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Thread: Contaminated

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    Default Contaminated

    Local recyclers had some lead containers which looked very nice condition. I wondered if they might be an alloy because they didn't look like the old bits of lead I have, looked more like babbit bearings I've got but maybe they just hadn't corroded. There were some painted metal containers too, which were much thinner. The lead ones were about 3" across and maybe 20mm thick. The metal ones were much narrower. They had come from a hospital and my guess was they had held radioactive sources. I didn't take any home, but they were tempting. Would have made a nice lead hammer and the metal containers looked very strong for protecting small items.

    I did some reading later and I think lead can't become radioactive itself, unless there is actually some radioactive material on the surface. The thing I read also said they would have been checked carefully before disposing but it was safe to dispose of (although lead shouldn't be dumped). I don't have any means to check so I left them. Any opinions on how safe they might have been?

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    BobL is offline Member: Blue and white apron brigade
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    Correct about the lead itself not being able to become radioactive on exposure to the sorts of things used in hospitals.
    In terms of spilt radioactive materials, the containers should be fine. They absolutely have to be check out before disposal and are usually used to store short half life materials so if they were ever contaminated with any radiation will be well and truly around background levels by now.
    I have a couple myself somewhere.

    ALL New lead is already slightly more contaminated by radiation than lead that was produced more than 71 years ago.
    The contamination comes from atmospheric testing of nuclear weapons plus what hospitals release into sewage, which has slightly raised the back ground all around the world including inside any lead that was made after then.
    It's nothing to worry about in terms of health but becomes a PITA for ultra low level radiation measurements since lead is used extensively as shielding and the contamination interferes with these types of measurements.
    The best lead is thus that made before the first nuclear explosion in 1945. A good source of this is old ships that were made before that time that used lead ballast. The price for this lead is significantly greater than the regular price for salvaged lead.

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    Thanks for the info and I wish I had taken some now. I think they will already be recycled but next time I'll know.
    That's pretty interesting on the lead after 1945. If its not too much writing, would you mind trying to explain to a dummy how lead made now is contaminated? I take it the lead atoms are the same, so do you mean that by melting it into a new structure, it will now inevitably collect some radioactive partials similar to getting dust, where an old solid bit of lead is obviously not going to get any dust inside it? Does that mean you can't melt old lead into useful shapes though? Sorry, I'm sure I'm really showing my ignorance now.

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    BobL is offline Member: Blue and white apron brigade
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    Quote Originally Posted by sossity View Post
    Thanks for the info and I wish I had taken some now. I think they will already be recycled but next time I'll know.
    That's pretty interesting on the lead after 1945. If its not too much writing, would you mind trying to explain to a dummy how lead made now is contaminated? I take it the lead atoms are the same, so do you mean that by melting it into a new structure, it will now inevitably collect some radioactive partials similar to getting dust, where an old solid bit of lead is obviously not going to get any dust inside it? Does that mean you can't melt old lead into useful shapes though? Sorry, I'm sure I'm really showing my ignorance now.
    You are correct.

    Nuclear weapons testing and use of radioisotopes by hospitals has very slightly raised the background levels of radiation all over the world. Nuclear weapons testing had the greatest effect because to showered the whole earth with superfine radioactive dust. This dust went everywhere, covering oceans, soils and plants so it ended up in the food chain and inside us which is why atmospheric testing was eventually stopped. However, anyone that grew up in the 50's and 60s' is still slightly more radioactive than persons born before and in more recent times. People born today are not as radioactive and the post WWI generation because the dust has had time to be diluted and some of the most dangerous isotopes (Tritium) has a 12 year half life so it slowly decays away.

    The effect of this is considered small and within the range of the variable background radiation exposures that different persons receive on the earth even before this was a problem. For example people that live on the Perth coastal plain experience about 5 times less background radiation compare to folks who live in the Perth Hills where the natural radioactive background is 5 times higher. People that fly often like pilots or aircraft crew also receive more radiation. The only reason that the nuclear testing contribution to human background radiation was detected was because of the incredibly sensitive and isotope specific detectors that have been available for some time. Like I said above, this is not considered dangerous today but if atmospheric testing had continued it would have become so.

    Now lets get back to the radioactive dust. It goes EVERYWHERE, into every production process. For example, wine bottled after 1945 has more radioactivity in it from the nuclear weapons testing. Not just from the grapes (actually very little comes from inside the grapes) but from the dust that settles on the grapes, the fermentation vats and bottles, the water used to wash the vats and bottles etc. The same happens to lead, the radioactive dust settles on the ore, the freight cars and trucks used to cary the ore, the inside of the smelters, the outside of the ingots, all becoming incorporated into the lead itself.

    Lead is used extensively to shield objects (including humans) from the external background radiation when objects are being tested for radioactivity. Even though lead is good shield, if the lead itself is contaminated with radioactivity the zero or background reading before the object being tested will be higher than desirable. If it is too high the radioactivity from the object being tested will not be detectable within statistics. So lead with the least radioactivity is used.

    When the Fukashima reactor started leaking after the 2011 Japanese tsunami I was able to get some samples of air borne dust from a friend of mine in Tokyo. I sent the friend an aquarium pump connected to an small air filter and he ran the pump for a week drawing air and dust onto the filter which he sent back to Perth. The samples were collected from a playground, a stairwell and various places around his apartment. At work I set students a task of seeing if they could measure ANY radioactivity in the dust. First they had to construct a lead shield or castle round a small chamber big enough to hold the samples (about 100cc). The lead was in the shape of bricks and several hundred kg of lead was used to do this. Then, without any samples inside they had to measure the back ground radiation over one week. From memory they counted something like 700 counts. That's = to 0.001 counts per second which is considered a decent measurement background reading. Most of these counts would have come from the lead bricks and the radiation detector itself.

    The uncertainty or error of any count is the square root of the count so the uncertainty was +/- 26 counts per week, so the background measurement is somewhere between 700 +26 = 726 and 700 -26 =674 counts per week. They had to do this several times with 3 different radiation detectors to get consistent results.

    Then they placed each sample inside the chamber and counted for a week again. The values they obtained could not be distinguished from the back ground measurements. This does not mean there was zero radioactivity from Fukashima in the dust but it could just not be detected above the measurement background. This method is far from the most sensitive methods available which focus on radiation detection from specific isotopes which has clearly shown that the radiation at very low levels had spread as far as the USA.

    Of course you can melt old lead into any shape you wish but once melted it is contaminated and is not as good for use as radiation shielding of sensitive experiments.

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    This might be well off topic by now, but I hope the original question was of interest to fellow scrap hunters.

    I have some info about Chernobyl that might interest you and might affect your findings even. This is all unsubstantiated so perhaps take it with a grain of salt. I'm old enough to know you can't even trust family, but my dad is gone now and he never did anything to make me doubt his word. Most if this comes from what he told me.
    After the Chernobyl accident, the upper atmosphere seems to have gone over the Atlantic and got caught up in the prevalent system of atmospheric lows coming across the Atlantic which drop lots of rain on Scotland, where I lived at the time. My father was involved in making sure food supplies were safe (he was fairly senior in MAFF). Milk was taken off the market at the time because of the levels measured, but as my dad said, what about all the lamb and beef that will be frozen, it will be appearing for years. Meat was never banned. He said he had seen reports regarding the radioactivity measured around Scotland and the levels were high enough to ban milk for a month or so (can't remember exactly), but there were some puddles that were positively dangerous. I imagine the ban was more to make it look like everything was under control, because as you say the half life of some of these things is pretty long. I was interested you said one of the worst culprits had a half life of just 12 years. Isn't plutonium so much of a problem then, because I am sure its much longer half life?

    What might be of interest was that the distribution was far from even and you had to be careful where you took measurments before making a judgement. He said it was very localised, and one puddle could be very high and the next not so bad. I always wondered did that simply mean the contamination was not even distributed for some reason and was clumping in places, or did it mean that there was one particularly nasty radioactive particle in the puddle. The nasty ones might still have been even spread but but just very thinly spread.

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    BobL is offline Member: Blue and white apron brigade
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    Quote Originally Posted by sossity View Post
    What might be of interest was that the distribution was far from even and you had to be careful where you took measurments before making a judgement. He said it was very localised, and one puddle could be very high and the next not so bad. I always wondered did that simply mean the contamination was not even distributed for some reason and was clumping in places, or did it mean that there was one particularly nasty radioactive particle in the puddle. The nasty ones might still have been even spread but but just very thinly spread.

    I agree, the only way that can be tackled is with multiple samples across a area. We only had the time to measure 7 samples as we only had 8 radiation counters and we were doing them as fast as time allowed. Even then the experiment took almost the entire semester to complete. One particle will rarely make a difference and initially where there is one there are usually others until they get so diluted they will blend into the background.

    Not all isotopes enter living things in the same way or reside to the same extent.
    With regards the milk that one is especially important because it is where much of our calcium comes from. Radioactive fall out contains Strontium 90 which is a Calcium equivalent and concentrates and stays in human bones. Most of the radioactive fall out will drop out over a relatively short period of time so for some months the levels may be high which warrants the milk being disposed off. The isotopes that concentrate in muscle are different and relatively short lived so that is probably why they didn't bother with that.

    The long half life of Pu is a hindrance and a small blessing because that means it is not that active and it is an alpha emitter so you have to inhale or digest it to be affected. The short half-life materials are the ones that pose the most immediate danger because they are much more active. U-235 and U-238 are much longer lived than Pu-239 and we are literally living with U every where. If you live in a brick house a significant proportion of your back ground comes from the U in the back clay.

    What I find amazing is that around 30% of smokers die from radiation induced illnesses yet the same people are often paranoid about radiation. The tobacco manufacturers knew all about this in the 1960s and even tried to breed genetically altered tobacco plants that would not take up radioactive dust on their leaves. They failed but told no one.

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    Thanks to the moderators for moving the thread. I though initially it was relevant to metalworking to know if lead containers you might find in a scrap yard were safe, but I took this way off course, sorry. Thanks to Bob, I really appreciate what you wrote, very interesting.
    I can understand people being paranoid about radiation though. Fear of the unknown I suppose. I was of the opinion it would be easy to end up with some kind of isotope inside you, constantly shaking the dice on your cells, in the risk of eventual giving you cancer. From what you say there, it sounds that while its possible in the case of Scotland, its by no means certain this could happen (if like me you like to get into the highlands where the worst radiation was). Hopefully unlikely even.
    I didn’t know that about cigarettes causing problems that way and I bet most smokers don' know.
    I got interested in repairing watches a few years ago. Its widely known to be careful of watches from early 1900s because of the radioactive paint they used. If you are repairing them, the paint turns to dust and you could easily breathe it in. I think everyone has heard about the girls who painted the dials with radium paint. They were told it was harmless and they would lick the end of the brush to bring it to a point and so they ingested the radium. What I read more recently was while a lot of them died of cancers all over in the first year, there was quite a recurrence of cancer in people lucky up until a few years later, particularly brain cancer. The thing I read had the theory that the radium decays into radon gas which found its way in the body to collect in the sinuses. No idea if that’s true but it makes a good (bad) story. The Japanese disaster created a mass market for relatively cheap radiation meters (I think about $200) which is good for people who want to repair old watches. I just stick to later ones.
    I used to provide certification on microwave antenna installations regarding radiation levels. This is non-ionising radiation so a complete change of subject really, but I found it crazy that mums will protest about a cell tower near a school, which gives quite low levels of rf radiation, but the same people will stick a cellphone right up to their brain (and their kids) and expose themselves to way more radiation. Again, I guess it just ignorance, plus a big tower looks nasty and phones look cute and cuddly. Unlike ionising radiation, safe RF radiation limits are purely based on your body’s ability to dissipate heat, particularly your eyes which are full of water that does not circulate and can’t dissipate heat easily. No account is made for the fact that your molecules may be vibrated several billion times a second, and what effect that has. I don’t think anyone knows. I believe there is still no proof that rf radiation can cause cancer, but ask most RF engineers and they will only say that if it worries you, don’t use cellphones.
    Perhaps a similar story to your one about cigarettes is that small microwave antennas are usually much more dangerous that huge ones. Yet people seem to not care about standing in front of a small one, but they will keep away from big ones. Cigarettes are small too, must be safe.

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