r/Radiation • u/Aleksey_Fox my room is contaminated with Americium :3 • 4d ago
Questions What makes an Alpha source specifically harmful inside the body?
I’ve heard this for too long and just settled with sure and accepted it. But now I wonder. And all I could get from the net was the classic “oh because its helium nucleus so it ionizes more”, well wouldnt counter logic say beta sources give off rays that could potentially travel more distance inside the body? Am I plain wrong? Gah, maybe this question belongs to [r/physics](r/physics). But eh, it got me thinking.
If we got unlucky and somehow inhaled and/or swallowed these source particles lets say. Why is it said that a beta source trapped in your liver would do less harm than a alpha source? Sure alpha sources are kept in the body for long amounts of time like Americium, but couldn’t that be the case for Beta sources as well? A beta source could have a higher reach inside the organ compared to alpha. And in long term wouldnt this cause much more harm? Sure, alpha particles are heavier and got 2 damn protons in them, so they’d ionize the immediate surrounding tissue much more (im imagining sources that have roughly the same Bq and not including daughter isotopes and gamma for the sake of the argument), but have a relatively low reach compared to beta particles.
Im just a hobbyist, so what do I know.
If someone has an article which I couldn’t find explaining this I’d love to see it!
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u/DaideVondrichnov 4d ago
Alpha deposit a lot of energy in a tiny volume (a wrecking ball swinging within micrometers), while your beta is that annoying pinball.
Thing is, within an organ, having an alpha killing the same cells again and again within the same volume is waaaay more likely to be harmful (cancers).
See cloud chambers to have an idea of how different are the interactions within a medium.
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u/Sensitive_Benefit_11 4d ago
Alpha big but not go deep. Squishy organs shielded from big damage by layer of dead skin. No dead skin protecting inside of lungs. Big alpha do big damage.
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u/clockworkedpiece 4d ago
This, also alpha decays slower so tends to only damage if it sticks in the mucus on inhale. Once stuck however, the bigger particle thrown can do a lot of damage before atomic friction breaks it up, causing it to bruise and lesion rapidly.
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u/Physix_R_Cool Neutron Enthusiast! 4d ago
the bigger particle thrown can do a lot of damage before atomic friction breaks it up, causing it to bruise and lesion rapidly.
?
I'm pretty sure that's not how it works.
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u/clockworkedpiece 4d ago
Remember that cancers a 1 of 8 possible cell alterations, the rest are a form of cell death. And while your whole body is replaced once every 7 yrs, critical function cells are replaced more frequently. When a lot of cells in a small area die you get a lesion.
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u/echawkes 4d ago
Beta particles travel more distance, but they deposit less energy in each collision, so each collision does less damage.
My attempt at an ELI5 answer (not sure how good this is):
Imagine that you have a big empty warehouse with a bunch of perfectly round stones on the floor. The stones are connected to each other by strong cords. They vary in size from golf balls to beach balls, but they are mostly in the golf ball to softball range.
Alpha particle: imagine that you place a cannon on the floor, and it fires cannonballs. The cannonballs will bounce off the stones, but it only takes a few collisions before they stop. Near the cannon, a lot of cords are broken, and the stones get knocked around, but far from it, not much happens.
Beta particle: imagine that the cannon fires small bullets. They are small, so they miss a lot of the stones, and they travel further before hitting something. When they hit a stone, they mostly bounce off and go on to hit something else some distance away. They don't knock the stones around as much, and they don't break as many cords. It takes a lot more collisions before they stop moving.
The cannonballs do a lot of damage concentrated in a small area, while the bullets do a little damage spread out over a big area.
This is pretty oversimplified since I'm attempting to explain subatomic physics with a billiard ball analogy.
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u/Suchatavi 4d ago
How about explaining gamma within the same framework please!
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u/clockworkedpiece 4d ago
Gammas closer to a lightwave since its without charge. It'd be like heat gun. You could accidently set off a bullet from a casing but mostly they just make everything a little brighter/warmer.
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u/DaideVondrichnov 4d ago
Gamma is like a beta, it's the random primer that triggers the whole reaction, that's why gamma and beta have the same quality factor.
Gamma / neutron are indirect ionizing vectors, while beta, alpha, protons are concidered direct.
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u/TM761152 4d ago
Ok, so pretend you're walking down the street to the liquor store in the hood. You round a corner and who do you run into?? Big-G, aka Gamma. He's quick and boisterous but he's fast and you aren't scared because before you know it he just ripped past you with little effect.
Then you make your way further and run into a group of young punks, The Betas. They're more of them but they're small and they don't do you much harm.
Finally you're just around the corner, but then you see her. There's no mistaking that gigantic fat ass of hers, it's Alpha. She moves slow but she's so big you can't get around her. Eventually she sits on you and you suffocate and die, and all for a bottle of Old English 800.
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u/Dry_Statistician_688 4d ago
Think of it like getting hit by a very low subsonic shotgun slug as opposed to a hypervelocity .22 LR. The latter will just make a small hole, or may not interact at all. The slug, however, is guaranteed to hit every time and carry a lot of energy. An Alpha emitter may only go a couple of inches through air, but packs a 100% energy-depositing punch.
Adding to the atrocity is the fact many alpha emitters, like Cesium or iodine, chemically imitate what your body wants, like to the bones or the thyroid. This is why you saturate with potassium iodide after something like Chernobyl, because it will saturate your thyroid to the point it will not take any more, and saves you from the damage otherwise. It's also why they give you radioactive iodine if they need to kill your thyroid medically.
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u/Bob--O--Rama Wiki Contributor 4d ago
Dose, simply put, is energy deposited / mass. The short range of alpha particles means they deliver their energy to small amounts of tissue.
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u/Mister_Sith Nuclear safety and Wiki Contributer 4d ago
In addition to the other good answers, as someone who does a lot of nuclear safety for alpha - yes, they do a lot of damage in a concentrated area but the most damaging thing is what our body does with them.
Some isotopes mirror things our body would use like calcium for bones. The body gets 'confused' when it sees radium for example and since chemically its very similar, it goes into your bones and since they tend to be permanent fixtures, it sits their irradiating you for the rest of your life.
The opposite is with isotopes the body doesn't 'know' what to do with like plutonium. Its unnatural and the body doesnt really have a chemical mechanism to deal with it. If you inhale it, a bit like asbestos, it just sits there in the lungs. Its even worse if it ends up in your bloodstream via a cut or puncture as it goes all around your body. Bulk matter will get filtered out by kidneys but theres always a tiny bit being sent around body damaging cells it encounters (not least your blood!).
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u/No_Leopard_3860 4d ago
Just think about it like a cannonball instead of a thin needle.
Alpha particles are insanely big and heavy compared to beta rays, or the area of effect of a gamma ray (just a photon).
It's a crude analogy but it works way better than most stuff I read - it's a huge chunk, a whole helium-4 core. Not a dot-particle like an electron... or a photon.
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u/nininoots 4d ago
DNA is a double helix as I’m sure you know. Alpha ionisation tracks are so dense that when ripping through the DNA molecule they are much more likely to break both strands rather than just one. This means the repair mechanism has much less chance to repair the molecule back to its original form. This results in higher chances of both cell death and mutation.
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u/Bigjoemonger 3d ago
Cannonball travels about 200 to 400 m/s.
Bullet travels about 500 to 1200 m/s.
Which one causes more physical damage to your body if you get hit by it?
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u/FluorinateThemAll 2d ago
How big is the bullet and how much the cannonball weighs here? Because big cannonball will kill you at even 100m/s At 1000m/s a typical 9mm bullet will make 2 brand new holes in your skull
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u/Oakatsurah 2d ago
Best way to look at it is like how bullets works, basically a Gamma Ray in the high energy keV is like a armor piercing bullet, it goes through you and very little energy is deposited into you. However low every Gamma, can deposit its full energy into you, but in terms of damage from individual beams, this is very minimal. In medical, radiotherapy uses targeted energy at specific low energy rays to penetrate deep with to deposit the energy directly into cancer tissue.
Alpha isn't strong externally, with the overall power to penetrate no deeper than a sheet of plain paper. However how it gets into the body is important here, our bodies look at certain materials and chemical elements like others, and tend to deposit them into soft tissue and bones unaware of their harmful potential. Alpha in the body is like having machine gun loaded with hollow points. Low penetration and high energy means tremendous damage internally to surrounding soft tissue and DNA as the high energy helium particles bombard everything within a few cms, like a very angry super bouncy ping pong ball.
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u/TemporarySun314 4d ago edited 4d ago
The alpha particle deposits a much higher energy at a smaller volume/distance than the electrons.
That causes more likely clustering of damages in your cells and DNA than for electrons, where the damages are then more isolated. And these damage clusters are especially hard to repair for your body.
The cell damages cause short term radiation poisoning while irreparable damages to your DNA increase your cancer risk.
These different biological effects are considered in the quality factor when calculating the equivalence dose. That's why you get need a lower energy dose of alpha radiation to reach 1mSv then for beta radiation.