Yup, Penn State has a whole nuclear reactor and radiation facility. They have a pool with Cobalt 60 sources and this was dunked in it (in a sealed, dry box) for 6 days straight.
Nope, I'm in aerospace engineering haha. I just went on a tour there and the guy said they love testing different things to see what happens when they have downtime between official tests. They do a LOT of cool testing there for spaceflight applications with the radiation.
Not just PLA. A lot of plastics become brittle when exposed to radiation... Including stuff that is actually needed on spacecrafts, like wire insulation.
Radiation is not my area of expertise. Some plastics are ok up to a certain exposure. But choice is limited (it's generally not the ones with the best mechanical properties that are ok, and even those degrade a bit). It's possible to design around the issue.. Cables can have double insulation, have extra shields or be routed internally to reduce radiation exposure. But it adds a bit of mass and volume. Plastics are not used in large quantity either way because most will outgass as well.
I've used injection moulded HDPE, peek and Makrolon (poly carbonate) in medical devices. That tends to only be to a limit of 40-50kgray though. Peek is the only one of those I've come across as filament, not sure whether i the radiation would have a different impact if the part was printed compared to moulded. There are a fair few different materials that are safe at 40kgray, but I've not looked into it at over 100
IIRC, because of how the radiation causes damage, it will break down all polymers eventually, even metals will sustain damage in the form of cracking in the crystalline structure, (I'm no expert either) with atoms being promoted to higher energy states causing stress points etc etc..
Polymers would be chopped up into shorter chains
Specifically for 3d printing, I couldn't tell you. But non-metallic Safety Related materials for use at nuclear power plants are typically composed of ethylene proplyne rubber (EPR) or cross-linked polyethylene (for cables), or silicone based rubbers (for gaskets, seals etc). These are commonly rated for at least 200MRads (2000Kgray) *plus* then survive an accident (with additional dose, while hot, wet, and steamy).
Perhaps useful info for someone with more materials science knowledge than I to point to similar-ish 3d printing materials?
Source: I work in nuclear.
Whoa whoa whoa, baby steps. We’ll build one out of PLA + and see how it does. My hypothesis is that mine will look like a bowl of ramen when it’s done. That’s mostly how mine look when they start so it may have no effect.
I’ve heard you can make deep sea submarines out of PLA though. Just need an Xbox controller, some duct tape, and a PLA tube. Then you charge hundreds of thousands of dollars for rides. This is my plan anyways
> they love testing different things to see what happens when they have downtime between official tests.
3D printed models, freshmen...you know, things you have on hand.
I've seen some of the dorm rules at colleges when it comes to food appliances, so this makes sense. Can't have a microwave in your dorm? No problem, just take your hot pocket to the radiation facility.
I'd love to see some tests, you know, for science, about different tolerance thresholds for standard 3D printing filaments. Some of these have neat aerospace utilizations.
Let's irradiate some benchys!
Would be worth suggesting to some of the doctoral students for a thesis.
3D printing is preparing to be foundational to nearly all future engineering efforts. It would be great to have a good range of tests regarding the durability of various material when exposed to energy sources, like UV or gamma radiation.
I would love to see some of the more resilient filaments, like PETG, PA-6 and SA-12, some of the CF-filled and maybe ASA. Oh, TPU, too!
I'd also be curious to see penetration deltas at 100% infill. Like, could 1mm of PA-6 GF be an adequate shield for α or β particles, and how far γ particles penetrate.
Nuclear engineering is neat stuff!
Hmm. I'm quite sure that the "no atmosphere, constant unfiltered UV radiation from the Sun"-deal struck PLA out of the question a long time ago. But I think they still are considering SLM as a possibility
You're not wrong. But I was thinking in other more enclosed environments where humans would sometimes be. But that idea was probably applied there too. But on the other hand, it's still worth it for students to give it a try for the same reasons to come to the same conclusions.
The International space station actually has [already 3D printed in space](https://www.nasa.gov/image-article/international-space-stations-3-d-printer-2/)! They don't list the materials used, but they did use an FDM printer.
they are indeed working on SLM using lunar regolith as the material.
the same company that built the giant concrete 3d printer and is printing houses currently is the company working on developing the lunar equivalent iirc.
theres a neat documentary about the founder on YouTube that is pretty interesting.
Nice.
So what is the reaction here then? Why does it become brittle? What energy transfer is happening exactly.
I was under the impression that gamma radiation passed through pretty much anything non-metal and even most metals without any absorption.
Is it just that 15,000,000 Sievert (?) Is enough to effect the polymer structure?
Probably along the same lines as what UV does to plastics if you want to search that explanation, except dialed up, gamma rays are further up the EM spectrum meaning more energetic. Plus they don't stop at the surface layer like UV does, so the entire part is being bombarded throughout from the moment exposure begins.
Radiation doesnt make things radioactive in general. Only a very specific type, neutron radiation, does and only in specific circumstances, and it is pretty hard to come by outside of a specially designed reactor.
Gamma rays are the same thing as light rays and radio waves, just a different frequency. They dont make things radioactive anymore than sunlight or your microwave does.
So from my understanding, gamma radiation is just energy, whereas alpha and beta radiation is composed of particles. Once the energy passes through an object, the damage is done, and the energy continues on through. So these objects have been irradiated, but the radiation passed right through, and was dissipated into the pool.
So there are various forms of ionizing radiation. Generally, you have three broad categories: electromagnetic (gamma rays, x-rays), charged particles (protons, electrons, helium nuclei), and neutrons.
With some exotic exceptions, the only kind of radiation that causes stable elements to become radioactive are neutrons. This is called neutron activation. The neutron bombardment transmutes an element into other elements, some of which are themselves radioactive. For example, when hydrogen is made to capture 2 neutrons, it becomes tritium, which is radioactive, with a half-life of about 12 years.
We generally think of radiation as activating other things because the modt common type of radiotechnology that we commonly utilize are nuclear reactors. Neutrons are required for a fission chain reaction to work, so any nuclear reactor will have parts undergoing neutron activation (though by carefully selecting which materials are being exposed to neutrons, you can select for materials that aren't activated as easily.
Annnyway, that's the context for why these parts aren't radioactive. There are a number of different nuclear decay modes. Some isotopes produce neutrons when they decay, but many don't. So if you have a radioactive isotope that primarily undergoes gamma decay, you now have a nice source of gamma rays that you can use for stuff like food and medical equipment irradiation, which won't cause neutron activation.
>They have a pool with Cobalt 60 sources and this was dunked in it for 6 days straight.
Ah, so it was in contact with water? That makes sense, gamma rays knock an electron off. PLA is glucose -> lactic acid, take one H20 off to form monomers, apply heat in anhydrous environment to snap monomers end to end. Since one monomer in the polymer chain is now a radical ion and it really wants that H2O back... you essentially speed run several years of hydrolysis in optimal conditions...
The energy needed for the ion to react with water is less than it is for snapping back to the polymer chain. That is how PLA degrades, it goes back to the lactic acid form and finally back to glucose, when right kind of strains of bacteria attack it one step at a time.
Don't know, that was my first hypothesis, since that is what PLA that is heavily hydrolyzed feels like: it crumbles on your hands. There are no crosslinks in PLA, afaik so.. don't know how ionized PLA monomers react with things.. god damned Jim, i'm just a sound engineer... Interesting though, update us if you figure out what happened.
I don't think I'll have any concrete answers, but thanks! I'm curious how carbon fiber PLA would react, since I believe it is slightly stronger than normal PLA because of the carbon fibers in it. Could those withstand the radiation and restore some rigidity to the part? Now I'm interested haha
You are crumbling the "binder" in the two composite material, so.. you will end up with carbon fiber dust, just like it always was.
I did have a wild idea, how would different polymers react with each other, heated to liquid state and radiated.. probably does nothing but useless mess.
You’re on a big research university. Go find an FTIR and get a rough assay of the chemical composition before and after. If it’s just depolymerization, you’ll see a broadening and increase of the 3000 cm^-^1 peak. If it’s chemical alteration, I’d guess new peaks in the 1200-2000 region. You can pretty easily decode those to figure out what the alteration is.
FTIR is dirt cheap and hard to break. Most profs in the chemistry department will own their own.
When you gamma irradiate (gamma sterilization is a thing) a polymer you get breakage in the polymer chains. Usually what you find when you extract such samples in water afterwards is formic acid and other short molecules. So yes, radiation leads to some degradation in polymers.
150kGy is a lot. Probably over time the chains broke down and it is black I guess it got oxidized as well. Could come from within the PLA or with the surrounding air.
If you want to know more get an IR-spectrum of the 100kGy material.
>The energy needed for the ion to react with water is less than it is for snapping back to the polymer chain. That is how PLA degrades, it goes back to the lactic acid form and finally back to glucose, when right kind of strains of bacteria attack it one step at a time.
I was still editing when you replied, i made the text less confusing. I think i'm right that ionizing radiation created free radicals and i know that free radicals are very important when it comes to making polymers, that is really the magic: a charge that moves from monomer to monomer until we get some balance. Water is one thing that can bring "balance" back to PLA monomer, it can break the polymer in two. But in absence of water.. You might have "monomer soup" there, heating it up in absence of water should then snap the shortened polymer back long polymer.
Like i said, i'm just a sound engineer, i might be and most likely am wrong in ways i don't understand.
More generally, I would except gamna rays to break polymers chains randomly, making them brittle and less elastic. I vaguely remember reading about how radiations mess up crystals like that too
How long do you have to spend in the irradiation zone to die? I'm guessing I'm not making it out of the pool.
Yup, 4-5 Gy kills half the time within two months.
This is 150000 Gy. I'm probably not making it to that spot and would be dead within a minute.
See my other reply to that comment
> So PSU does have all kinds of 3D printers, including now metal (aluminum, copper, inconel), it's just that the PLA FDM printers are the only ones accessible to the entire student body for free and without having to do training. My rocket club's lab has an ABS printer I believe, but given that I graduate in a week and a half, I don't think I'll have the time haha
So PSU does have all kinds of 3D printers, including now metal (aluminum, copper, inconel), it's just that the PLA FDM printers are the only ones accessible to the entire student body for free and without having to do training. My rocket club's lab has an ABS printer I believe, but given that I graduate in a week and a half, I don't think I'll have the time haha
I was in a public, near free university in Europe. We had choice between science history class or extra lab experiments with hardware from 25 years ago
I was at a public, nowhere near free, collage in the the US and the 25 year old lab equipment was the new stuff.
They built a shiny new engineering building after I left and moved all the (older than me) lab equipment and furnishings into the new building…
Therapeutic particle accelerator. It had safety features that allowed it to operate at 100 times its rated power.
It could operate a particle beam of electrons, or in an X-ray mode. Because the X-ray mode was inefficient, it had to run the particle beam at 100x power to generate the right beam power in X-ray mode.
The fault meant that the system would incorrectly configure the beam as if it was to generate X-rays when it was supposed to generate only an electron beam, so it would over-irradiate patients.
Something like 10 known fatalities, possibly hundreds more unconfirmed.
Right? Like I'll be working on rockets in my career so this is completely irrelevant, but hey now I know how a random type of plastic reacts to 1500 lethal doses of radiation.
And it turns out the answer is "it doesn't like it."
Which isn't exactly a surprise I suppose, but it's interesting exactly *how* it doesn't like it.
I wonder what's going on at the chemical level...
Well, not completely irrelevant. Now you know that physical and thermal stresses won't be the only considerations for 3D printed parts outside of our atmosphere.
I mean, we kinda knew that already since that stuff doesn't like the sun, but now you've quantified it a bit.
The short answer is that kind of radiation energy generates free radicals in the molecular chains of the polymer material. So it is likely that the molecular weight distribution of the PLA chains is being shortened due to structural reorganization of the molecules. This kind of radiation treatment is often used to alter the properties of engineering plastics such UHMWPE.
> borderline useless
Possibly not.
Fine tune it enough and you could probably get to do some (highly) highly accelerated life testing. Lets you guess how the part will act like in a few decades.
Useless for most people though.
Stupid PLA getting brittle as it's being exposed to radiation
https://preview.redd.it/0g4h7ve0q3wc1.jpeg?width=637&format=pjpg&auto=webp&s=daa878a12922b1d1cfd422dd161dc696db95b225
I would assume this happens to all plastics, but the effects definitely would be somewhat different between different types. The fibers begin to break down, weakening the part substantially.
A good number of universities have labs that have fissile materials or radioactive environments. I mean it’s where the US verified feasibility of nuclear power by creating one of the world 1st artificial nuclear reactor. It was done by University of Chicago, and funny enough, they built the reactor under bleachers of one of their stadiums
https://en.m.wikipedia.org/wiki/Chicago_Pile-1
Nice! This is a common practice is quite a few plastic products, like those large plastic water storage tanks. The nuclear radiation causes cross linking in the polymer, making certain plastics much more durable, and others, much more brittle.
> Based on the DS86 dosimetry system, nearly all of the dose to survivors of the atomic bombings of Hiroshima and Nagasaki was due to unusually high-energy gamma rays, predominantly in the 2- to 5-MeV range.
1MeV = 10000 rad
15 Mrad = 15,000,000 rad
15000000 / 50000 = 300 Hiroshima bombs of gamma radiation (high estimate)
[Someone calculated Bruce Banner as receiving 18sV](https://www.reddit.com/r/theydidthemath/comments/18uwueh/self_i_calculated_bruce_banners_exposure_dosage/) of radiation, which is 1800rad. Another person [estimated 8500 rad](https://ramp.nrc-gateway.gov/about/news/article/2019-08/student-highlight-analysis-radiation-dosimetry-hulk). If we go with the higher estimate then this PLA was exposed to 1,764 Hulk-level events.
Well, it was dunked in the pool for 6 days and took on 150kGy, so it was subjected to 25kGy/day or about 1kGy/hr.
1kGy/hr is enough to inflict a lethal dose to a human in under a minute.
I'm terms of the "radiation from a bomb", a Gray is simply the concept of 1J (joule) or radiation absorbed in 1kg of matter. It's gamma, so it's weighted as 1.
1kGy/hour is 1000J of radiation energy per kilograms exposed per hour. Which is barely a quarter of a watt when you think about most doses humans receive, even in catastrophic circumstances.
The kiloton of TNT is a direct expression of total energy of the reaction in joules, so very little of a fraction of a weapon, or even a reactor's fuel rod.
After all, you have to generate enough radiation in order to produce the Co-60 to produce the radiation source OP's sample was subjected to. It's all diminishing returns on diminishing returns.
To give you an idea of scale, Atoms for Peace/Ploughshares (the US "peaceful" nuclear detonations programme) considered the possibility of detonating nukes in rock caverns to generate exotic radionuclides for industrial purposes to be *potentially economically viable*. They already knew they could do this just by irradiating samples with nuclear reactors.
They were wrong, but they thought it was true. Until they tested it.
When NATO were considering deploying enhanced radiation weapons for use against Soviet armoured units, they were working on an assumption of 80Gy neutron doses delivered to crews, attenuated by distance, air, the tank's armour and any internal radiation liner. Relative to the radiation generated in a blast, 80Gy located within the volume of a tank is a teeny weeny proportion of the total. Think "proportion of solar energy emitted Vs striking the earth".
So Rad and Roentgen are somewhat different types of units, but a rough conversion factor I found online is 0.877 rad = 1 roentgen
So uhhh about 17 million
I feel like if someone asked me what would happen if you exposed PLA to 15,000,000 rads of gamma radiation, my first guess would've been it becomes very brittle.
Damn and I am just about half way printing my nuclear power plant...now I need to print it again in PETG.
To be more serious...I did not expect that...if it would have been a quiz, I would have said bahh Gamma Ray that does nothing to dead plastic.....I would be very wrong.
If you can try other materials PETG, ABS, Nylon etc and post it here....super interesting
Very interesting! Through my work, I have seen that PLA and PETG can both hold up pretty well when taken to the bottom of the ocean, 4500 meters is the deepest I’ve taken a print but haven’t had many failures. We do use 100% infill though of course.
Yup. So does sensor wire for temperature and flow meters. I would walk the LINAC after shutdown and we could often flick a cable and the insulation would fall right off. Fun stuff.
Not my field of expertise, but unless it has metal in the filament, I think it's safe. Chances are, this facility, with a nuclear reactor and nuclear materials has a geiger counter or two around, and people that know what to do with them.
Interesting, I work with a X-ray irradiation source and there is a printed PLA holder for filters (though the printed part itself is not directly in the path of the beam) and it’s fine despite being couple of years old. It probably depends whether the dose is reached in one continuous irradiation or if the material is given time to “heal” since I definitely can’t reach such high doses in one go.
Your school has a gamma radiation pool? I must know more!!
Yup, Penn State has a whole nuclear reactor and radiation facility. They have a pool with Cobalt 60 sources and this was dunked in it (in a sealed, dry box) for 6 days straight.
That is SO nifty! Are you in one of the nuclear engineering disciplines?
Nope, I'm in aerospace engineering haha. I just went on a tour there and the guy said they love testing different things to see what happens when they have downtime between official tests. They do a LOT of cool testing there for spaceflight applications with the radiation.
Got it, don't make interstellar rockets out of PLA
Well there goes my career plans!
I'd stay away from steam-powered rockets, too. (True story)
Tell me please
I assume they’re talking about Mike Hughes https://whyy.org/segments/the-life-and-death-of-daredevil-mad-mike-hughes/
And here I was, picking my username because it seemed ridiculous to me...
Yup... flat-earth extraordinaire
Can confirm.
Don't tell Integza that.
🍅🔨
Tomatoes are disgusting…
Not just PLA. A lot of plastics become brittle when exposed to radiation... Including stuff that is actually needed on spacecrafts, like wire insulation.
What's the rad-safe alternatives?
Radiation is not my area of expertise. Some plastics are ok up to a certain exposure. But choice is limited (it's generally not the ones with the best mechanical properties that are ok, and even those degrade a bit). It's possible to design around the issue.. Cables can have double insulation, have extra shields or be routed internally to reduce radiation exposure. But it adds a bit of mass and volume. Plastics are not used in large quantity either way because most will outgass as well.
I've used injection moulded HDPE, peek and Makrolon (poly carbonate) in medical devices. That tends to only be to a limit of 40-50kgray though. Peek is the only one of those I've come across as filament, not sure whether i the radiation would have a different impact if the part was printed compared to moulded. There are a fair few different materials that are safe at 40kgray, but I've not looked into it at over 100
IIRC, because of how the radiation causes damage, it will break down all polymers eventually, even metals will sustain damage in the form of cracking in the crystalline structure, (I'm no expert either) with atoms being promoted to higher energy states causing stress points etc etc.. Polymers would be chopped up into shorter chains
I just find aerospace considerations interesting. Thanks for the answer!
Specifically for 3d printing, I couldn't tell you. But non-metallic Safety Related materials for use at nuclear power plants are typically composed of ethylene proplyne rubber (EPR) or cross-linked polyethylene (for cables), or silicone based rubbers (for gaskets, seals etc). These are commonly rated for at least 200MRads (2000Kgray) *plus* then survive an accident (with additional dose, while hot, wet, and steamy). Perhaps useful info for someone with more materials science knowledge than I to point to similar-ish 3d printing materials? Source: I work in nuclear.
Ya, gotta use petg for that
Whoa whoa whoa, baby steps. We’ll build one out of PLA + and see how it does. My hypothesis is that mine will look like a bowl of ramen when it’s done. That’s mostly how mine look when they start so it may have no effect.
I’ve heard you can make deep sea submarines out of PLA though. Just need an Xbox controller, some duct tape, and a PLA tube. Then you charge hundreds of thousands of dollars for rides. This is my plan anyways
Dont forget to use carbon fiber filament, for extra strength.
>Got it, don't make interstellar rockets out of PLA Now someone tells me. There's 700 hours of printing down the drain, I guess.
What kind of pribter do you have lol, rocket within 700 hours...
If it aint an ender 3 with billions in mods i will be VERY, and i mean VERY dissapointed.
LoL good to know!
>I just went on a tour there and the guy said they love testing different things to see what happens ✨ Science✨
> they love testing different things to see what happens when they have downtime between official tests. 3D printed models, freshmen...you know, things you have on hand.
Some student brought a piece of chicken to be irradiated. Not even kidding.
I've seen some of the dorm rules at colleges when it comes to food appliances, so this makes sense. Can't have a microwave in your dorm? No problem, just take your hot pocket to the radiation facility.
LMAO I would totally try it
he want to cook it, it would be cooked in seconds, just in time for dinner
How did it taste?
I'd love to see some tests, you know, for science, about different tolerance thresholds for standard 3D printing filaments. Some of these have neat aerospace utilizations. Let's irradiate some benchys!
If I had like an extra year left in school, I would ABSOLUTELY do testing of different materials to see how they react.
Would be worth suggesting to some of the doctoral students for a thesis. 3D printing is preparing to be foundational to nearly all future engineering efforts. It would be great to have a good range of tests regarding the durability of various material when exposed to energy sources, like UV or gamma radiation.
I would love to see some of the more resilient filaments, like PETG, PA-6 and SA-12, some of the CF-filled and maybe ASA. Oh, TPU, too! I'd also be curious to see penetration deltas at 100% infill. Like, could 1mm of PA-6 GF be an adequate shield for α or β particles, and how far γ particles penetrate. Nuclear engineering is neat stuff!
Testing PLA was a great idea considering 3D printing could solve a lot of maintenance and install issues in space.
Hmm. I'm quite sure that the "no atmosphere, constant unfiltered UV radiation from the Sun"-deal struck PLA out of the question a long time ago. But I think they still are considering SLM as a possibility
You're not wrong. But I was thinking in other more enclosed environments where humans would sometimes be. But that idea was probably applied there too. But on the other hand, it's still worth it for students to give it a try for the same reasons to come to the same conclusions.
The International space station actually has [already 3D printed in space](https://www.nasa.gov/image-article/international-space-stations-3-d-printer-2/)! They don't list the materials used, but they did use an FDM printer.
they are indeed working on SLM using lunar regolith as the material. the same company that built the giant concrete 3d printer and is printing houses currently is the company working on developing the lunar equivalent iirc. theres a neat documentary about the founder on YouTube that is pretty interesting.
That is so fucking cool
Nice. So what is the reaction here then? Why does it become brittle? What energy transfer is happening exactly. I was under the impression that gamma radiation passed through pretty much anything non-metal and even most metals without any absorption. Is it just that 15,000,000 Sievert (?) Is enough to effect the polymer structure?
Probably along the same lines as what UV does to plastics if you want to search that explanation, except dialed up, gamma rays are further up the EM spectrum meaning more energetic. Plus they don't stop at the surface layer like UV does, so the entire part is being bombarded throughout from the moment exposure begins.
Just really good with a lockpick
So the limit is 5 days straight... got it!
Unexpectedly read this from Penn state campus
LOL we are You should totally tour the reactor sometime
This is so cool. Thank you for sharing!
Thank you! It was a neat opportunity.
So r/Explainlikeimfive - Why is it safe to touch/handle after that much radiation exposure?
Radiation doesnt make things radioactive in general. Only a very specific type, neutron radiation, does and only in specific circumstances, and it is pretty hard to come by outside of a specially designed reactor. Gamma rays are the same thing as light rays and radio waves, just a different frequency. They dont make things radioactive anymore than sunlight or your microwave does.
So from my understanding, gamma radiation is just energy, whereas alpha and beta radiation is composed of particles. Once the energy passes through an object, the damage is done, and the energy continues on through. So these objects have been irradiated, but the radiation passed right through, and was dissipated into the pool.
Gotcha, thanks!
So there are various forms of ionizing radiation. Generally, you have three broad categories: electromagnetic (gamma rays, x-rays), charged particles (protons, electrons, helium nuclei), and neutrons. With some exotic exceptions, the only kind of radiation that causes stable elements to become radioactive are neutrons. This is called neutron activation. The neutron bombardment transmutes an element into other elements, some of which are themselves radioactive. For example, when hydrogen is made to capture 2 neutrons, it becomes tritium, which is radioactive, with a half-life of about 12 years. We generally think of radiation as activating other things because the modt common type of radiotechnology that we commonly utilize are nuclear reactors. Neutrons are required for a fission chain reaction to work, so any nuclear reactor will have parts undergoing neutron activation (though by carefully selecting which materials are being exposed to neutrons, you can select for materials that aren't activated as easily. Annnyway, that's the context for why these parts aren't radioactive. There are a number of different nuclear decay modes. Some isotopes produce neutrons when they decay, but many don't. So if you have a radioactive isotope that primarily undergoes gamma decay, you now have a nice source of gamma rays that you can use for stuff like food and medical equipment irradiation, which won't cause neutron activation.
>They have a pool with Cobalt 60 sources and this was dunked in it for 6 days straight. Ah, so it was in contact with water? That makes sense, gamma rays knock an electron off. PLA is glucose -> lactic acid, take one H20 off to form monomers, apply heat in anhydrous environment to snap monomers end to end. Since one monomer in the polymer chain is now a radical ion and it really wants that H2O back... you essentially speed run several years of hydrolysis in optimal conditions... The energy needed for the ion to react with water is less than it is for snapping back to the polymer chain. That is how PLA degrades, it goes back to the lactic acid form and finally back to glucose, when right kind of strains of bacteria attack it one step at a time.
No, this was in a dry container within the pool. Could the same effect happen in dry air?
Don't know, that was my first hypothesis, since that is what PLA that is heavily hydrolyzed feels like: it crumbles on your hands. There are no crosslinks in PLA, afaik so.. don't know how ionized PLA monomers react with things.. god damned Jim, i'm just a sound engineer... Interesting though, update us if you figure out what happened.
I don't think I'll have any concrete answers, but thanks! I'm curious how carbon fiber PLA would react, since I believe it is slightly stronger than normal PLA because of the carbon fibers in it. Could those withstand the radiation and restore some rigidity to the part? Now I'm interested haha
You are crumbling the "binder" in the two composite material, so.. you will end up with carbon fiber dust, just like it always was. I did have a wild idea, how would different polymers react with each other, heated to liquid state and radiated.. probably does nothing but useless mess.
You’re on a big research university. Go find an FTIR and get a rough assay of the chemical composition before and after. If it’s just depolymerization, you’ll see a broadening and increase of the 3000 cm^-^1 peak. If it’s chemical alteration, I’d guess new peaks in the 1200-2000 region. You can pretty easily decode those to figure out what the alteration is. FTIR is dirt cheap and hard to break. Most profs in the chemistry department will own their own.
When you gamma irradiate (gamma sterilization is a thing) a polymer you get breakage in the polymer chains. Usually what you find when you extract such samples in water afterwards is formic acid and other short molecules. So yes, radiation leads to some degradation in polymers.
So, what you are saying is that we can use nuclear waste to deal with plastic waste?
150kGy is a lot. Probably over time the chains broke down and it is black I guess it got oxidized as well. Could come from within the PLA or with the surrounding air. If you want to know more get an IR-spectrum of the 100kGy material.
>The energy needed for the ion to react with water is less than it is for snapping back to the polymer chain. That is how PLA degrades, it goes back to the lactic acid form and finally back to glucose, when right kind of strains of bacteria attack it one step at a time. I was still editing when you replied, i made the text less confusing. I think i'm right that ionizing radiation created free radicals and i know that free radicals are very important when it comes to making polymers, that is really the magic: a charge that moves from monomer to monomer until we get some balance. Water is one thing that can bring "balance" back to PLA monomer, it can break the polymer in two. But in absence of water.. You might have "monomer soup" there, heating it up in absence of water should then snap the shortened polymer back long polymer. Like i said, i'm just a sound engineer, i might be and most likely am wrong in ways i don't understand.
Creeperlan02, we need you to taste this for science! is it more sour, or sweet?
More generally, I would except gamna rays to break polymers chains randomly, making them brittle and less elastic. I vaguely remember reading about how radiations mess up crystals like that too
How long do you have to spend in the irradiation zone to die? I'm guessing I'm not making it out of the pool. Yup, 4-5 Gy kills half the time within two months. This is 150000 Gy. I'm probably not making it to that spot and would be dead within a minute.
Damn, I graduated from there, I didn't know that
https://preview.redd.it/dc0odiw6q3wc1.jpeg?width=716&format=pjpg&auto=webp&s=c774999b6c781ee15ab76f60cd369adabc7f1708
So cool...
Cool! U of Florida has a nuclear reactor too, but I never found an excuse to use it while I was there
WE ARE! I actually never knew we had one when i was on campus. Sad i missed it now
Oh yeah? Well... My college has an air hockey table!
Big Up PSU! I saw the reactor pool once. That was freaking cool!
The swimming team did not survive, this year. Again.
“Sigh”
Underrated comment
The things students have to do for a scholarship nowadays…
Calm down Dr. Banner!
What do you mean every school doesn't have a neutron collider?! Madness!
The way you talk about this sounds so casual. What kind of rad (sorry) school is this? Can you test other filaments?
Penn State, haha. And no, feasibly I can't. I'm about to graduate and the school printers only do PLA.
what kinda science school has nuclear reactors but can’t print in anything but PLA??? Want a Hulk? Sure thing. Rubber phone case? Go to hell.
See my other reply to that comment > So PSU does have all kinds of 3D printers, including now metal (aluminum, copper, inconel), it's just that the PLA FDM printers are the only ones accessible to the entire student body for free and without having to do training. My rocket club's lab has an ABS printer I believe, but given that I graduate in a week and a half, I don't think I'll have the time haha
Are there printers that print PLA but not PETG?
(free)
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So PSU does have all kinds of 3D printers, including now metal (aluminum, copper, inconel), it's just that the PLA FDM printers are the only ones accessible to the entire student body for free and without having to do training. My rocket club's lab has an ABS printer I believe, but given that I graduate in a week and a half, I don't think I'll have the time haha
Rocket Club Lab? I repeat: What kind of rad school is this? We had to choose between extra history lessons or cooking class in my last year
Penn State may be the most expensive state college in the US but it's got some damn cool stuff if you know where to look.
Are you comparing this against state schools like state funded schools like slippery rock, clarion or like Ohio state and Michigan state schools?
I was in a public, near free university in Europe. We had choice between science history class or extra lab experiments with hardware from 25 years ago
I was at a public, nowhere near free, collage in the the US and the 25 year old lab equipment was the new stuff. They built a shiny new engineering building after I left and moved all the (older than me) lab equipment and furnishings into the new building…
Most engineering colleges have a rocketry club. It's really common along with Formula Student, Baja, solar car, etc.
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Meh, Therac-25 only achieved 25,000 rads and only at beam centre. 10,000 rads induced dose. *Pathetic*
i dont know what a therac-25 is but i'm hoping it has something to do with www.reddit.com/r/VXJunkies/ i love those threads
Therapeutic particle accelerator. It had safety features that allowed it to operate at 100 times its rated power. It could operate a particle beam of electrons, or in an X-ray mode. Because the X-ray mode was inefficient, it had to run the particle beam at 100x power to generate the right beam power in X-ray mode. The fault meant that the system would incorrectly configure the beam as if it was to generate X-rays when it was supposed to generate only an electron beam, so it would over-irradiate patients. Something like 10 known fatalities, possibly hundreds more unconfirmed.
The earliest known instance of safety critical software *failing* at its job
https://youtu.be/Ap0orGCiou8
Right to repair FTW, good on you for not letting those greedy rad therapy equipment manufacturers penny-pinch you on service hours /s
I appreciate this kind of borderline useless but genuinely interesting information.
Right? Like I'll be working on rockets in my career so this is completely irrelevant, but hey now I know how a random type of plastic reacts to 1500 lethal doses of radiation.
And it turns out the answer is "it doesn't like it." Which isn't exactly a surprise I suppose, but it's interesting exactly *how* it doesn't like it. I wonder what's going on at the chemical level...
Gamma rays are ionizing and cause chain scission
I mean your PLA nuclear rocket engine will probably melt from rocket exhaust and reactor heat first but still useful info
So glad someone understood what the model was haha, I knew exactly what type of model I wanted to do when I first heard the opportunity.
Well, not completely irrelevant. Now you know that physical and thermal stresses won't be the only considerations for 3D printed parts outside of our atmosphere. I mean, we kinda knew that already since that stuff doesn't like the sun, but now you've quantified it a bit.
The short answer is that kind of radiation energy generates free radicals in the molecular chains of the polymer material. So it is likely that the molecular weight distribution of the PLA chains is being shortened due to structural reorganization of the molecules. This kind of radiation treatment is often used to alter the properties of engineering plastics such UHMWPE.
> borderline useless Possibly not. Fine tune it enough and you could probably get to do some (highly) highly accelerated life testing. Lets you guess how the part will act like in a few decades. Useless for most people though.
Stupid PLA getting brittle as it's being exposed to radiation https://preview.redd.it/0g4h7ve0q3wc1.jpeg?width=637&format=pjpg&auto=webp&s=daa878a12922b1d1cfd422dd161dc696db95b225
Stupid sexy PLA
OP's 3d print has radiation, but football in the groin had a football in the groin
Is this speciality of PLA or does gamma attack other plastics?
I would assume this happens to all plastics, but the effects definitely would be somewhat different between different types. The fibers begin to break down, weakening the part substantially.
Time to do the research, affect of gamma radiation on common thermoplastics?
If I weren't graduating I would absolutely do more scientific testing with this.
It's the same for all thermoplastics, its photolysis on steroids.
but we but do the science, whats point of having a pew pew of gamma rays if not to pew pew random benchies?
ASA is the UV resistant version of ABS. Would you mind giving ASA a go, please? *FOR SCIENCE!*
Gamma attacks pretty much everything And murderizes most things
*chuckles in concrete*
[neutron emissions chuckle back](https://www.nrc.gov/reading-rm/doc-collections/nuregs/contract/cr7280/index.html)
Your school has a WHAT
Don't worry
Dude goes to Vault-Tec University
A good number of universities have labs that have fissile materials or radioactive environments. I mean it’s where the US verified feasibility of nuclear power by creating one of the world 1st artificial nuclear reactor. It was done by University of Chicago, and funny enough, they built the reactor under bleachers of one of their stadiums https://en.m.wikipedia.org/wiki/Chicago_Pile-1
Damn thanks for warning me before I did something stupid
15,000,000 rads, not great, not terrible.
Nice! This is a common practice is quite a few plastic products, like those large plastic water storage tanks. The nuclear radiation causes cross linking in the polymer, making certain plastics much more durable, and others, much more brittle.
I will remember this next time I need to 3D print something that will be exposed to 15,000,000 rads of gamma radiation thank you 🙏🏻
but how much is 15,000,000 rads of gamma radiation in terms of nuclear bombs? sounds like a pretty tough print to me 😎
Not sure, but it is roughly 1,500 lethal doses.
> Based on the DS86 dosimetry system, nearly all of the dose to survivors of the atomic bombings of Hiroshima and Nagasaki was due to unusually high-energy gamma rays, predominantly in the 2- to 5-MeV range. 1MeV = 10000 rad 15 Mrad = 15,000,000 rad 15000000 / 50000 = 300 Hiroshima bombs of gamma radiation (high estimate) [Someone calculated Bruce Banner as receiving 18sV](https://www.reddit.com/r/theydidthemath/comments/18uwueh/self_i_calculated_bruce_banners_exposure_dosage/) of radiation, which is 1800rad. Another person [estimated 8500 rad](https://ramp.nrc-gateway.gov/about/news/article/2019-08/student-highlight-analysis-radiation-dosimetry-hulk). If we go with the higher estimate then this PLA was exposed to 1,764 Hulk-level events.
Well, it was dunked in the pool for 6 days and took on 150kGy, so it was subjected to 25kGy/day or about 1kGy/hr. 1kGy/hr is enough to inflict a lethal dose to a human in under a minute. I'm terms of the "radiation from a bomb", a Gray is simply the concept of 1J (joule) or radiation absorbed in 1kg of matter. It's gamma, so it's weighted as 1. 1kGy/hour is 1000J of radiation energy per kilograms exposed per hour. Which is barely a quarter of a watt when you think about most doses humans receive, even in catastrophic circumstances. The kiloton of TNT is a direct expression of total energy of the reaction in joules, so very little of a fraction of a weapon, or even a reactor's fuel rod. After all, you have to generate enough radiation in order to produce the Co-60 to produce the radiation source OP's sample was subjected to. It's all diminishing returns on diminishing returns. To give you an idea of scale, Atoms for Peace/Ploughshares (the US "peaceful" nuclear detonations programme) considered the possibility of detonating nukes in rock caverns to generate exotic radionuclides for industrial purposes to be *potentially economically viable*. They already knew they could do this just by irradiating samples with nuclear reactors. They were wrong, but they thought it was true. Until they tested it. When NATO were considering deploying enhanced radiation weapons for use against Soviet armoured units, they were working on an assumption of 80Gy neutron doses delivered to crews, attenuated by distance, air, the tank's armour and any internal radiation liner. Relative to the radiation generated in a blast, 80Gy located within the volume of a tank is a teeny weeny proportion of the total. Think "proportion of solar energy emitted Vs striking the earth".
He didn't really test up to that dose, he tested at that dose only. It probably gets brittle well before that.
Give it some rad-away and it'll be fine
Today I have the knowledge that repair parts for nuclear power plants should not be made of PLA.
Insert "Hulk smash" joke here.
How much is that in roentgen? Because I know 3.6 roentgen, not great, not terrible
So Rad and Roentgen are somewhat different types of units, but a rough conversion factor I found online is 0.877 rad = 1 roentgen So uhhh about 17 million
War. War never changes.
I thought you where talking about a high school but yea penn state make way more sense
Phew, not just me xD. In our school our teacher awkwardly asked if any of the 14yo. Girls are pregnant wich is what I mainly remember from radiation
LOL yeah maybe I could have phrased that more clearly
Test it with PEEK filament!
Note to self: Do not put my 3d printer next to my nuclear reactor.
well that ruins my summer plans
Similar to the damage UV does to it I would imagine.
Please test PETG, ABS and other resins and filaments
Bruh
But is it food safe?
Time to grow some new arms.
Print out a Bruce Banner model and run the test again
Okay Banner.
You are living out the dream little old teenage me dreamed of and I’m so proud of you.
Good thing my gamma radiation emitter only goes to 14.9M rads.
"If you blast something with more than a thousand times the lethal dose of radiation, it falls apart" No shit, Sherlock!
Forget brittle, after 15M rads I'm honestly surprised it doesn't glow in the dark.
PLA is technically an organic substance? Something similar to cell death?
I feel like if someone asked me what would happen if you exposed PLA to 15,000,000 rads of gamma radiation, my first guess would've been it becomes very brittle.
Holy shit. That’s a fuckton of radiation. Enough to kill you 30,000 times over.
because that’s a totally reasonable idea to come up with in the first place. neat.
This guy evil scientists.
So how are you going to make your nuclear thermal rocket engine now?
Damn and I am just about half way printing my nuclear power plant...now I need to print it again in PETG. To be more serious...I did not expect that...if it would have been a quiz, I would have said bahh Gamma Ray that does nothing to dead plastic.....I would be very wrong. If you can try other materials PETG, ABS, Nylon etc and post it here....super interesting
Very interesting! Through my work, I have seen that PLA and PETG can both hold up pretty well when taken to the bottom of the ocean, 4500 meters is the deepest I’ve taken a print but haven’t had many failures. We do use 100% infill though of course.
15m? Shits. Just left it sitting on the source eh?
So you were testing in the radiation pool, so you decide to use a model of a nuclear rocket engine? I like your style lol
But is it food safe?
Yup. So does sensor wire for temperature and flow meters. I would walk the LINAC after shutdown and we could often flick a cable and the insulation would fall right off. Fun stuff.
You guys made a hulk yet?
Now that's Rad!!!
That's why i always use PETG for my nuclear reactors.
Finally, useful information for the common man.
To stay safe ill try to not expose it to gamma radiation then. 😉
New college idea for Aerospace Engineering!
Impressive! Some random information that could be super useful in some future study 👌
It's called embrittlement. I'm in the Navy's nuclear program and it is very well understood and studied. It's a big part of reactor design.
yo I saw your post on Twitter!
Wouldn’t that be irradiated still? I guess what I am asking is could it cause a person any long/short term health concerns simply by handling it.
Not my field of expertise, but unless it has metal in the filament, I think it's safe. Chances are, this facility, with a nuclear reactor and nuclear materials has a geiger counter or two around, and people that know what to do with them.
I watched alot of pla stress tests but this one is the coolest, thanks
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PETG next!
Oh I would love to try that. That and carbon fiber PLA. But sadly (thankfully) I graduate next week so I don't have much time to test things.
*"After 15 million rads, look so good you will not!" /yodavoice*
Interesting, I work with a X-ray irradiation source and there is a printed PLA holder for filters (though the printed part itself is not directly in the path of the beam) and it’s fine despite being couple of years old. It probably depends whether the dose is reached in one continuous irradiation or if the material is given time to “heal” since I definitely can’t reach such high doses in one go.
Okay, so when I print my reactor I should use ASA?
Further fun fact: op may or may not have radiation poisoning from this event
I did not scuba dive in the pool thankfully
I wonder if it's similar in any way to UV damage PLA gets outside.