I am hoping the knowledgeable members of this forum can clear something up for me once and for all, the "danger" of thoriated tungsten filaments.
I am working on an 801A A2 design, I laze about a few different audio forums. Whenever it comes up in discussion, I am warned about my radioactive triodes.
My understanding, and please correct if I am mistaken, is thorium is mildly radioactive, an alpha emitter. Alpha particles cannot penetrate skin and the hazard exists only via ingestion, particularly inhalation. I've noted that thoriated tungsten welding rods are still in use, and it is simply recommended that protection be used when being sharpened due to dust exposure.
I cannot see how an 801A, 845, 211, etc. could cause similar hazard when isolated in a glass bulb.
Can someone clarify if my understanding is accurate? Am I going to grow a third arm sitting a few feet from my amplifier? Thank you.
Edit: further reading, the CDC states that alpha particles pose no danger when outside of the body as they can only penetrate 1 inch of air. I may have answered my own question 🙄
I am working on an 801A A2 design, I laze about a few different audio forums. Whenever it comes up in discussion, I am warned about my radioactive triodes.
My understanding, and please correct if I am mistaken, is thorium is mildly radioactive, an alpha emitter. Alpha particles cannot penetrate skin and the hazard exists only via ingestion, particularly inhalation. I've noted that thoriated tungsten welding rods are still in use, and it is simply recommended that protection be used when being sharpened due to dust exposure.
I cannot see how an 801A, 845, 211, etc. could cause similar hazard when isolated in a glass bulb.
Can someone clarify if my understanding is accurate? Am I going to grow a third arm sitting a few feet from my amplifier? Thank you.
Edit: further reading, the CDC states that alpha particles pose no danger when outside of the body as they can only penetrate 1 inch of air. I may have answered my own question 🙄
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From a presentation by the CDC on the penetrating power of radioactive emission:
Alpha particles may be ejected from the nucleus of an atom during radioactive decay. They are relatively heavy, and only travel about an inch in air. Alpha particles can easily be shielded by a single sheet of paper and cannot penetrate the outer dead layer of skin, so they pose no danger when their source is outside the human body.
Alpha particles may be ejected from the nucleus of an atom during radioactive decay. They are relatively heavy, and only travel about an inch in air. Alpha particles can easily be shielded by a single sheet of paper and cannot penetrate the outer dead layer of skin, so they pose no danger when their source is outside the human body.
Sounds like the thorium in tubes is a lot safer than the Beta and Gamma radiation from potassium (occurring in our bodies).
It is true that thoriated tungsten emits alpha particles when it is heated, machined, welded, etc. As the CDC presentation says, alpha particles can be blocked by a sheet of paper, so when a thoriated tungsten heater is glowing white inside a tube, it is emitting alpha particles that are blocked by the glass tube.
Machinist used to cut beryllium copper (Springs made from BeCu are some of the best springs), but some people develop berylliosis from the Be exposure. Machining thoriated tungsten emits alpha particles, but the particles don't travel far enough and won't be inhaled since most machinists don't stick their nose an inch from the part. Same with depleted uranium.
You're not going to start glowing in the dark because you use vacuum tubes that have thoriated tungsten heater filaments.
Bottom line- you aren't going to be exposed to alpha particles if you have thoriated tungsten tubes in your stereo gear. You get more radiation exposure when you fly in an airplane or get a dental x-ray. Anybody going to stop doing either after the pandemic?
Machinist used to cut beryllium copper (Springs made from BeCu are some of the best springs), but some people develop berylliosis from the Be exposure. Machining thoriated tungsten emits alpha particles, but the particles don't travel far enough and won't be inhaled since most machinists don't stick their nose an inch from the part. Same with depleted uranium.
You're not going to start glowing in the dark because you use vacuum tubes that have thoriated tungsten heater filaments.
Bottom line- you aren't going to be exposed to alpha particles if you have thoriated tungsten tubes in your stereo gear. You get more radiation exposure when you fly in an airplane or get a dental x-ray. Anybody going to stop doing either after the pandemic?
FWIW, radioactive decay occurs at some fixed rate, depending on the specific isotope in question. The commonplace real world physical/chemical environment, like temperature, has zero influence on the rate of decay.
FYI, the half life of thorium 232, the stuff in tube filaments, is (sic) 14.05 billion years. That equates to very few atoms decaying in a massive sized sample, at any given moment. Breathing or ingesting dust containing thorium 232 is dangerous. Otherwise, the stuff is pretty darned safe, especially inside a glass bottle.
FYI, the half life of thorium 232, the stuff in tube filaments, is (sic) 14.05 billion years. That equates to very few atoms decaying in a massive sized sample, at any given moment. Breathing or ingesting dust containing thorium 232 is dangerous. Otherwise, the stuff is pretty darned safe, especially inside a glass bottle.
+1 on what Eli Duttman says
The hazard of machining radioactive materials is in the production of dust which might get into your body and cause damage to sensitive tissues such as the lungs and GI tract. So unless you decide to grind up those filaments and sniff them up your nose there's no issues.
P.S. some bigger tubes have this greenish glass around feedthroughs which is uranium glass. Also not too much of an issue since it is bound inside the glass. People actually collect uranium glassware because it glows under UV
The hazard of machining radioactive materials is in the production of dust which might get into your body and cause damage to sensitive tissues such as the lungs and GI tract. So unless you decide to grind up those filaments and sniff them up your nose there's no issues.
P.S. some bigger tubes have this greenish glass around feedthroughs which is uranium glass. Also not too much of an issue since it is bound inside the glass. People actually collect uranium glassware because it glows under UV
Awesome, so not only aren't my 833C tubes going to kill me, they will also still be thoriated when the sun goes supernova! I can sleep at night now...
Natural uranium is a mix of several isotopes, in which 238 is highly predominate. The half life of uranium 238 is 4.468 billion years. Given the presence of other, less stable, uranium isotopes and decay chain products in a sample, it is (IMO) reasonable to expect approx. 4+ times as many decays per time unit in uranium vs. thorium. Again, the genuine radiation hazard lies in dust inhalation/ingestion. Cancer anyone?
All heavy metals, both stable and radioactive, are chemically toxic to some degree. The toxicity level of bismuth is low enough to make it medicinally useful, while the dangers of mercury, thallium, and lead are very well known. Man made plutonium is a monster, which is both radioactive and incredibly poisonous.
We are constantly exposed to low level space and background radiation. Life on Earth evolved to be adapted to it. Cells possess multiple mechanisms to repair all kinds of radiation damage. Adding a couple of nSv to few uSv does not make any difference.
One of the discoverers of (commercial catalyst for) polyethylene is my grand-uncle Bob. Grandmother had a large orange salad bowl he made from an early batch of PE. The color was Uranium Oxide. Beautiful!! At the time U-oxide was widely used for coloring ceramic glazes. We all ate out of it. Later Bob told grandmother not to use the bowl for food because PE doesn't seal as well as ceramic glaze.
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Fiestaware? Personally I'm not much of a fan of ceramics and radioactive materials because during usage they get scratched which makes dust which you eat. Your uncle Bob was a smart guy for warning her!
Uranium glass is kind of cool though as it makes really good metal-glass seals. And if there is some UV it also glows very pretty 🙂
Uranium glass is kind of cool though as it makes really good metal-glass seals. And if there is some UV it also glows very pretty 🙂
Alas not quite, as thoriated materials emit both alpha and beta particles, not just alpha.
The thorium decay series includes 11 alpha and beta emitting isotopes, all but Th232 have very short half-lifes, so anything with thorium will emit both alpha and beta particles of various energies. However neither kind will get through a glass envelope. Decay chain - Wikipedia
In fact since most of the alpha particles will fail to escape the tungsten due to their low penetrating power I'd expect in practice a thoriated tunsten electrode to produce mainly beta particles.
Thorium is everywhere on Earth. When it decays, the byproducts are radon, among other radionuclides. Anybody heard of radon?
Worrying about being exposed to alpha, beta or gamma radiation from a vacuum tube containing thoriated tungsten is useless. There are a lot of other radionuclides to worry about.
Just like people worried about the Yucca Mountain Site in NV introducing high level radioactive materials into the state of Nevada.
Nevada already has a high level radioactive material site. It's formerly known as the Nevada Test Site. Over 1200 nuclear detonations were conducted from the 1940's until 1992. Most of them were underground tests.
Where do people think the radioactivity went?
Worrying about being exposed to alpha, beta or gamma radiation from a vacuum tube containing thoriated tungsten is useless. There are a lot of other radionuclides to worry about.
Just like people worried about the Yucca Mountain Site in NV introducing high level radioactive materials into the state of Nevada.
Nevada already has a high level radioactive material site. It's formerly known as the Nevada Test Site. Over 1200 nuclear detonations were conducted from the 1940's until 1992. Most of them were underground tests.
Where do people think the radioactivity went?
Its the uranium decay series, not the thorium decay series, that makes the vast majority of radon (Rn222 specifically), due to the much longer half-life of Rn222.
The key point about these very low-level radiactive materials is to avoid routes of entry into the body, such as breathing or ingesting dust particles. So the take-home message is don't play with the material, leave it in the tube and dispose of safely.
And if you've never heard of radon, its worth checking the maps to see if you life in a high radon area and if so check out mitigation steps, especially if you live on the ground floor or a basement - that's a bigger hazzard.
The key point about these very low-level radiactive materials is to avoid routes of entry into the body, such as breathing or ingesting dust particles. So the take-home message is don't play with the material, leave it in the tube and dispose of safely.
And if you've never heard of radon, its worth checking the maps to see if you life in a high radon area and if so check out mitigation steps, especially if you live on the ground floor or a basement - that's a bigger hazzard.