Talk:Plutonium-244

Hoffman et al. estimation of Pu-244 content in the rare-earth mineral bastnasite

It says that the they detected Pu-244 with a concentration of c₂₄₄ = 0.15×10⁻¹⁸ g/g in bastnasite, making its concentration 4.5 billion years ago in similar minerals 2⁵⁵ times larger or 3.6×10^-2 g/g, almost 5 times the pre-solar nebula abundance, relative to U-238, mentioned above. This seems erroneous and the differences in these estimates isn't explained. I sugest removing at least one of them. Crackhorace (talk) 17 November 2016

Second-shortest-lived primordial?

@Double sharp: I notice you edited in a mention of Sm-146 being primordial, but I don't see a source for it and can't find one myself. Could you enlighten me? Magic9mushroom (talk) 14:45, 24 August 2017 (UTC)

@Magic9mushroom: I think that was fairly old, before the half-life of ¹⁴⁶Sm was more accurately determined to be lower than that of ²⁴⁴Pu. I'll remove it; thanks for alerting me! Double sharp (talk) 14:50, 24 August 2017 (UTC)

@Double sharp: So you're saying Sm-146 is not in fact primordial? I mean, certainly if Sm-146 is primordial Pu-244 would be the second-shortest-lived primordial; I'm more concerned with whether Sm-146 has or hasn't been confirmed to be primordial. Back-of-the-envelope calculations suggest there should be about 4 mg left in the entire Earth, so it's in the weird limbo where there is some but no conceivable experiment could detect it (a kilogram of natural samarium should contain about 9 atoms of Sm-246 and have about one decay every 10 million years). Magic9mushroom (talk) 02:44, 25 August 2017 (UTC)

@Magic9mushroom: Well, Pu-244 and Sm-146 probably are primordial in the abstract sense. However, I don't think we should list them without some confirmatory experiments. There may have been citations for Sm-146 being primordial here at some point; I really don't remember. Perhaps isotopes of samarium has it. Double sharp (talk) 03:11, 25 August 2017 (UTC)

@Magic9mushroom: Ah, I found a source (doi 10.1039/B608157F). It says that ¹⁴⁶Sm should be primordial, as you note, but it should not be easy to find, especially because mass spectrometry is going to get swamped by the stable isobar ¹⁴⁶Nd. So they propose here a method to effectively separate Nd from Sm and pin it down; but since even the detection of ²⁴⁴Pu is unconfirmed, we may have to wait a while to find ¹⁴⁶Sm. They also suggest that a similar Hf–W separation should help to find ¹⁸²Hf, which may be around from more recent nearby supernovae like ⁶⁰Fe. So, perhaps we may finally get rid of these two borderline cases in the future, though I am not inclined to be as hopeful given that this paper is from 2006. Double sharp (talk) 03:40, 25 August 2017 (UTC)

@Double sharp: That paper still assumes a 100-million-year half-life, which means it's probably overestimating the abundance of Sm-146 in the present day.

I'm going to remove the mention of Sm-146 being detected from the Isotopes of niobium article, because it's not sourced there either and was edited by an IP from a sentence originally talking about Pu-244. I think this article could do with some cleanup as well; there's one paragraph stating unambiguously that Pu-244 is primordial and a second saying that it's disputed, which frankly stinks. And lastly, I think Isotopes of samarium should probably have the bit saying Sm-146 definitively isn't primordial reworded. Your thoughts on the latter two? Magic9mushroom (talk) 06:35, 25 August 2017 (UTC)

@Magic9mushroom: I would suggest that we start, for both Pu-244 and Sm-146, by stating how much of these isotopes we should expect to have left today, and thus noting that they should be primordial. Then we can talk about the reports (or lack thereof) of their primordialness, and whether or not they have been confirmed. Do you think that would be a better approach?

As for general coverage that is not specifically about Pu-244 and Sm-146 and simply discusses primordial nuclides and gives an offhand number, I would stick to the status quo and simply consider U-235 the shortest-lived primordial for those purposes until we have some experimental confirmation of these two. Double sharp (talk) 07:14, 25 August 2017 (UTC)

@Double sharp: Well, I don't have a source for how much ¹⁴⁶Sm is expected to be on Earth; the paper issuing a revised half-life for ¹⁴⁶Sm gives a half-life, an age of the Earth and an initial solar ratio of ¹⁴⁶Sm/¹⁴⁴Sm, but to get an estimate from that involves synthesis with samarium elemental abundance and ¹⁴⁴Sm isotopic abundance from other sources. That's why I said it's back-of-the-envelope. For ²⁴⁴Pu I'm not even sure it can be theoretically calculated at this time; ²⁴⁴Pu doesn't produce detectable isotopic-abundance anomalies (it's 4n, so it decays to ²³²Th... which is mononuclidic), and our theoretical understanding of the r-process is limited in the actinide region, so there's no way to calculate how much ²⁴⁴Pu was there at Sol's formation absent direct observation of how much is here now.

With respect to the broader articles, I agree with listing ²³⁵U as the shortest-lived in tables, since it's both the shortest-lived confirmed primordial and the shortest-lived primordial existing in useful quantities (billions of tonnes compared to maybe grams for ²⁴⁴Pu and milligrams for ¹⁴⁶Sm), but I don't think e.g. the note about ²⁴⁴Pu and ¹⁴⁶Sm in the Primordial nuclide article itself needs removing entirely. Magic9mushroom (talk) 08:36, 25 August 2017 (UTC)

@Magic9mushroom: Well, at the very least, we can say that some minute quantities of Pu-244 and Sm-146 should persist today, citing that 2006 paper, and continue as before. In your example, the primordial nuclides are the subject of discussion, so these two borderline cases are certainly on-topic. Double sharp (talk) 09:00, 25 August 2017 (UTC)

Does this isotope even exist?

...since even the detection of 244Pu is unconfirmed, ... according to User:Double sharp. Plutonium-239 is the most stable isotope known in any measurable quantity, and somebody's shooting billiards for 150 neutrons in the nucleus and it just doesn't happen at all, let alone stable for 80,000,000 years. 24.237.158.249 (talk) 17:28, 11 January 2022 (UTC)

Plutonium-244 most certainly exists and is well-characterized, and it has been detected in the interstellar medium (possibly with some cosmogenic traces on Earth). Rather, the detection of ²⁴⁴
Pu
in nature as a primordial nuclide is unconfirmed. Indeed, ²³⁹
Pu
is the most available isotope and the one used in nuclear reactors and weapons, but its half-life is certainly too short to be primordial – traces of it exist in nature due to neutron capture on ²³⁸
U
. ComplexRational (talk) 19:39, 11 January 2022 (UTC)

You say "detected in the interstellar medium" but that's all theory with the gravitational red shift and inferred properties. Nothing to back it up. Pu-239 on the other hand exists. There's a photo. You can just pick up a chunk of it in your hand. Heavy as solid gold, but then your fingers tingle, and start burning after about 5 seconds, it aches all the way in your bones, you get sick, have diarrhea, you hair starts falling out etc. It's already at the point of blowing up with 145 neutrons in the nucleus to 94 protons. You can't just add 5 more neutrons to a nucleus that's already highly unstable and say the whole mess of subatomic particles is likely as not to stay together in one nucleus for tens millions of years. 24.237.158.249 (talk) 23:05, 11 January 2022 (UTC)

Actually, you can. And stars can even better. See [1] [2], among many others, to back up these "theories". ComplexRational (talk) 00:37, 12 January 2022 (UTC)

By this logic, U-238 shouldn't exist either. U-232 is so unstable, how can adding six neutrons help it? It's not really that simple. :D

Pu-244 has been detected on Earth. Admittedly most of it we made ourselves through high-flux reactors and thermonuclear detonations. Here's more about producing it. There's tinier traces that likely came from space. What I meant in context was that no one has actually incontrovertibly detected Pu-244 that must have survived from the formation of the Earth. But that's different. Double sharp (talk) 02:59, 12 January 2022 (UTC)

Actually the thing goes the other way round. When you don't go across the magic numbers, nuclides having more neutrons are more stable with respect to alpha decay. The reason is basically that alpha decay, which releases two protons and two neutrons, increases the neutron-proton ratio, so the neutron-deficient nuclides undergo alpha decay more easily.

Considering alpha and beta decays at the same time, the most stable isotope of an element should generally be the heaviest beta-stable one (²²²Rn, ²²⁶Ra, ²³²Th, ²³⁸U, ²⁴⁴Pu, ²⁴⁷Cm, ...; ²²²Rn is not beta-stable but has theoretical beta half-life 7 orders longer than its alpha half-life; perhaps 10-11 for ²⁴⁷Cm) However, from element 98 (Cf) on, the heaviest beta-stable isotope (^{256 or 258}Cf, ^{260 or 262}Fm, ^{266 or 268}No) undergo SF quickly (half-lives usually at the order of miliseconds). 14.52.231.91 (talk) 00:26, 16 August 2024 (UTC)