, as that also is sometimes not as reliable as one could wish. I came to this reversion vaguely remembering a very recent (surely < 1 month old) news article in Science or Nature re the Purdue case, which (if I can trust my memory at all) asserted that (a) the misconduct issue was not finally settled, and (b) sonofusion has not been generally accepted as a real phenomenon by the community of experts. (Unfortunately after briefly searching all my remaining copies of those two journals, and looking at the journals' web sites, I have failed to find that late reference.) But since Taleyarkan's early work (first published in Science) dates from 2002, and this latest 2009 article is more recent than any of the references given here, I must accept that sonofusion remains on the fringe for the time being. I have looked at your "New Energy Times" reference and some of the links from it, and do not find it convincing; perhaps other editors will disagree. I recommend that our article here simply mention that the controversy remains unsettled after several years, with a link to bubble fusion or sonofusion, where the issues can be presented in more detail. It is important that this main-line article on nuclear fusion not become unbalanced by theories not yet part of the community consensus. This case seems similar to cold fusion, though that is perhaps more settled (negatively, I think). Best, Wwheaton (talk) 22:02, 1 November 2009 (UTC)

I concur with your recommendation "...that our article here simply mention that the controversy remains unsettled after several years, with a link to bubble fusion or sonofusion." Therefore, I suggest inserting "Sonofusion or bubble fusion, a controversial variation on the sonoluminescence theme, suggests that acoustic shock waves, creating temporary bubbles (cavitation) that expand and collapse shortly after creation, can produce temperatures and pressures sufficient for nuclear fusion [9]." in place of the present paragraph.

Any comments against SF would need to be balanced by pro-SF comments to maintain Wiki neutrality in the controversy. Referring to the Bubble Fusion topic is an appropriate stand and nothing more need to be said. Since the BBC citation is in the BF topic, this sentence is not needed here.

With this consensus, the suggested substitution (or a variant) can be utilized to close this talk session. Aqm2241 (talk) 05:21, 2 November 2009 (UTC)

RE ClueBot's revert: I thought that I had seen another ref 9. I was not sure how Wiki handled it. I now remember other examples of duplicate citations to the same ref. and should have checked them out before I submitted a non-standard version of a citation.Aqm2241 (talk) 02:59, 4 November 2009 (UTC)

Nuclear diameter

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 want the ratio of the radii (or diameters) of two spheres, one of which is 208 times the volume of other, the ratio is 208^(1/3) = 5.92. The sphere with 208 times the volume will have almost 6 times the linear dimensions of the other. The constants in front drop out of these ratios. That factor is what you're adding, but shouldn't. SBHarris 01:56, 3 February 2010 (UT

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)

No. It is usual to picture a nucleus as a ball of protons and neutrons packed together. Note that Pauli exclusion applies to protons and neutrons separately, such that two (opposite spin) protons and two (opposite spin) neutrons can pack as one. They are still quantum objects, and so somewhat fuzzy, but not as fuzzy as electrons in atomic shells. The actual requirement is to fill up shells satisfying Pauli exclusion, with additional nucleons having higher and higher Fermi energy, and so Fermi momentum, which, with Heisenberg uncertainty, determines the size. Consider also the sizes of atoms as atomic number increases. Gah4 (talk) 09:28, 5 September 2017 (UTC)

It is common to describe nuclei, not by diameter but by area, called cross section. If you shoot a neutron, for example, at a nucleus, the cross section is the area that describes the chance of hitting (interacting) with the nucleus, as it might for a neutron to go through a hole with that area. Because of the large de Broglie wavelength for slow neutrons, use the fast neutron cross section. The unit barn is commonly used for nuclei cross section. Gah4 (talk) 00:28, 16 March 2019 (UTC)

Efficiency?

"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)

Conversion of mass into energy is an erroneous phrasing/misconception/confusion, the mass does not convert into energy.--79.116.78.65 (talk) 20:10, 11 September 2010 (UTC)

That is correct. Matter can be converted to energy. Which is to say: particles considered matter can be converted to particles not considered matter (as when electrons and positrons are coverted to photons). But in this process, mass is conservered. Both matter and energy retain their mass, which cannot be created nor destroyed. SBHarris 01:26, 16 October 2010 (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)

Yes this is a relativity problem, and there are different ways to explain it. Potential energy has mass (that which you can measure on scales and balances) but not rest mass. One way to see it, is to slow down all reaction products (converting their kinetic energy to heat) and then measure the rest mass of the products. It is now usual in relativity to call what used to be rest mass as just mass. Energy (kinetic or potential) is not mass, even though scales and balances will measure it. Gah4 (talk) 09:48, 5 September 2017 (UTC)

Helium-3

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)

I'm not sure I understand your comment correctly. How would ³He generate electricity directly? As far as I know, any fusion reactor would use the heat generated to drive a turbine. Also, if you're referring to a D-³He fusion reaction, this is far more complicated to do than (the currently favored) D-T reaction, since the fusion cross section is roughly 4 orders of magnitude lower. —Preceding unsigned comment added by 128.151.32.169 (talk) 23:40, 5 February 2011 (UTC)

Aneutronic fusion, like Helium-3 fusion, generaly gives most of it's energy in the form of high speed charged particles, like protons or alpha particles. You can theorically generate direct eletric current decelerating those particles, with an much higher efficiency than heat cycle. See polywell and focus fusion that hope to generate power that way.

Now, there already is some fair mention to Helium-3 fusion, but I still would like the detailed tables to include ³He-³He fusion in addition to D-³He. It would be the favoured fusion for an Lunar or Juvenian base, if we can make it work. Caroliano (talk) 18:47, 25 June 2011 (UTC)

Error in Article?

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)

Hmm, neither. Stellar nucleosynthesis generally produces all elements up to lead, not the heaviest uranium and thorium, but also generally not the lightest hydrogen-1. However in exceptional cases, similar to supernovae, every element is produced without exception, including hydrogen-1 (photodissociation), lead, thorium, uranium up to californium through the r-process. As a provisional formulation, I'll just remove "but the lightest". Rursus dixit. (^mbork³!) 12:42, 18 June 2010 (UTC)

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)

Well, but then why the senctence: "The extreme astrophysical event of a supernova can produce enough energy to fuse nuclei into elements heavier than iron."?

Edit: E.g. in the Wiki article on neutron capture, it says:"Nuclei of masses greater than 56 cannot be formed by thermonuclear reactions (i.e. by nuclear fusion), but can be formed by neutron capture."

In general, these processes are not called "fusion". They are rather addressed as "nucleosynthesis" (which, of course, also entails nuclear fusion).

--> The sentence:"Fusion powers stars and produces virtually all elements in a process called nucleosynthesis." at least is confusing - semantically, it is wrong because it means: fusion = nucleosynthesis (and vice versa).

--Felix Tritschler (talk) 19:46, 1 March 2019 (UTC)

¹p + ¹¹B → 3·⁴He is fusion?

Is it? I would rather say "fission". Rursus dixit. (^mbork³!) 12:42, 18 June 2010 (UTC)

Its fusion. It starts with 11 fused baryons and ends with 12 fused baryons plus the release of energy. --LiamE (talk) 13:04, 18 June 2010 (UTC)

OK, I see, thanks for answering! I've heard it being called "fusion", but I just wanted to be sure. Rursus dixit. (^mbork³!) 15:51, 20 June 2010 (UTC)

BTW, the mass numbers:

3 · 4.002604 = 12.007812 for 3 · ⁴He, and

1.007825+11.009305 = 12.01713 for ¹p + ¹¹B.

I think the number of "fused baryons" is irrelevant, since it might occur in what's normally regarded as nuclear fission. Rursus dixit. (^mbork³!) 07:46, 21 June 2010 (UTC)

Yeah you are right. The number of fused baryons doesnt technically matter. Having had a good think about I'm still convinced its a fusion reaction overall though as the primary realease of energy is due to fusion not fission, although a fission did indeed take place. If we look at a fission we might have P (or N or Alpha) + large nucleus fusing, then fissioning to release energy (where inded all the baryons could still be fused hence my rethink). We would still call that fission though a fusion took place. Incidentally I think we will hear a great deal more about the P + B11 reaction in future as it is a fusion reaction with a large cross section and with very low neutron production, thus making it a candidate for a workable fusion reactor, thought the temperatures needed to kick it off are very high. Having a look through papers scientists universally refer to it as a fusion reaction and they do tend to be right about these things though I cant give you a watertight explanation as to why. I'm sure some nuclear physicist will clear it up for us sooner or later. --LiamE (talk) 13:09, 25 June 2010 (UTC)

You could also call it an (n,2alpha) reaction. The distinction is not clear cut. Like LiamE said, "scientists universally refer to it as a fusion reaction", so we do too. --Art Carlson (talk) 15:03, 25 June 2010 (UTC)

Still been mulling this over. While the "scientists universally refer to it as a fusion reaction" explanation of why we call it fusion here (verifiablity) it doesnt answer why they call it a fusion. It occured to me that alpha and beta decay are never refered to as a fission though in a small particle such as B11 alpha decay is effectively a fission of sorts. So what we have here is fusion and alpha decay rather than fusion and fission. I also suspect that unlike in fission reactions where the inherent instability of the nuclide causes the fisson here the fusion releases the energy that forces the decay to take place. --LiamE (talk) 06:04, 6 July 2010 (UTC)

Fission is specifically a decay method for large nuclei based on the liquid drop model. Small nuclei decaying into other small products is not fission. In many cases, small nuclei decay in what is pretty much alpha decay. Gah4 (talk) 02:07, 27 November 2016 (UTC)

Wouldn't the "fusion" part of the reaction be where the accumulation part resulted in the creation of the composite nucleus EE6C12, with an AMU mass value of 12.000000? Then the subsequent breakup of the 6C12 nucleus would be a conditional fission process depending on circumstances? Also, how about achieving the fusion of a 6C12 nucleus by the fusion of a 1D2 nucleus(2.014101778) with a 5B10 nucleus (10.0129370), total (12.02705478)? How unfavorable is this relative to the proposed 1P1 + 5Be11 proposed fusion process?WFPM (talk) 18:22, 31 July 2010 (UTC)

It is further to be noted that the bombardment of both 5Be10 and 5Be11 with 1D2 nuclei would have the effect of increasing the composite nuclei of the target nuclei to their stable level of EE6C12 and EO6C13.WFPM (talk) 18:56, 31 July 2010 (UTC)

Also note that you are looking at statistical distribution. Sometimes the product is C12 plus gamma, sometimes it is He4 plus Be8 which then decays to 2 He4. Neutron plus Li7 gives Li8 which then decays (.01 sec) to Be8 then to 2 He4. Fast Neutron plus Li7 gives Li6 plus 2 neutrons. Yet U235 + N gives U236* a high energy metastable state of stable U236. Hydrogen bomb describes that fission may also occur by high energy gamma absorption, bringing the atom to its unstable spontaneous fission state. N + Li6 > Li7* > He4 + H3 but gamma + Li7 > Li7* also. Shjacks45 (talk) 05:49, 7 August 2011 (UTC)

Fission is related to the liquid drop model, and the balance of electrostatic and nuclear forces. That occurs in heavier nuclei. Fusion is mostly related to the especially stable alpha particle (He4 nucleus), and so is the reason the B11 reaction is a fusion reaction. Gah4 (talk) 22:25, 1 March 2019 (UTC)

Tunneling effect

Fusion could take place at much lower temperatures due to Tunneling effect --Hlfhjwlrdglsp (talk) 20:51, 11 September 2010 (UTC)

Compared to what? —Keenan Pepper 00:36, 12 September 2010 (UTC)

To what is considered in current models on nuclear fusion.--79.116.77.56 (talk) 20:55, 15 October 2010 (UTC)

Current models include the effect of tunneling. Moreover, they are backstopped by actual measurements of rates, so the calculations are proven corrent.SBHarris 01:22, 16 October 2010 (UTC)

What is the actual nuclear-nuclear distance for the condensed matter inside the Sun? I've never seen any "Current Models" take that into account for tunneling contribution; every model I've seen is based on free space interaction of nuclei that have been studied in beam accelerators. I really doubt that there is any significant mean free path inside Stars. Shjacks45 (talk) 17:56, 25 August 2011 (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" redirects here?

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)

Incorrect spelling, a common mistake. Binksternet (talk) 14:41, 11 November 2010 (UTC)

Indeed, fusion is the correst spelling. It doesn't help that u and i are next to each other on most if not all keyboards, and the opposite process to nuclear fusion is nuclear fission. 62.252.178.158 (talk) 12:23, 20 February 2011 (UTC)

There's a Mackie loudspeaker product line called Fussion, but it does not merit an article—not so notable on its own. The redirect is properly aimed here. Binksternet (talk) 15:58, 20 February 2011 (UTC)

Quality

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)

Laboratorio Nacional de Fusión FusionWiki link

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)

Con-fusion

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)

As I recently noted above: Fission is related to the liquid drop model, and the balance of electrostatic and nuclear forces. That occurs in heavier nuclei. Fusion is mostly related to the especially stable alpha particle (He4 nucleus), and so is the reason the B11 reaction is a fusion reaction. Gah4 (talk) 22:34, 1 March 2019 (UTC)

Unrealistic Fusion Model

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.

photon absorption

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? ϢereSpielChequers 18:55, 31 August 2011 (UTC)

³He-T fusion

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)

The reaction proceeds in two (very fast) steps:

3 2He

+

3 1T

→

5 2He

(

2.4 MeV

)

+

p+

(

11.9 MeV

)

5 2He

→

4 2He

(

0.5 MeV

)

+

n0

(

1.9 MeV

)

That's not exactly right because the decay of the He-5 contributes some energy, and the energy of the He-4 and n will be spread out depending on which direction they decay relative to the original direction of the He-5, but it's close. Art Carlson (talk) 19:59, 18 July 2012 (UTC)

As far as I know, a reaction like this is written in the center of mass frame. You have to add yourself any kinetic energy of the source nucleus. Since if could be along a different axis from the second decay, you can't easily add the energies, but you do know the total. Gah4 (talk) 01:35, 27 November 2016 (UTC)

National Ignition Facility

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:

• http://www.cbsnews.com/8301-205_162-57606588/apparent-breakthrough-in-nuclear-fusion-silenced-by-shutdown/
• http://www.nbcnews.com/science/fusion-milestone-reached-shutdown-stymies-further-progress-8C11381186
• http://www.livescience.com/40035-fusion-energy-gets-closer-to-reality.html

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)

Two reactions should have the same energy

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)

Good question. One source for much of this information is http://wwwppd.nrl.navy.mil/nrlformulary/NRL_FORMULARY_07.pdf, p. 44, which lists the reaction in question (our 6iii, their 5c) as

He-3 + T → He-5 (2.4 MeV) + p (11.9 MeV)

He-5 does in fact decay extremely quickly into He-4 + n, but the argument I (!) gave just above under #3He-T_fusion about how the energy is split up is wrong. Even ignoring how the energy is divided between He-4 and n, there is still a problem.

I think the problem is a mistake in the Formulary. If the He-5 has not 2.4 Mev but 0.24 Mev, then the energy for the two reactions is the same, and the energy is divided between the products in inverse proportion to the masses, as it must from conservation of momentum.

Ideally we would verify this with another source (and notify Huba), but I think it is clear enough that we can try to fix it right away. The question is, how? I would vote for concentrating on the end products and just striking (6iii), but people more interested in nuclear physics than fusion energy might like to know that there is a He-5 there, albeit short-lived. I could dish up a new improved argument about how the energy is divided between He-4 and n, but it will always look funny to list the same reactants and products twice.

Art Carlson (talk) 21:35, 3 December 2012 (UTC)

I'd suggest that this level of detail, the intermediate product need not be mentioned-- it's just a different path to get to the same end products. Geoffrey.landis (talk) 02:51, 4 December 2012 (UTC)

Done. Art Carlson (talk) 07:46, 4 December 2012 (UTC)

plagiarism

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.

It appears that the book may have copied Wikipedia. This version of the article from 2006 predates the 2007 copyright date of the book. I would also ask if content from Wikipedia may be used in a copyrighted text; I believe our license allows unlimited re-use. This may still require further inspection. Wikipedia talk:Copyright problems appears to be active enough to solicit for opinion. Tiderolls 19:10, 24 December 2012 (UTC)

reaction cross sections

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)

Nuclear fusion hits energy milestone

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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Are we correctly representing the basic roles of the strong interaction, tunneling effects, and KE?

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)

Great work on the list of plausibly exothermic terrestrial fusion reactions

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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"Nuclear Binding Energy Curve" Mislabeled

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)

I suspect that this is the usual case of everyone knows it, and so doesn't bother to say it. How much longer is the article if you add per nucleon to each one? How about if you say at the top that binding energies are always per nucleon? As for spontaneous fission, is it the usual quantum tunneling? I haven't thought about that for a while. Gah4 (talk) 03:09, 3 June 2018 (UTC)

Contradiction in lede

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)

You can fuse heavier nuclei if you supply enough energy, and this is commonly done for creating new heavy elements, mostly to make the periodic table longer. But if you want a fusion energy source (either slow or fast) you need an exothermic reaction. Creating heavy elements this way is not very productive, as with just a little more energy, it is enough to break apart the newly formed nucleus. Since you can't control so easily how they come together, production rate is very low. So, 99.99999999999999999999999999% of the time the statement is right. (New elements are claimed with only a few examples.) Gah4 (talk) 15:27, 1 September 2018 (UTC)

Okay, I went ahead and fixed the sentence in the first paragraph of the lede. Attic Salt (talk) 21:49, 4 September 2018 (UTC)

Here is a reference

References

Mimicking the sun's pressure waves & central region of fusion

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.

Some pressure waves are created without moving shields, simply with variation of the intensity of the magnets. a. It is very hard to impart the desired force on the pressure waves, b. Achieving strong enough pressure waves that make a difference, usually costumes way more energy than what we extract. (The pressure waves should be focused, not turbulent and arbitrary.)

note: correct harmonics DO MATTER!!! If you don't fine-tune the oscillations, you burn energy and money.

Greenhouse Item

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)

Neutrinos??

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)

Possible merge and redirect

The following discussion is closed. Please do not modify it. Subsequent comments should be made in a new section. A summary of the conclusions reached follows.

To merge Thermonuclear fusion into a distinct section in Nuclear fusion. Klbrain (talk) 10:06, 2 April 2023 (UTC)

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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)

i think that they should not as in the future they might have a breakthrough in technology might sepreate them both 82.113.249.177 (talk) 17:42, 26 January 2023 (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)

I agree with your point, but only if thermonuclear fusion becomes its own subsection, with other content that has already been mentioned in nuclear fusion being placed to appropriate sections. Nuclear fusion does not only figurate thermonuclear fusion, and other types of fusion, such as pycnonuclear, should be distinguished too (and merged too). The article also seems to disregard the various different types that authors have incorporated in their calculations of nuclear fusion rates - [1], [2] (thermonuclear w/ weak and strong screening, thermopycnonuclear, pycnonuclear), as examples, which further supports my point that distinction is still required. Mk0uQ (talk) 18:24, 9 August 2022 (UTC)

The discussion above is closed. Please do not modify it. Subsequent comments should be made on the appropriate discussion page. No further edits should be made to this discussion.

  Y Merger complete. Klbrain (talk) 11:28, 2 April 2023 (UTC)

The "Human body produces more heat than the sun"-falacy

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 ${\frac {3.8*10^{26}W}{4/3\pi \cdot 0.24\cdot 696,000,000m^{3}}}\approx 19.4mW/cm^{3}(=19.4kW/m^{3}$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)

Reaction rate - Units do not add up

Nuclear fusion#Requirements:

The reaction rate (fusions per volume per time) is ⟨σv⟩ times the product of the reactant number densities

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:

The volumetric reaction rate, that is, the number of reactions per unit time and per unit volume

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):

R = n*n*⟨σv⟩

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)