Talk:Tritium

Mystery reactions

[tritium is produced] by D(n,gamma)T) and 10B(n,t)8Be

I have no idea what this is supposed to mean; presumably it's some abbreviated description of nuclear reactions, but it's pretty impenetrable. If someone can clarify this, it can go back in. --Andrew 04:07, Apr 20, 2005 (UTC)

This is shorthand for nuclear bombardments

D(n,gamma)T means that Deuterium is bombarded with a neutron and releases gamma rays to become Tritium. 10B(n,t)8Be means that Boron-10 is bombarded with a neutron and releases a Tritium atom to become Beryllium-8. Both of these reactions produce Tritium. — oo64eva (AJ) ^{(U | T | C)} @ 04:18, Apr 20, 2005 (UTC)

Reaction of a neutron with lithium-6

Can someone explain why when one hits lithium-6 with neurons it gives helium and tritium instead of giving lithim-7, which is at a lower energy? Eric Kvaalen (talk) 15:56, 16 October 2022 (UTC)

@Eric Kvaalen: This is due to the fact that lithium-6 has a relatively low nuclear binding energy of ~5.6 MeV/nucleon, though the exact mechanism would also depend on the energy (temperature) of the incident neutron. If a neutron collides with lithium-6 and has a high enough "temperature" such that this binding energy is exceeded, the collision has a higher probability of inducing fission into lighter nuclei rather than fusion into lithium-7, so the neutron-capture cross section drops. Additionally, helium-4 is very stable, while lithium-7 is also fragile, and such nuclear processes tend to favor formation of more tightly bound and/or magic nuclei. This is also the reason why lithium is present in brown dwarfs but is destroyed in main sequence stars; the temperature inside main sequence stars is high enough such that collisions of neutrons with lithium cause it to be destroyed faster than it is created. ^Complex/_Rational 22:28, 16 October 2022 (UTC)

@ComplexRational: Thanks for the reply. If I understand you correctly, you're saying that a good portion of the neutrons are absorbed, giving ⁷Li, and that the amount depends on the energy of the neutron. That seems a bit strange, since I've never heard anyone talk about that in the context of blanketing a fusion reactor in order to create tritium. Can you give a reference so we can put that into the article? Also, I don't understand what you say about the helium being very stable andn the ⁷Li being fragile. As I said, ⁷Li is more stable (lower energy) than the combination of a helium and a tritium. Isn't that what counts in the end? Eric Kvaalen (talk) 10:50, 17 October 2022 (UTC)

By "stable", I was referring to binding energy, and the fact that ⁴He is also a doubly magic nucleus – although the ⁷Li nucleus is stable, the required energy to break it apart is much less than for ⁴He. Indeed, the absorption cross section is dependent on energy, though I'm not very familiar with the concept of "blanketing" a fusion reactor.

One article describing this reaction and the production of tritium is [1] – it specifically describes the reaction ⁶Li + n → ⁴He + ³H, as well as its threshold energy. I hope this helps. ^Complex/_Rational 15:14, 17 October 2022 (UTC)

I should also clarify, while The production of tritium from lithium-6 in such breeder ceramics is possible with neutrons of any energy, the yield is affected by neutron temperature. ^Complex/_Rational 17:33, 17 October 2022 (UTC)

I slightly tweaked the text and added that reference. ^Complex/_Rational 17:42, 17 October 2022 (UTC)

@ComplexRational: I don't understand what you mean by the required energy to break apart a ⁷Li nucleus.

The question is whether neutron absorption happens. That article doesn't mention it when it talks about side reactions (reactions 15 through 17).

And I don't understand what is meant by the threshold energy. If the reaction that produces tritium happens with thermal neutrons, doesn't that mean that the threshold energy is zero? Why should there be a threshold energy for an exothermic reaction with no electrostatic repulsion between the reactants? I think it's a mistake. Notice that the value (2.47 MeV) is exactly the energy needed for reaction 9 (producing tritium from ⁷Li), which means it's approximately the threshold energy for that reaction, not for the reaction with ⁶Li! Eric Kvaalen (talk) 09:34, 23 October 2022 (UTC)

Threshold energy is the minimum kinetic energy needed to overcome a "threshold" for a reaction to proceed. Reaction 8 specifies a threshold energy of 2.47 MeV for the reaction starting from ⁶Li; I'm unsure if it's a coincidence that the same value also occurs in reaction 9. Regarding it being an exothermic reaction is that there's a net energy release, though a certain energy is required to trigger the reaction; I believe this is similar to the notion of activation energy in chemical reactions. (The alternative would be a spontaneous reaction, but ⁷Li cannot and indeed does not undergo spontaneous fission into T and ⁴He.) However, I may have misunderstood the part about thermal neutron cross section, so I'll undo that part of my addition, and feel free to further refine the text as you see fit. ^Complex/_Rational 14:54, 23 October 2022 (UTC)

@ComplexRational: I'm sure it's correct that the cross section is highest for thermal neutrons -- the article says so almost explicitly. I've put that part back into the Tritium article, but I've taken out the thing about a threshold energy. I will try to contact the author to ask about it. Eric Kvaalen (talk) 10:19, 24 October 2022 (UTC)

@ComplexRational: I wrote to Marek Rubel, and he confirms that it's an error, adding "Of course, there is no E(th) for Li-6". He says the mistake was spotted too late in the editorial process to be corrected. Eric Kvaalen (talk) 05:52, 27 October 2022 (UTC)

Good to know, so thanks for catching that. I'll see if I can find additional/better sources describing this process to add. ^Complex/_Rational 12:13, 27 October 2022 (UTC)

@ComplexRational: I think I now know the answer to my question. In the article Nuclear fusion it says that one of the desired properties of a nuclear fusion reaction is that it should give two or more products because "This allows simultaneous conservation of energy and momentum without relying on the electromagnetic force." So apparently if there's only one product, such as ⁷Li, then the rate (or "cross section" as one says) is small, because the electromagnetic force is too weak and the product would have to lose the extra energy via the electromagnetic force in the form of a gamma ray. Basic'ly, the glob formed by the collision of the neutron with the ⁶Li, even if it occurs with a thermal neutron, has too much energy to become ⁷Li and "prefers" to undergo fission instead. This is similar to what happens with ²³⁵U when it absorbs a neutron. It undergoes fission rather than becoming ²³⁶U, which is fairly stable (half-life of 23 million years). Eric Kvaalen (talk) 19:10, 12 February 2024 (UTC)

Clutter out

In the section "Production", subsection "Lithium", i edited the wikicode for the nuclear reactions, so that it is vastly more concise. I think un-concise wikicode looks ugly. In the process i also changed the notation for tritium from "T" to "³H"; to be in line with what IUPAC recommends, and with the idea of a single chemical symbol for each element, a practise which is followed (with at most a few exceptions) for every element other than hydrogen. Okay?--Solomonfromfinland (talk) 03:46, 28 May 2024 (UTC)

I also removed similar clutter in the subsection "Boron".--Solomonfromfinland (talk) 04:18, 28 May 2024 (UTC)

Misleading image

As of 7/22/23, the first image in the article shows a nucleus with 2 red spheres and 1 blue sphere. Graphic depictions of atoms conventionally color proteins red and neutrons blue/black, so the image appears to show Helium-3 instead. Marchantiophyta (talk) 15:14, 22 July 2023 (UTC)

Globalize not needed

Tritium#Environmental contamination currently has a globalize template. It does not quite make sense because:

• US makes a lot of the reactor models sold globally, so the amounts should make sense anywhere; we have a "Annual discharge of tritium from nuclear facilities" template anyways
• Improperly disposed signs will leak regardless of country

Artoria2e5 🌉 01:59, 25 August 2023 (UTC)

Inconsistency or wording?

In Properties it says "Combined with oxygen, it forms a liquid called tritiated water (T2O)." Then in Health Risks it says "Tritium is an isotope of hydrogen, which allows it to readily bind to hydroxyl radicals, forming tritiated water (HTO), and two carbon atoms.", followed by frequent use of "HTO" in the rest of the Health Risks section. My chemistry knowledge is limited, so is it T2O or HTO? Or are they different and I'm misunderstanding the sentence about binding with hydroxyl radicals? MajorBean (talk) 15:55, 28 August 2023 (UTC)

The chemical formula T2O means that the water molecule contains two tritium atoms, while HTO means that only one of the two hydrogen atoms in the molecule is tritium, the other being "normal" hydrogen. So it's two different types of molecules which are both called "tritiated water" here.Roentgenium111 (talk) 17:57, 28 August 2023 (UTC)