Radiation Safety: Understanding Exposure and Risk

AI Thread Summary
Touching the ionization chamber of a smoke detector does not significantly increase cancer risk, as the radiation emitted by americium-241 is primarily alpha particles, which cannot penetrate skin. Concerns about dust from the decay of americium are unfounded, as it does not produce dust that can escape the chamber. The radioactive material is securely encapsulated, and any potential exposure is minimal unless the detector is intentionally damaged. The risk of radiation exposure is negligible compared to the fire safety benefits provided by smoke detectors. It is recommended to replace old smoke detectors, especially those over ten years old, to ensure safety.
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Recently when cleaning, I opened the cover of our ionisation smoke detector and as I was touching all around the inside of the smoke detector with my bare hands and most importantly including all the sides of the ionization chamber with the radiation symbol on it which contains the radiation, for around 5-6 minutes, have I:-
  1. Increased my risk of taking cancer now or in future from touching the outside of the ionization chamber with the radiation-would there have been a lot of exposure?
  2. By touching the ionization chamber (which is black on the outside-perhaps hard plastic) could I have loosened it in any way allowing the radiation to be exposed and to escape into the house? This is a big concern for me.
  3. Can the radiation easily become loose or fall out of the ionisation chamber?
  4. Would dust on my hands afterwards just have been household dust or was it from the radiation? More to the point does the decay of americium-241 produce dust
  5. As there are slats on the side of the ionisation chamber, could dust from the americium escape here?
This panicked me when I realized I had been touching the actual ionisation chamber and I wanted some information on the safety.
 
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spark90 said:
Recently when cleaning, I opened the cover of our ionisation smoke detector and as I was touching all around the inside of the smoke detector with my bare hands and most importantly including all the sides of the ionization chamber with the radiation symbol...
Do you have a make and model or pictures of this smoke detector? Because mine are not designed to be opened, and I see no obvious way to even do it without breaking it.
1. Increased my risk of taking cancer now or in future from touching the outside of the ionization chamber with the radiation-would there have been a lot of exposure?
No.
2. By touching the ionization chamber (which is black on the outside-perhaps hard plastic) could I have loosened it in any way allowing the radiation to be exposed and to escape into the house? This is a big concern for me.

3. Can the radiation easily become loose or fall out of the ionisation chamber?

4. Would dust on my hands afterwards just have been household dust or was it from the radiation? More to the point does the decay of americium-241 produce dust.

5. As there are slats on the side of the ionisation chamber, could dust from the americium escape here?
That's...not what "radiation" is. In this case, it's a free helium atom nucleus, not a dust. There isn't enough Americium in a smoke detector to be harmful in any way, and in any case the radiation (alpha particles) can't penetrate your skin.
 
Americium is the source that's chosen as it's a good source of Alpha Particles (doubly ionised Helium Nuclei). These are massive great particles and, once they have slowed down in the detector, they become harmless Helium Atoms. No Beta Particles or gamma photons.
I think that. nowadays, anything that's radioactive and for use by the public will have passed a lot of risk assessments. I guess that eating the source could be a finite risk but the Alpha source can only damage tissue that out actually come into contact with. I guess the cell would pass straight through.

I would say that the risk of any possible radiation injury is totally insignificant, compared with the reduction of risk of injury or death in a fire.
 
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If you read the labels carefully, you should see, "Do not ingest." I assume you didn't eat it, correct? Then you should be OK.
 
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anorlunda said:
If you read the labels carefully, you should see, "Do not ingest." I assume you didn't eat it, correct? Then you should be OK.

No, I was just concerned that the dust into my eyes and hence was inhaled when I opened the smoke detector cover was dust from the decay of the americium inside the smoke detector.
 
sophiecentaur said:
Americium is the source that's chosen as it's a good source of Alpha Particles (doubly ionised Helium Nuclei). These are massive great particles and, once they have slowed down in the detector, they become harmless Helium Atoms. No Beta Particles or gamma photons.
I think that. nowadays, anything that's radioactive and for use by the public will have passed a lot of risk assessments. I guess that eating the source could be a finite risk but the Alpha source can only damage tissue that out actually come into contact with. I guess the cell would pass straight through.

I would say that the risk of any possible radiation injury is totally insignificant, compared with the reduction of risk of injury or death in a fire.
Thank you for your reply. As my smoke detector is 27 years old I was worried health and safety wasn't as good then. As dust from the inside of the cover could have been inhaled when falling into my eyes, are you aware of whether when americium decays over the years does it produce dust and could this have been the dust i encountered as it states online inhalation of this dust collects in lungs.
 
russ_watters said:
Do you have a make and model or pictures of this smoke detector? Because mine are not designed to be opened, and I see no obvious way to even do it without breaking it.

No.

That's...not what "radiation" is. In this case, it's a free helium atom nucleus, not a dust. There isn't enough Americium in a smoke detector to be harmful in any way, and in any case the radiation (alpha particles) can't penetrate your skin.
Thank you for your reply. As my smoke detector is 27 years old I was worried health and safety wasn't as good then. As dust from the inside of the cover could have been inhaled when falling into my eyes, are you aware of whether when americium decays over the years does it produce dust and could this have been the dust I encountered as it states online inhalation of this dust collects in lungs.
Also can dust/alpha escape the slats at the sides of the ionisation chamber?
Here is what my detector looks like attached.
 

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I would expect zero dust. The Americium is encapsulated in a coating.

In the days of the Manhattan Project, plutonium was extra dangerous because of spontaneous sintering that shed dust, contaminating the room and everything in the room. But soon after WWII, the bomb makers learned that a simple coating eliminated that specific problem.

Here's a declassified picture from a hydrogen bomb factory.

1614894180773.png
 
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spark90 said:
As my smoke detector is 27 years old I was worried health and safety wasn't as good then.
Well that's a concern; please check it, because it may have a 10-year lifespan. That's a significant safety risk if it is expired.
As dust from the inside of the cover could have been inhaled when falling into my eyes, are you aware of whether when americium decays over the years does it produce dust...
It does not.
Also can dust/alpha escape the slats at the sides of the ionisation chamber?
It's not dust. Yes, at least some of the alpha particles escape.
 
  • #10
russ_watters said:
That's a significant safety risk if it is expired.
OMG. Risk of burning and nuclear radiation at the same time. Get A New One PDQ.
 
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  • #11
sophiecentaur said:
OMG. Risk of burning and nuclear radiation at the same time. Get A New One PDQ.

Not sure what you mean by that. I have anxiety and sm just looking reassurance, what do you mean risk of nuclear radiation?
 
  • #12
Most smoke detectors use americium-241 as their source. Some early models used radium-226, and commercial smoke detectors and some residential units used nickel-63. The types of radiation from these sources cannot make anything else radioactive.
  • Ni-63 emits beta particles, which can travel a few feet but cannot penetrate a smoke detectors plastic housing.
  • Am-241 and Ra-226 primarily emit alpha particles. These particles only travel a few inches, are easily stopped and only present a health hazard if taken into the body.
  • Am-241 and Ra-226 also emit gamma radiation in an amount so low it cannot be distinguished from natural radiation from space and the earth.
The radioactive sources are in a form that does not break down or corrode over time. The source is sandwiched between two layers of metal and rolled thin. This "foil" is sealed inside the ionization chamber. The seal can only be broken by the deliberate use of force, such as taking a hammer to the smoke detector. The NRC discourages this kind of intentional destruction. In a fire, the sources would release less than 0.1 percent of their radioactivity.
US NRC
Smoke detector internals.
 
  • #13
spark90 said:
Not sure what you mean by that. I have anxiety and sm just looking reassurance, what do you mean risk of nuclear radiation?
Sorry if I upset you but you have already been given plenty of reassurance with good information about the actual risk of radioactive exposure. But using the same smoke detector for all that time could be regarded as foolhardy. It's all a matter of getting risks in proportion and the risk of an undetected fire is something that can be taken care of easily by a trip to the DIY shop. If you are concerned by radiation risks then buy a type of smoke detector that doesn't use a radioactive source.
Afaics, the most important thing for you is to get a new detector PDQ (and you could check on your CO detector if you have one - the lifetime of those is very limited)
 
  • #14
russ_watters said:
Do you have a make and model or pictures of this smoke detector? Because mine are not designed to be opened, and I see no obvious way to even do it without breaking it.

No.

That's...not what "radiation" is. In this case, it's a free helium atom nucleus, not a dust. There isn't enough Americium in a smoke detector to be harmful in any way, and in any case the radiation (alpha particles) can't penetrate your skin.
In regards to you said "thats not what radiation is", I am just interested what you mean by that, thanks
 
  • #15
spark90 said:
In regards to you said "thats not what radiation is", I am just interested what you mean by that, thanks
Well you keep asking if it's dust and also don't seem to be distinguishing between radiation and radioactive material.
 
  • #16
russ_watters said:
Well you keep asking if it's dust and also don't seem to be distinguishing between radiation and radioactive material.

I am just a member of the public and know nothing about radiation. I just assumed amercium decays over time and would produce dust which could escape the slats of the ionisation chamber. Sorry I have anxiety and looking for some facts.
 
  • #17
spark90 said:
I am just a member of the public and know nothing about radiation. I just assumed amercium decays over time and would produce dust which could escape the slats of the ionisation chamber. Sorry I have anxiety and looking for some facts.
I know - that was just an answer to your question.
 
  • #18
russ_watters said:
I know - that was just an answer to your question.

Thank you really appreciate your time, still don't understand really if americium breaks down to produce dust which can escape the ionisation slats-could you briefly explain that...and I promise that is my last question. You are very kind taking the time to reply.
 
  • #19
spark90 said:
I am just a member of the public and know nothing about radiation. I just assumed amercium decays over time and would produce dust which could escape the slats of the ionisation chamber. Sorry I have anxiety and looking for some facts.
When a radioactive decay occurs (in this case an alpha decay), the parent atom emits the daughter particle and, as a result, becomes a different type of atom. One can look up Americium 241 on wikipedia and find that the alpha decay results in Neptunium 237.

The alpha particle is essentially a Helium nucleus. Two protons and two neutrons. No electrons, so it has a charge of +2 from the protons. The "radiation" is the alpha particle.

The loss of two protons and two neutrons means that the result (Neptunium) has an atomic number that is two less than that of Americium. If you look at the periodic table you'll find Americium and Neptunium on the bottom row with Neptunium at atomic number 93, two slots to the left of Americium with atomic number 95 just as one would expect.

Now I am just a school boy physics geek and know not too much about the engineering or chemistry of this stuff, but I'd expect that the result of the decay of the Americium dioxide within a pellet to result quickly in a molecule of Neptunium dioxide still within the same pellet. One would expect the designers to have arranged for the decay not to result in decay products falling clear of the original matrix.

But in any case, the Neptunium 237 is much less radioactive than Americium 241. By a factor of half a million to one. (Based on a comparison of half-lives).
 
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  • #20
jbriggs444 said:
When a radioactive decay occurs (in this case an alpha decay), the parent atom emits the daughter particle and, as a result, becomes a different type of atom. One can look up Americium 241 on wikipedia and find that the alpha decay results in Neptunium 237.

The alpha particle is essentially a Helium nucleus. Two protons and two neutrons. No electrons, so it has a charge of +2 from the protons. The "radiation" is the alpha particle.

The loss of two protons and two neutrons means that the result (Neptunium) has an atomic number that is two less than that of Americium. If you look at the periodic table you'll find Americium and Neptunium on the bottom row with Neptunium at atomic number 93, two slots to the left of Americium with atomic number 95 just as one would expect.

Now I am just a school boy physics geek and know not too much about the engineering or chemistry of this stuff, but I'd expect that the result of the decay of the Americium dioxide within a pellet to result quickly in a molecule of Neptunium dioxide still within the same pellet. One would expect the designers to have arranged for the decay not to result in decay products falling clear of the original matrix.

But in any case, the Neptunium 237 is much less radioactive than Americium 241. By a factor of half a million to one. (Based on a comparison of half-lives).

Thanks for your time, I was really just wanting to know a simple answer to whether americium decays over the years producing dust which can escape the ionisation chamber. Thanks again
 
  • #21
spark90 said:
I was really just wanting to know a simple answer to whether americium decays over the years producing dust which can escape the ionisation chamber
No.
 
  • #22
spark90 said:
I was really just wanting to know a simple answer to whether americium decays over the years producing dust
The Americium is embedded in a block of plastic. No atoms of anything leave that block of plastic - except for high speed Helium nuclei. They will travel just far enough to operate the detector (perhaps 1mm) and then they are stopped. They can no longer be regarded as Radioactive products but will find their way out into the atmosphere or get embedded in the case of the detector. The case cannot become 'radioactive' when that happens.
I can't help thinking you are finding it a bit of a disappointment that the situation is not slightly risky. The only way you could get damaged by the Americium could be if you shredded / crushed the source and then embedded it into your brain, lungs or gut. I have already made the point that the risk of injury or death through an undetected fire is seriously significant. You need to get your priorities in proper balance. One small slip in your (I hope) scrupulous behaviour regarding Covid-19 puts you in far more danger than anything from that smoke detector.
 
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  • #23
sophiecentaur said:
You need to get your priorities in proper balance. One small slip in your (I hope) scrupulous behaviour regarding Covid-19 puts you in far more danger than anything from that smoke detector.

Well, since you urged being quantitative, I don't think this is true for most people. Under 50 years old, your odds of dying of Covid are 10x the odds of dying in fire. I don't know what "far more danger" means - a factor of 2? That would mean "one small slip" needs to increase your risk by at least 20% or so. That doesn't sound like a "small slip".

So, while I think this isn't the best example, I agree with the sentiment that risks need to be quantified, and that the risk of an alpha source (unless you break it apart and eat it, or something equally insane) is less than the risk of fire.
 
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  • #25
spark90 said:
I am just a member of the public and know nothing about radiation. I just assumed amercium decays over time and would produce dust which could escape the slats of the ionisation chamber. Sorry I have anxiety and looking for some facts.
Radiation is the energy emission of electromagnetic waves or subatomic particles. Therefore, heat, light, and electricity are examples of radiation. When you go to the beach to get a suntan, ultraviolet radiation from the sun hitting your skin causes that. When you feel your skin warming up, that is from infrared radiation from the sun. When you go to the dentist and get an x-ray performed, that is done from high-energy waves when penetrate your skin and muscle and expose the film on the other side.
Radiation comes in two flavors, ionizing and non-ionizing. Ionizing radiation is basically the type of radiation that turns something into ions. Atoms or molecules affected by ionization are turned into ions through the loss of electrons from high speed particulars "radiating" the substance. The radiation emitted from an atomic bomb is an example of ionizing radiation. The sun also produces ionizing radiation in the form of x-rays and gamma rays.
An example of non-ionizing radiation is the energy emitted from your microwave oven. The microwave oven converts electricity to electromagnetic waves (e.g., microwaves). These waves makes molecules (typically water in your food) to "bounce" around causing heat. In turn, any food that has sugars or fats will be heated from the heated water molecules.
Radioactive material, on the other hand, is material that has nuclides that degenerate spontaneously releasing radiation. A good example of this is radium which is found naturally in rocks such as uranium (itself being a radioactive material) and even granite. As the radium decays, it releases radon gas, which is why it is good to check for radon levels in your home that can seep from the bedrock underneath the foundation.
So, the next time you turn on a flashlight, the light you produced is radiation. The same is true for a candle you lit. And, the heat emanating from the candle is also radiation. And, when you walk in the countryside, pick up a rock. It might be radioactive material, though not dangerous (most likely).
 
  • #26
Vanadium 50 said:
Under 50 years
I wish!
Vanadium 50 said:
your odds of dying of Covid are 10x the odds of dying in fire.
I was referring to the odds of injury due to the contents of the detector - but I could have made it clearer.
 
  • #27
sophiecentaur said: "OMG. Risk of burning and nuclear radiation at the same time. Get A New One PDQ."

Sophiecentaur was making a serious joke.
No, your smoke detector is not a source of hazardous radiation.
But the manner in which it works is that the decaying radioactive element sends energy toward a receiver. The particulates in smoke block the energy from reaching the receiver, setting it off.

Now regulators make sure consumer products are built to the lowest common denominator, i.e. what's the STUPIDEST thing a consumer can do, and will that be lethal? So the detector has a very small quantity of radioactive material in it to work--but radioactive materials decay over time--half-lives. And they become less radioactive, by half, as they degrade, putting out half the energy they did the period before. The common 10 year life let's the detector do its work while never being a source of energy that could ever be hazardous.

At 27 years old, there is a very, very good chance your detector wouldn't actually go off in a fire: its source has gotten too weak to do its job, or the receiver isn't working right, or it didn't have the annoying warnings that modern ones have to warn you they are NFG.

You should replace that thing, pronto.
It may be giving you a false sense of security.
There's a high probability at 27 years old that it is NFG.
 
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  • #28
N1206 said:
So the detector has a very small quantity of radioactive material in it to work--but radioactive materials decay over time--half-lives. And they become less radioactive, by half, as they degrade, putting out half the energy they did the period before. The common 10 year life let's the detector do its work while never being a source of energy that could ever be hazardous.

At 27 years old, there is a very, very good chance your detector wouldn't actually go off in a fire: its source has gotten too weak to do its job, or the receiver isn't working right, or it didn't have the annoying warnings that modern ones have to warn you they are NFG.
The half life is unlikely to be the issue. For Americium 241 the half-life is 432 years. You may be right about the reliability of the receiver.
 
  • #29
These ionization smoke alarms are alerting tens of minutes slower than the other type, photoelectric smoke alarms, in the deadly smoldering stage of a fire. They are also more prone to nuisance false alarms from ordinary cooking and steam from showers.

Photoelectric smoke alarms sound tens of minutes faster than ionization smoke alarms during smoldering stage fires with significantly fewer false alarms. Furthermore, their performance in flaming stage fires is comparable to ionization alarms, making the photoelectric alarm the best choice.
https://neofpa.org/smoke-alarms/half-smoke-alarms-fail/
 
  • #30
Can I say a massive thanks to everyone for replying I really appreciate it. The reason I went on a bit was because I read on another site a post that concerned me:- "It is the alpha recoil reaction that can destroy the thin coating over the source and allow source material to recoil out of the source." Apparently this caused a yellow discharge from someone's ionisation chamber, although the activity was 5 microcuries. That was why I asked so many questions on here because I know so many of you were experts. Thanks again
 
  • #31
spark90 said:
because I read on another site a post that concerned me:
It would have been a good idea to have quoted that in your first post. :smile:
 
  • #32
Yeah that is true. I just wasn't sure if it sounded daft or whether it was reasonable
 
  • #33
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  • #34
Good day.

As a Radiation Protection Specialist, with 30 years of experience, I can assure you that the risk to you, from fiddling with the Americium-241 source inside your smoke detector, is negligible. The quantity of radioactivty in such a detector is, in regulatory jargon, Exempt from being regulated. This means that the radiation dose, which anyone can be exposed to, by fiddling with the source, is considered too small to cause any harm. Yes, this does come from very detailed risk assessments which have considered ALL potential scenarios of "playing with the source" and the resultant radiation dose. Wherever you are living, if it was considered that the smoke detector could be harmful it would never have been sold to you as a member of the general public. I hope this puts your mind at ease. Of course, there's no harm in washing your hands after touching the source which I am sure that you did. If you didn't the potential radiation dose would still be negligible.

Paul
 
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  • #35
Having said that, it's good practice to keep away from radiation if you can avoid it. That's easier said than done as radioactivity is a natural phenomenon and we are all surrounded by it every day without even being aware.
 
  • #36
Phinrich said:
Good day.

As a Radiation Protection Specialist, with 30 years of experience, I can assure you that the risk to you, from fiddling with the Americium-241 source inside your smoke detector, is negligible. The quantity of radioactivty in such a detector is, in regulatory jargon, Exempt from being regulated. This means that the radiation dose, which anyone can be exposed to, by fiddling with the source, is considered too small to cause any harm. Yes, this does come from very detailed risk assessments which have considered ALL potential scenarios of "playing with the source" and the resultant radiation dose. Wherever you are living, if it was considered that the smoke detector could be harmful it would never have been sold to you as a member of the general public. I hope this puts your mind at ease. Of course, there's no harm in washing your hands after touching the source which I am sure that you did. If you didn't the potential radiation dose would still be negligible.

Paul
That is very good of you to reply thank you so much. As you are an expert could you explain a post I saw on another forum which stated " It is the alpha recoil reaction that can destroy the thin coating over the source and allow source material to recoil out of the source." Apparently this caused a yellow discharge from someone's ionisation chamber which collected as a dust around the ionisation chamber, although the activity was 5 microcuries. " Could this occur in my smoke detector which is 27 years old and 0.9 microcuries. I was concerned as dust fell in my eye when I opened the detector and was worried when I read that the thin metal seal on the source can breakdown due to alpha particles over time and hence release the decay products and was worried this had came out of the ionisation chamber due to the age of my smoke detector. Thanks again
 
  • #37
Off the top of my head, I would answer as follows.

Firstly, I am not encouraging you to eat the Americium 241 source, but when I say that the exemption of the source (based on a level of 5 mico-curies activity), is based upon assessing all possible ways for you to be exposed to it, that would include you eating the source. That's shocking to say and I am by no means suggesting that anyone should do this. Still, someone has done a calculation to determine what radiation dose would be received by such a foolish act and they have determined it to be negligible. In such a scenario the source would most likely be expelled from the body along the digestive tract and pass harmlessly out.

Speaking about the "disintegration of the source", if we ignore any "break-up" of the source (recoil and all that), what it means to say that the source is radioactive means that every second it shoots out, in this case, alpha particles (helium nuclei) and thereby leaves behind less radioactivity. A 5 micro-Curie source will emit 200 000 alpha particles every second (to begin with). Do not be frightened by this large number as most of these alpha particles will get stopped by air molecules immediately around the source without exiting the chamber of the detector (assuming no holes in the chamber outer wall). Even if there is a hole or two in the chamber walls alpha particles do not carry a lot of energy and again will collide with millions of air molecules as they travel and will very soon lose all their energy. Americium-241 has a half-life of 432 years. What this means is, if we could count the number of alpha particles emitted per second, today, and get 200 000, then 432 years later, if we measured, we would get 100 000 alphas per second (half of the original amount). After another 432 years, we would get 50 000 and so on. I agree that there may be mechanisms for the casing of the detector to break-down. The question of the possibility of alpha-recoil I see as a pure physics question which I will leave to the physicists to answer. The point is, should there be breaks in the outer casing of the detector which allow the escape of source material (speaking here about small fragments of the source rather than emitted alpha particles as we have said that alpha particles do not travel very far in the air). If small fragments of the source material do escape (by breaking off the source due to age) and even if those fragments got into your eye, these fragments (dust) would continue to emit alpha particles in your eye. However, these alpha particles would not get deeper than the first tissue layer of the eye before being stopped. It is not the alpha particle that causes tissue damage leading to radiation damage, it is the ënergy carried by a moving alpha particle. A moving alpha particle may be thought of as a small moving bullet. However, the bullet very soon loses energy and stops moving. A bullet that is not moving cannot do any damage. Once the moving alpha particle has lost its energy, by colliding with the more dense tissue in the first layer of tissue of the eye, they lose their ability to cause any radiation damage to the eye or to any other part of the body. The "dead" alpha particles will then most likely be washed out of your eye by natural tears or be absorbed into your tissue harmlessly. So yes we are surrounded by natural radiation, and as a member of the public, you may be exposed to many different sources of radiation. For example, exposure to your smoke detector or a visit to the doctor resulting in an X-ray image being taken. According to international standards, as a member of the public, you are allowed a total radiation dose of 1 millie Sievert per year, from all sources, without it being considered harmful to you. As a Radiation Protection Specialist, I work with radioactivity almost daily. I wear a radiation monitor which records my daily dose. I am allowed a total of 20 milli Sieverts per year (20 x your dose) without it ever being considered harmful to me. In my 30 years of doing this job I have never ever gotten anywhere near to 20 millie Sieverts radiation dose in a single year.

I hope this is helpful and please feel free to ask more questions.

Paul
 
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  • #38
Speaking of having radioactive material inside your eye, in an earlier job I worked as a medical physicist at a large hospital with a radiotherapy Unit. There is a rare condition known as Retinoblastoma which leads to a cancer tumour inside the patient's eyeball. We would treat this condition (very successfully) by purposefully placing radioactive Iodine-125 sources inside the patient's eye socket to give radiation to the tumour. The geometric arrangement of the sources was very carefully calculated on a computer and we used more than 5 micro Sieverts of activity for each such procedure. After a calculated number of days, the sources were removed and the tumour was successfully treated and the patient's eyesight was saved.

Paul
 
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  • #39
Phinrich said:
Speaking of having radioactive material inside your eye, in an earlier job I worked as a medical physicist at a large hospital with a radiotherapy Unit. There is a rare condition known as Retinoblastoma which leads to a cancer tumour inside the patient's eyeball. We would treat this condition (very successfully) by purposefully placing radioactive Iodine-125 sources inside the patient's eye socket to give radiation to the tumour. The geometric arrangement of the sources was very carefully calculated on a computer and we used more than 5 micro Sieverts of activity for each such procedure. After a calculated number of days, the sources were removed and the tumour was successfully treated and the patient's eyesight was saved.

Paul

Thank you for your replies. Those are very detailed answers you gave me. I was only asking because I had read online of a 1970's smoke detector which had leaked a yellow dust which was covering the ionisation chamber and the physicist replied that it was due to the alpha recoil breaking down the seal over the americium that meant that the decay product of Np could escape and this was the yellow dust and hence I read it is very dangerous to inhale such things and I obviously would have inhaled falling dust!
 
  • #40
Hope the answers were not too detailed. I was trying to put your mind at ease. I agree with the Physicist regarding where the yellow dust could have come from and also I agree that it is "dangerous" in the sense that, although the quantity of radioactivity is small, it's a good policy to keep away from it if you can.
 
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  • #41
Phinrich said:
Hope the answers were not too detailed. I was trying to put your mind at ease. I agree with the Physicist regarding where the yellow dust could have come from and also I agree that it is "dangerous" in the sense that, although the quantity of radioactivity is small, it's a good policy to keep away from it if you can.

So you think that the yellow dust on the inner cover of my smoke detector was emitted through the ionisation chamber by the decay of the americium?
 
  • #42
I am afraid I have very little experience with Americium smoke detectors. Although I work for my countries nuclear regulator the regulation of smoke detectors is handled by another regulator. I have spoken to you about the principles and practice of radiation protection, in general. My point was that if your government allows these devices into your home then it is because they are known to be safe. Without knowing the composition of the dust I cannot say where it came from. I have no experience to confirm that the Americium source could break-up as it ages physically. I guess it could. And maybe it does lead to a powder on the outside of the detector. Having no experience I would not want to confirm it positively. I suggest you possibly talk to the supplier. Or perhaps someone with the right experience could join the conversation. If Americium sources can break-up and lead to powders which you could ingest, and if this ingestion was dangerous your government would not allow you to have them inside your house.
 
  • #43
Phinrich said:
I am afraid I have very little experience with Americium smoke detectors. Although I work for my countries nuclear regulator the regulation of smoke detectors is handled by another regulator. I have spoken to you about the principles and practice of radiation protection, in general. My point was that if your government allows these devices into your home then it is because they are known to be safe. Without knowing the composition of the dust I cannot say where it came from. I have no experience to confirm that the Americium source could break-up as it ages physically. I guess it could. And maybe it does lead to a powder on the outside of the detector. Having no experience I would not want to confirm it positively. I suggest you possibly talk to the supplier. Or perhaps someone with the right experience could join the conversation. If Americium sources can break-up and lead to powders which you could ingest, and if this ingestion was dangerous your government would not allow you to have them inside your house.

Thank you, you have been really generous with your time. Very grateful!
 
  • #44
It's a pleasure. It is 22:30 here and I am retiring for the night. If you ask more questions I will answer them tomorrow. Have a GREAT day.
 
  • #45
The following link may be of interest to you;

https://valueguardinspections.com/h...etectors are an,and likely should be replaced.

It states that old smoke detectors often turn yellow because smoke detector manufacturers often inject a fire retardant bromine into the plastic of residential smoke detectors. Bromine serves a dual purpose. It helps protect the unit in the event of a fire and also serves as a visual signal the detector is older and likely should be replaced.
 
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Likes Klystron and hmmm27
  • #46
On the matter of 'have I increased my risk of cancer', I seem to recall seeing other threads along similar lines recently.

The answer to 'that' side of the question is that a little exposure to ionising radiation appears to be good for humans. They have evolved to live and thrive on a planet showered with high energy cosmic radiation, and apparently there is some response from the cell genetics to 'a little' radiation that is not simply unharmful but positively beneficial.

The assumption that 'any' radiation is bad for you is a cautionary one as it is better to assume that 'nothing' of something bad is optimum if one has no idea of the detail, which was the case in the early days.

It's pretty clear now that exposure to radiation is bimodal and does not follow a straight line path of cancer-causality for small dose cases (as would be the case here) in the order of background levels.

Rates of cancer in the world are generally inversely related to the natural background radiation.

Radiation is a hidden bogey-may/invisible monster and therefore invokes fear. This is understandable. But trust the science and engineering. A smoke detector is designed to package away harmful radioactive materials from commonly prying hands.
 
  • #47
Thank you for your comment. You are ABSOLUTELY correct. We are exposed to little bits of radiation every day and the species has been exposed for millennia and it is certainly possible that a little radiation is good for us and may in fact help with the evolution of the species. I didn't want to get into all of that yesterday but I do agree with you. Thank you for adding that.
 
  • #48
Phinrich said:
a little radiation is good for us and may in fact help with the evolution of the species
The same has been said of extinction events.
:smile:
 
  • #49
TRUE! That's a GOOD one. I'd rather take my chances with a little radiation than with a little extinction THANK YOU! At least until Mr. Musk gets us colonizing Mars.
 
  • #50
Phinrich said:
Off the top of my head, I would answer as follows.

Firstly, I am not encouraging you to eat the Americium 241 source, but when I say that the exemption of the source (based on a level of 5 mico-curies activity), is based upon assessing all possible ways for you to be exposed to it, that would include you eating the source. That's shocking to say and I am by no means suggesting that anyone should do this. Still, someone has done a calculation to determine what radiation dose would be received by such a foolish act and they have determined it to be negligible. In such a scenario the source would most likely be expelled from the body along the digestive tract and pass harmlessly out.

Speaking about the "disintegration of the source", if we ignore any "break-up" of the source (recoil and all that), what it means to say that the source is radioactive means that every second it shoots out, in this case, alpha particles (helium nuclei) and thereby leaves behind less radioactivity. A 5 micro-Curie source will emit 200 000 alpha particles every second (to begin with). Do not be frightened by this large number as most of these alpha particles will get stopped by air molecules immediately around the source without exiting the chamber of the detector (assuming no holes in the chamber outer wall). Even if there is a hole or two in the chamber walls alpha particles do not carry a lot of energy and again will collide with millions of air molecules as they travel and will very soon lose all their energy. Americium-241 has a half-life of 432 years. What this means is, if we could count the number of alpha particles emitted per second, today, and get 200 000, then 432 years later, if we measured, we would get 100 000 alphas per second (half of the original amount). After another 432 years, we would get 50 000 and so on. I agree that there may be mechanisms for the casing of the detector to break-down. The question of the possibility of alpha-recoil I see as a pure physics question which I will leave to the physicists to answer. The point is, should there be breaks in the outer casing of the detector which allow the escape of source material (speaking here about small fragments of the source rather than emitted alpha particles as we have said that alpha particles do not travel very far in the air). If small fragments of the source material do escape (by breaking off the source due to age) and even if those fragments got into your eye, these fragments (dust) would continue to emit alpha particles in your eye. However, these alpha particles would not get deeper than the first tissue layer of the eye before being stopped. It is not the alpha particle that causes tissue damage leading to radiation damage, it is the ënergy carried by a moving alpha particle. A moving alpha particle may be thought of as a small moving bullet. However, the bullet very soon loses energy and stops moving. A bullet that is not moving cannot do any damage. Once the moving alpha particle has lost its energy, by colliding with the more dense tissue in the first layer of tissue of the eye, they lose their ability to cause any radiation damage to the eye or to any other part of the body. The "dead" alpha particles will then most likely be washed out of your eye by natural tears or be absorbed into your tissue harmlessly. So yes we are surrounded by natural radiation, and as a member of the public, you may be exposed to many different sources of radiation. For example, exposure to your smoke detector or a visit to the doctor resulting in an X-ray image being taken. According to international standards, as a member of the public, you are allowed a total radiation dose of 1 millie Sievert per year, from all sources, without it being considered harmful to you. As a Radiation Protection Specialist, I work with radioactivity almost daily. I wear a radiation monitor which records my daily dose. I am allowed a total of 20 milli Sieverts per year (20 x your dose) without it ever being considered harmful to me. In my 30 years of doing this job I have never ever gotten anywhere near to 20 millie Sieverts radiation dose in a single year.

I hope this is helpful and please feel free to ask more questions.

Paul
You are the absolute god of explanations. Your narrative was like ASMR for the intellect.
 
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