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You return an equal amount of the same element after you buy/produce some, you don't return the exact same molecules...
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Oct 24, 2019 16:28
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Carbon dioxide posted:My thoughts: "Cf? I do not recognize that symbol right away... " *googles* "...oh. Oh. OH." I must be missing something then. Why is this stuff so dangerous?
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Oct 24, 2019 17:27
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Or, alternatively, you return the same atoms, with a disclaimer that some of them may have shrunk in the wash.
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Oct 24, 2019 17:29
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It would make sense to me that you return the vial or whatever with the rest of the stuff and whatever the other bit happened to have decayed into?Nebakenezzer posted:I must be missing something then. Why is this stuff so dangerous? All the neutrons it poops out?
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Oct 24, 2019 17:39
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At uni, we treated our californium sources like senior staff members.
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Oct 24, 2019 18:26
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Groda posted:At uni, we treated our californium sources like senior staff members. As in they got a little bit smaller and stranger as they approach retirement?
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Oct 24, 2019 18:55
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Nebakenezzer posted:I must be missing something then. Why is this stuff so dangerous? 540 times as radioactive as a similar amount of radium, and it's spitting out neutrons instead of alphas and or betas.
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Oct 24, 2019 20:38
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Phanatic posted:540 times as radioactive as a similar amount of radium, and it's spitting out neutrons instead of alphas and or betas.  Yeah, I have some holes in my understanding of radioactivity, I didn't really get that ionizing radiation could be a number of different physical processes. So why are neutrons worse than other particle radiation?
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Oct 24, 2019 21:11
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Nebakenezzer posted:
Penetrating power. It will get quite a ways into you before finally interacting with something, and if that thing happens to be a DNA molecule it will gently caress you up.
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Oct 24, 2019 21:14
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Ah. I get the gigantic containment vessel now.
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Oct 24, 2019 21:27
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Nebakenezzer posted:Yeah, I have some holes in my understanding of radioactivity, I didn't really get that ionizing radiation could be a number of different physical processes. Massive and chargeless. Radiation chiefly screws with you by smacking into water molecules in your cells, ionizing them and creating a cascade of reactive oxygen species that wind up doing bad things to that cell's DNA. Alpha particles are very massive, but they also have that +2 charge, so they strongly interact with the first thing they come along with. Since that's usually the air, or your dead skin layers, they're not really a concern unless you ingest something that emits alphas. Betas also have that -1 charge, and the mass of a beta is really small, so they also tend to interact pretty strongly but don't have as much kinetic energy to work with. Neutrons are both fairly massive, and uncharged, so they're able to go right through stuff that will block alphas or betas and will bounce off all those hydrogens in your cells. It's because not all radiation is created equal that you convert from absorbed dose to equivalent dose by multiplying the former by weighting factor based on the type of radiation you were hit with. One gray of gamma radiation, the weighting factor is one, you just took a dose of one sievert. If you somehow inhaled enough alpha emitters to absorb one gray of alphas, the weighting factor is 20 and you just took a dose of 20 sieverts and you dead. The weighting factor for neutrons depends on neutron energy, but for most decays it's in the range of 5-15.
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Oct 24, 2019 21:33
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Neutron radiation has the unwelcome property of making things it hits radioactive via neutron activation. Mind also that a critical sphere of Cf-252 is only 69 mm in diameter.
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Oct 24, 2019 21:33
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Platystemon posted:Neutron radiation has the unwelcome property of making things it hits radioactive via neutron activation. nice
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Oct 24, 2019 21:40
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Cool it's time for health physics. I did my master's thesis on alpha particles. (this is related to neutrons so bear with me) Heavy charged particles like alphas are bad for you but they don't penetrate very well. So an alpha emitter up against your skin won't penetrate far enough for its alphas to reach the basal cell layer that is vulnerable to radiation, they will just pass through the cells that are supposed to die soon anyway. However, ingesting an alpha emitter will put it right up against vulnerable cells. An alpha emitter that gets into your lungs as inhaled dust or as radon gas will emit alphas that pass through several vulnerable lung tissue cells before stopping, making this stuff very dangerous to ingest. The cool thing about neutrons is that they have reactions with mid-size nuclei that spit out heavy charged particles like protons and alphas. One of the types of nuclei that has a high chance of spitting out alphas when neutrons strike it is carbon, which the body has no shortage of. So a human body getting irradiated with neutrons has health effects similar to said body having alpha emitters everywhere inside it. That's why the radiation weighting factor for neutrons at certain energies is essentially the same as the weighting factor for alphas. Also neutron activation can cause things to become radioactive, but this isn't really the primary reason why neutrons are directly dangerous to people (it makes operating and decommissioning a nuclear reactor more annoying though.) However, activation of certain things in the human body like sulfur can be used in post-accident dosimetry to find out how badly someone got blasted.
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Oct 24, 2019 21:41
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A good explainer that got stuck in my head the last time radiation blasted through the thread was the four cookie test: Suppose you have four cookies, each one emits one of alpha, beta, gamma, and neutron radiation. You have to decide which one to eat, which one to put into your pocket, which one to hold in your hand, and which one to throw away. You put the beta cookie in your pocket (beta particles, or electrons, are effectively blocked by one layer of clothing), hold the alpha cookie in your hand (an alpha, being a bare Helium nucleus, is stopped by the dead layer of skin), eat the gamma cookie (it'll give you the same dose in any case) and throw the neutron cookie away before it fucks you up any further just by being near it.
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Oct 24, 2019 22:02
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Also why alphas (and by extension neutrons, because of the aforementioned nuclear reaction that spits out alphas) are so dangerous is because of this: That's the Bragg curve of alphas in tissue-equivalent material at a similar density to that of the real thing. The particle only travels about 40 microns but it has a stopping power greater than 100 keV/microns at nearly all points along its path.  That's a plot of the RBE (Relative Biological Effectiveness) of a particle given its unrestricted LET (same thing as stopping power.) RBE is how many times more dangerous the radiation is than photon radiation of the same energy (more or less). It shows that particles with an LET of 100 keV/micron is about the most dangerous it can possibly be though the data doesn't always agree as to how much that maximum is. The falloff after 100 keV/micron isn't because the particle is less dangerous, but because it "wastes" energy on overkill. So alphas are essentially as dangerous as possible to cells at all points along their path. You just need to find a way to get them into your body, but neutrons make it easy.
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Oct 24, 2019 22:02
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I’ll gladly pay you Tuesday for a heavy element today
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Oct 24, 2019 22:44
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BattleMaster posted:One of the types of nuclei that has a high chance of spitting out alphas when neutrons strike it is carbon, which the body has no shortage of. Hrm? Carbon-12 should just absorb a neutron to turn into C-13, which is stable. Even if it manages to hit a C-14 nucleus and turn it into C-15, C-15's a beta emitter.
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Oct 24, 2019 22:54
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Phanatic posted:Hrm? A lot more n+12C reactions exist than plain absorption, especially when the neutrons have a bunch of energy:  From https://www.tandfonline.com/doi/pdf/10.1080/18811248.1997.9733638 You can see this in microdosimetry when you subject a tissue-equivalent proportional counter to neutron irradiation and calculate the lineal (not linear) energy and bin it logarithmically weighted by energy like so:  The large peak is from protons that get knocked out of the tissue-equivalent plastic that makes up the shell of the counter, while the smaller fatter peak to the right of it is from alphas that get knocked out of it. This happens in a human body too, you get protons and alphas flying around inside your cells when you get zapped by fast neutrons. edit: if thermal neutron absorption was the only thing that happened to you when you got hit by neutrons, it would be a lot safer. Not great, but not terrible BattleMaster has a new favorite as of 02:15 on Oct 25, 2019 |
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Oct 24, 2019 23:06
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Why don't we see more proton emission anyways? It's always neutrons and electrons and helium nuclei.
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Oct 24, 2019 23:10
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So is Cf the most radiologically dangerous (relatively stable) element?
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Oct 24, 2019 23:17
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aphid_licker posted:It would make sense to me that you return the vial or whatever with the rest of the stuff and whatever the other bit happened to have decayed into? "Here's what's left of the californium you loaned us." (Indicates 50-ton containment vessel) "A bunch of neutrons popped out and got lost so here are some extra neutrons to replace them." (Hands over tiny block of lead) "They're mixed in with some protons and electrons, but you guys are probably better at purifying this stuff than we are"
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Oct 24, 2019 23:51
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Low energy neutrons are not so bad. But they can interact with certain nuclides and release radiation, just really not the ones in your tissue that much. But that means you can make an agent that contains those nuclides, localise it in a tumour and then use thermal neutrons to generate alpha particles in the tumour. Eg boron 10 for some alpha particles. Or gadolinium 157 for beta like particles. But not actually betas, just specific sort of short range electrons with high LET.
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Oct 25, 2019 00:01
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https://twitter.com/fab_hinz/status/1187407893626159104
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Oct 25, 2019 05:44
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The last couple of video have some hardcore nuclear chemistry at Oak Ridge National Laboratory. https://www.youtube.com/watch?v=S5nFHMKCA00 MOOOO. Fresh milk. This is for Actinium which is absurdly radioactive due to it's short half life. It's active enough to glow even though there for a ng. https://www.youtube.com/watch?v=DmczVhGq8cU Sub to the channel, it's legit good.
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Oct 25, 2019 06:29
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Arglebargle III posted:Why don't we see more proton emission anyways? It's always neutrons and electrons and helium nuclei. If a nucleus is capable of emitting a proton, it typically does so quickly enough that the nucleus never sticks around long enough to say it technically 'exists' so much as it 'was an event'.
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Oct 25, 2019 07:36
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silentsnack posted:An alpha is more stable (binding energy per nucleon) and has a lower charge-to-mass ratio so the threshold energy for an alpha to escape a heavy nucleus is lower. "Its existence was an event" sounds like a pretty  way to live your half life.
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Oct 25, 2019 11:26
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isn't a nucleus ejecting protons called "fission"
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Oct 25, 2019 11:47
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Zereth posted:isn't a nucleus ejecting protons called "fission" In strict terms, radioactive decay can shave off alpha particles, too. Fission is when you split an atom in to two parts. Alpha particles and neutrons tend to result when you shear a nucleus apart. I guess if you include helium as a fissile product, Alpha decay is fission. 
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Oct 25, 2019 12:26
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BattleMaster posted:A lot more n+12C reactions exist than plain absorption, especially when the neutrons have a bunch of energy: Love the one with the C just giving up and exploding into three alphas
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Oct 25, 2019 16:26
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Intoluene posted:In strict terms, radioactive decay can shave off alpha particles, too. Fission is when you split an atom in to two parts. Two or more parts. Ternary fission is relatively rare, but it happens. quote:I guess if you include helium as a fissile product, Alpha decay is fission. Alpha decay is pretty much a special case of spontaneous fission. It's a quantum-tunneling process. You've got the strong force trying to hold all the nucleons together, and you've got electrostatic repulsion between the protons trying to fly them apart, and usually they're in a potential well deep enough that they can't get out. But they can quantum-tunnel out of that well and escape.
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Oct 25, 2019 17:02
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Can someone else confirm that before I have a positive reaction to a Phanatic post
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Oct 25, 2019 17:31
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Captain Foo posted:Can someone else confirm that before I have a positive reaction to a Phanatic post I can confirm that at least in this instance phanatic is slightly more than just barely technically right about something. All radioactive decay can be modeled as quantum tunneling processes because everything is quantum mechanics at the subatomic scale.
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Oct 25, 2019 19:22
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silentsnack posted:All radioactive decay can be modeled as quantum tunneling processes because everything is quantum mechanics at the subatomic scale. Not all forms, no. Beta decay/inverse beta decay/electron capture are mediated by the weak force, it's an entirely different process.
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Oct 25, 2019 19:32
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Phanatic posted:Not all forms, no. Beta decay/inverse beta decay/electron capture are mediated by the weak force, it's an entirely different process. How do you read "Can be modeled as..." and interpret that as "...is exactly the literal scenario of a particle traveling through a potential barrier that results in an impossible state with negative kinetic energy" ? Beta decays have the 'forbidden quantum arithmetic' barrier.
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Oct 25, 2019 19:58
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silentsnack posted:How do you read "Can be modeled as..." and interpret that as "...is exactly the literal scenario of a particle traveling through a potential barrier that results in an impossible state with negative kinetic energy" ? A forbidden transition isn't at all the same thing as quantum tunneling. If you attempt to model beta decay as a quantum tunneling process, you will get the wrong answers, because your model does not correspond to what is happening. Beta decay is an entirely different process, and it cannot be modeled as quantum tunneling. Edit: Here's a specific example. You can effectively stimulate beta decay, which means you can actually change the half-life of isotopes that decay by beta emission. Rhenium-187 normally has a half-life of 42 billion years, but if fully-ionized Re-187 beta-decays with a half-life of only 33 years. If you model beta decay as quantum tunneling, your model is incapable of making that prediction. Phanatic has a new favorite as of 20:29 on Oct 25, 2019 |
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Oct 25, 2019 20:11
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Phanatic posted:Two or more parts. Ternary fission is relatively rare, but it happens. Didn't know about ternary fission. That's actually pretty cool.
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Oct 25, 2019 20:28
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Phanatic posted:A forbidden transition isn't at all the same thing as quantum tunneling. If you attempt to model beta decay as a quantum tunneling process, you will get the wrong answers, because your model does not correspond to what is happening. Beta decay is an entirely different process, and it cannot be modeled as quantum tunneling. What. You can use any mathematical model for any process and as long as you correctly account for your assumptions you'll eventually end up with the same answer as the model converges to the physical process, because that's how math works. Not that it's a good idea to do so or an efficient use of time, but intentionally doing math is an activity only slightly saner than making posts on an internet forum. Before this derail goes on further maybe I should point out that the "just barely technically right" line was supposed to indicate a tone of heavy sarcasm and surrealist self-parody when making arbitrary statements that cannot be fully disproved so long as one is willing to continue arguing about dumb poo poo on the internet, but are so overly broad as to be meaningless in any serious discussion. Take the hint bro.
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Oct 25, 2019 20:54
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From a chemistry perspective where we deal mostly with molecules and electrons, quantum forbidden stuff happens all the time because the system is jiggling in and out of symmetry. Phosphorescence is a spin forbidden process for example. I guess at absolute zero it really would never happen.
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Oct 25, 2019 21:12
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Zereth posted:isn't a nucleus ejecting protons called "fission" Really depends on what you want to consider an atom and what you don't. Technically you can consider a lone proton a hydrogen atom with no electron but that's kind of silly since it's just a random proton hanging out all on its own.
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Oct 25, 2019 23:12
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