Tungsten for radiation shielding use • Hacker News Board

Re: Tungsten for radiation shielding use

#61

Post by proto_lambda » Mon, Mar 20, 2023, 1:45 PM UTC

theelous3 wrote: post #52

proto_lambda wrote: post #33

Earlier quoted context omitted.

The first sentence of your comment was structured like this: [reason to use lead], but [reason to use tungsten]. At least I expected the second sentence to expand on the pros of tungsten, when in fact it was about the pros of lead; interpreting it as the former would mean lead is a hard material.

The article explains the beneficial properties of tungsten with rad shielding. Tungsten sheilds better than lead. Lead is easier to form to simple shapes (flats, straight forward wraps). It is essentially impossible to form it in to complex shapes. Tungsten has a high temperature resistance, and low deformation under load. Broadly speaking it can be relied upon to stay in the shape it's machined to. But getting in to…

> Tbh I have no idea how you came away thinking I said lead is hard.

I did not, in fact, come away thinking lead is hard. I did, however, explain and spell out for you how @kragen probably did so; I'm not sure how I can make it any more clear.

Re: Tungsten for radiation shielding use

#62

Post by scythe » Mon, Mar 20, 2023, 3:16 PM UTC

kragen wrote: post #46

scythe wrote: post #17

Earlier quoted context omitted.

If it's only 75% tungsten, I'm figuring it's a tungsten powder. I work with lead all the time but I would not fuck with lead dust. Lead sulfide would be much safer, although studies feeding it to rats did show elevated lead levels. That said, no metal dust is very nice. Solid lead might be safer than tungsten powder. Maybe you could make an iodinated polymer or use a barium cement.

my candidate list of high-density fillers from dernocua (sorry for markdown) is - Osmium: [US$13000/kg][8], 22.65 g/cc, or possibly iridium at more than twice that price - Tungsten: [US$30/kg][9], 19.3 g/cc - Tungsten carbide? Not sure what it costs but its density is 15.6 g/cc. - Lead scrap: 95¢/kg, 11.3 g/cc - Steel scrap: [21¢/kg][10], 7.9 g/cc - Magnetite: [10¢/kg][11] [or so][12], 5.2 g/cc - Quartz (as construct…

Density alone is a weak parameter. For photons with energy below 200 keV — that is, most of them — the attenuation is proportional to Z^2, so barium with atomic number 56 is four times as attenuating as nickel with atomic number 28, and lead with atomic number 82 is about twice as effective as barium — all of this before you account for density.

I've done a bit of searching for materials myself. Barium is mined as barite (BaSO4) or witherite (BaCO3), not baryta (BaO*xH2O, caustic), and USGS lists the price of barite as $180/t, or $0.20/kg.

You also have a K-edge effect, which prompted me to wonder whether you can easily produce barium zirconate from the respective ores, which are both cheap — BaZrO3 (sg ~5.5) is not currently manufactured (Zircon sand was <$1/kg until a COVID-related shortage). But at this point I decided I was overthinking it.

Re: Tungsten for radiation shielding use

#63

Post by kragen » Mon, Mar 20, 2023, 9:32 PM UTC

scythe wrote: post #62

kragen wrote: post #46

Earlier quoted context omitted.

my candidate list of high-density fillers from dernocua (sorry for markdown) is - Osmium: [US$13000/kg][8], 22.65 g/cc, or possibly iridium at more than twice that price - Tungsten: [US$30/kg][9], 19.3 g/cc - Tungsten carbide? Not sure what it costs but its density is 15.6 g/cc. - Lead scrap: 95¢/kg, 11.3 g/cc - Steel scrap: [21¢/kg][10], 7.9 g/cc - Magnetite: [10¢/kg][11] [or so][12], 5.2 g/cc - Quartz (as construct…

Density alone is a weak parameter. For photons with energy below 200 keV — that is, most of them — the attenuation is proportional to Z^2, so barium with atomic number 56 is four times as attenuating as nickel with atomic number 28, and lead with atomic number 82 is about twice as effective as barium — all of this before you account for density. I've done a bit of searching for materials myself. Barium is mined as ba…

baryta is barite, not baria. baria is not just caustic but also toxic and prone to produce dangerous peroxides

i think the price i cited for it is retail, locally

i was interested in density for psychological effects when i made the list

thanks for the tip about barium zirconate; it sounds very promising. how about lead zirconate?

Re: Tungsten for radiation shielding use

#64

Post by kragen » Wed, Mar 22, 2023, 4:51 PM UTC

theelous3 wrote: post #60

kragen wrote: post #57

Earlier quoted context omitted.

i think all the post-manufacturing problems you describe with lead — dimensional instability, thermal creep, plastic deformation, incompatibility with hot high pressure environments, vulnerability to wear — are even worse with this filament maybe an exception is that petg's maximum elastic strain is larger than lead's

Considering lead's modulus of elasticity is essentially zero, yes :) You can drill, tap, and generally rely on this material to stay in the shape it was printed at in maaaaaany more situations than lead. Of course the petg in there is a limiting factor, but even plain petg is an order of magnitude better than lead at retaining its shape under a wide range of loads. You can print gears for lathes in petg! And they las…

https://www.matweb.com/search/DataSheet.aspx?MatGUID=ebd6d2c... says lead's modulus of elasticity is 14 gigapascals and https://www.matweb.com/search/datasheet.aspx?MatGUID=cb9580a... lists one variety of petg as having a modulus of elasticity of 2.2 gigapascals; i think you are confusing your material properties with one another

(at such low filler loadings the tungsten will change the modulus of elasticity very little)

petg does have higher yield stress than pure lead (53 megapascals vs. what https://nickelinstitute.org/media/1771/propertiesofsomemetal... says is 17 megapascals) but there are lead alloys that are in the same range of yield stress, including regular lead-tin solder. but they won't last if you try to make change gears out of them precisely because they're harder than petg

by the same token, though, i think you're going to get a lot of springback and long-term distortion out of petg you aren't going to get with lead

Re: Tungsten for radiation shielding use

#65

Post by kragen » Fri, Mar 24, 2023, 12:09 AM UTC

iancmceachern wrote: post #55

kragen wrote: post #53

Earlier quoted context omitted.

are you saying this filament is nothing more than a meaningless exercise in box-checking bureaucracy that is depressing

No, im saying lead is bad and you can't put it in products anymore. Tungsten is ok

lead metal is safer than tungsten to have in your body

https://pubmed.ncbi.nlm.nih.gov/29300000/

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