fullsquare

so on top of that 1%-ish gallium (which stabilizes delta phase, the least dense one, that collapses under pressure to alpha, the most dense one, which allows slightly less compression to be used, and this means more compact weapons), which would need to be separated before that plutonium gets turned into MOX, i understand that most of american plutonium stockpiles are somewhere around 94% 239Pu, and some are 97%+. i guess they're selling the worst stuff, which would make little difference for reactors, and if there's anything that american military is good at, it's logistics. on production side, the very shortened story is that we start with uranium and irradiate it, which gives

238U (n,gamma) 239U (beta) 239Np (beta) 239Pu

and that's it. but it really is a bit more complicated, because first, nothing stops that just made plutonium from reacting further, so some of it will fission which means that it can't be recovered, but it also means more neutrons, which will also make some plutonium, so it's not all bad. but not all plutonium will fission, and so there's entire series of reactions:

239Pu (n,gamma) 240Pu (n,gamma) 241Pu (n,gamma) 242Pu (n,gamma) 243Pu

at this point reaction stops because 243Pu is very short-lived, and it decays into 243Am. at the same time, if neutrons react without leaving fuel pin, they won't be slowed down much, which means another reaction is possible (but much less likely):

242Pu (n,2n) 241Pu (n,2n) 240Pu (n,2n) 239Pu (n,2n) 238Pu

there's also 238U (n,2n) 237U (beta) 237Np (n,gamma) 238Np (beta) 238Pu

of these, 238Pu and 240Pu have unacceptably high neutron emission rate, which means that if there's too much of these nuclear weapon is likely to predetonate. because the most important use of plutonium in modern advanced thermonuclear weapons is in primary, this means that it could be so that entire weapon fails to function if there's too much of these contaminants (low-kt or even sub-kt yield instead of, say, 350kt). of these, 238Pu and 241Pu have short halflives, which means that plutonium containing these will heat up with considerable power. this can damage explosives bonded to it. 240Pu is additionally a radiation hazard because of neutrons emitted, but it's only really relevant for submarine crews. this is why these weapons use the better 97%+ grade plutonium, and additionally some of that 97% grade was made in order to blend with some older, worse quality stocks

there's remarkably few parameters that can be used in order to steer these reactions in the way we want. about the only relevant one here would be neutron temperature, which is really chosen at reactor design stage and increasing it means that neutron capture is less likely. this makes fission more likely, more neutrons are present and more plutonium can be formed. this also turns reactor into fast reactor which are notoriously hard to build and iirc only russia and india operate large fast reactors today. short of that, about the only way to prevent 239Pu from reacting further is to take it out of there, which means low burnup and only tiny amounts can be recovered per run. from what i understand, the choice of 94%-ish 239Pu content is end effect of massive optimization problem focused on how to make a pit at the lowest price. this includes all the (expensive, slightly dangerous) labour it takes in reprocessing fuel and how required pit mass increases with lower quality plutonium

little of that matters when running a powerplant. some isotopes being neutron emitters are actually an advantage because it makes startup smoother. the longer fuel stays in reactor the less fissile plutonium there is as a result, and the more advanced reactors allowing higher burnups make plutonium recovery less attractive, or, in other words, most of benefit of recovering plutonium in order to put it in new fuel can be realized just by leaving fuel in reactor for longer time in the first place. in regular light water reactor, steady state develops where plutonium is formed as fast as it is consumed, and it accounts for about third of energy released when that steady state sets in. this also means that about third of fissile uranium can be replaced by fissile plutonium with no modifications to reactor

on top of weapons use, some countries do reprocessing anyway as a matter of policy as a hedge against future shortages of uranium. some of these schemes require fast reactors which can burn these isotopes useless in regular reactor and make fresh, weapons grade almost pure 239Pu, which limits countries that can make it work, by diplomatic means, only to already established nuclear powers, and labour costs needed for its operation limit it to currently only india and russia, and formerly france. this is because at any burnup, in best case plutonium can be only separated once from light water reactor fuel and used in light water reactor. after that, plutonium quality is too low to be useful this way

in comparison to reactor grade plutonium, weapons grade plutonium would allow to make more fuel per kg of this material, but also it would be astronomically expensive compared to regular stuff, which is already unprofitable for power generation in countries with western labour costs, unless it's a fire sale. the second problem is that if more than this 1/3 of fissile isotopes in fresh fuel is plutonium, then generally reactors would need recertification or maybe completely new design, because plutonium gives less delayed neutrons which are critical for smooth control of reactor power. this is, mind you, in context of country that practically stopped building new nuclear powerplants. if small reactors are on the table, then these naturally need higher amount of fissile isotopes, like 20-30%, and something tells me people involved would like to try this

another thing to note here is that there's an old american policy in place that forbids (domestic) plutonium recovery for alleged (international) nonproliferation reasons. i don't believe this is the case, it makes zero sense, and instead i think that nuclear industry wanted a way out of that money pit without state backing, because plutonium recovery and reuse for power generation is more expensive than just buying more uranium, sustainability of this energy source and volume needed for nuclear waste be damned. they could get away with this because military weapons grade plutonium stockpiles were assessed as sufficient. now they're pawning heirloom nukes to monorail salesmen instead

every batch of plutonium is made mostly out of Pu-239 that's just how plutonium works. it can't be separated into isotopes in any meaningful amounts so any batch of plutonium is also a mix of a couple of isotopes. reactor grade might be something like 55% Pu-239 plus say 12% also fissile Pu-241 with the rest being nonfissile Pu-240, Pu-242 and Pu-238 in that order. the newer reactor and fuel pin design, the higher burnup and the less fissile isotopes will be present at the end of the cycle. even in purely uranium fueled reactor about third of energy at the end of the fuel cycle comes from plutonium bred in the same fuel pin. i can elaborate on that if you want to

this shouldn't be surprising if you paid any amount of attention https://en.wikipedia.org/wiki/Pravda_network https://www.france24.com/en/live-news/20250310-russian-disinformation-infects-ai-chatbots-researchers-warn

i don't think so, it's like megatons to megawatts but stupider, instead of using up uranium from adversary they want to use up their own plutonium, while also having policies against spent fuel reprocessing (for alleged nonproliferation reasons, which is patently bullshit, power generation was straight up cheaper this way because new uranium is cheaper than reprocessing and use of mox. some other countries (at minimum ru, fr, in, pk, jp, cn, il) do reprocessing as a matter of national security/energy independence/hedge against future shortages of uranium). also this requires recertification of reactors for mox use, which won't always work or else only part of uranium can be replaced, and if it's for smr, then there's gonna be a lot of plutonium in there, and it all starts with handing plutonium to motherfucking sam altman, for only a slight chance of any positive results

i see it more as current administration ripping copper wiring from walls than anything else tbh

in my country it used to be like this for 50 years, you get flat rate per day, counted up to fractions of day, separately for accomodation and food + everything else. you only have to keep transportation tickets

behold, disruption

i don't mean beta-oxidation, it's just a series of separated normal reactions. i mean something like this: when first learning about ketones, you might learn about aldol condensation, which has enol as a nucleophile and another carbonyl as electrophile. at some other point you might learn about strecker reaction, which has iminium ion as electrophile and cyanide as nucleophile. but really, what you can do is mix and match, and you can pair enolizable ketone and iminium (mannich reaction) or carbonyl and cyanide (cyanohydrin formation) and then generalize, for example you don't need strictly ketone for mannich, you can use any electron rich conjugated system like malonate or nitroalkane anion (henry reaction) or phenol or indole. to figure this out you need to study mechanisms. these last two are usually treated as variants of friedel-crafts reaction, but really categories like this are fake

and to get that right, you need to know how these reactive intermediates look like, how reactive they are, what influences their stability which means that ochem starts with discussion of carbocations, carboanions, radicals, their shapes and orbitals involved, hyperconjugation, solvent effects and the like. and then first reactions taught are sn1/sn2, because these showcase these fundamentals nicely, and from there, it's about introduction of more compound classes

we only had synthons introduced during lecture at around 4th year, and only for ochem path, it's not doing a lot at that point and imo would have much more impact right after ochem intro course

there was also yolo minneapolis, or whatever was his name i don't think he was relevant since covid

i always thought that the idea of synthons should be taught early on https://en.wikipedia.org/wiki/Synthon

i'd say it's more important to learn mechanisms because this way you can notice these patterns of reactivity easier. at some point you'd only get new reactions that are really just pieces of other reactions you know put in a new way

there's zero reason to make chart like this, it's both barely comprehensible and touching surface level stuff only (where are palladium couplings for one)

i mean it would be hard to imagine 20 years ago precise ways things could get worse, and then