Measuring contamination in biological samples - Tables 1 and 3

[Ryan]

I saw some questions in another thread, so I thought I'd also provide some explanation from the radiological report (pp. 371-377) on the biological samples.

First, some background:

Being in the presence of radioactive sources results in an external dose.

For alpha radiation, that dose is zero. Alpha particles are stopped by the dead layer of skin covering our bodies, so they won't damage any living cells.

Beta radiation typically will get absorbed in the skin. It typically cannot penetrate very far. It is possible to get a "beta burn". High doses of beta to the eye can also harm one's vision. (And the beta contamination on the hikers' clothing is many orders of magnitude lower than what would be needed to cause any of this.)

Gamma radiation is typically what one considers when one looks at external dose because it causes the most health risk. Gamma can penetrate deep into the body and damage cells in organs.

With external dose, once you leave the area, the dose stops accumulating.

Internal dose is different. This refers to contamination that gets inside the body. Typically, this happens either through breathing contamination into one's lungs, or eating or drinking something that is contaminated. In this case, the contamination is a gift that keeps on giving. It stays in your body, even when you leave the contaminated environment.

Alpha emitters can cause lots of damage to living lung tissue. This is why radon exposure is the second leading cause of lung cancer.

Sr-90 is particularly dangerous because strontium is chemically similar to calcium. It incorporates in your bones and will irradiate the marrow with beta radiation. Sr-90 released in atmospheric nuclear tests found its way into milk that people drank. It then showed up in children's baby teeth.

Cs-137 and Cs-134 (a shorter half-life fission product) chemically resemble potassium to the body. They accumulates in muscles and organs. Cs-137 is a gamma and beta emitter.

Iodine-131 is a fission product with a very short half life (8 days) that accumulates in the thyroid. A lot of thyroid cancers occurred after Chernobyl.

On my Chernobyl trips, we had dosimeters to monitor external gamma dose. But that was never really much to be alarmed about. The key concern was preventing internal contamination. This means being very mindful of hygiene. Washing hands before eating. Scanning clothing and shoes to make sure contaminated dust doesn't follow you home. When we went inside the Sarcophagus, we were given a full change of clothing, boots, a cap for our hair, gloves, and a dust mask. All this was left behind as we changed back into our own clothes, and we had to pass additional contamination scans to leave.

In addition to analyzing the clothing of the four hikers from the ravine, samples from their bodies were tested as well.

Beta is easily absorbed by tissue and bone. This actually presents a problem when attempting to measure contamination that is distributed throughout a piece of tissue. The betas emitted by contamination close to the center can get absorbed before they can escape to the outside of the sample. Betas originating closer to the outside of the sample have a higher likelihood of escaping and being measured. This is known as self-shielding, causing the sample to appear much less radioactive than it actually is.

The solution here is to burn the sample to ash and then measure the ash. This eliminates all the water and much of the mass, however all the heavier radioactive isotopes should still be left behind in the ash. If we look at Table 1 Row 3, a 42.820 g sample of Kolevatov's brain was burned to produce 0.710 g of ash. Of that ash, 0.2 g was counted in the detector. This small amount is unlikely to self-shield, so it should give a much more accurate result.

This is definitely a different type of detector. It's listed in the report as a BFA-25, also in a "lead house" to reduce background. I have not been able to find any info on what this is. But the conversion factor and background radiation numbers are very different from the detector used to measure the clothing, so I don't think they are the same.

The background radiation for the detector ranges from 22-34 counts per minute in table 1. It appears the background was measured either before or after counting each sample. For line 3, background is 26, and the sample of brain tissue was 4 counts per minute over the background.

Now if 0.2 g of ash were measured out of 0.710 g of ash total, the sample should be (0.710 / 0.2) * 4 = 14.2 counts per minute.

The detector isn't counting every beta. The conversion ratio is 5.5. So the sample is really emitting 14.2 * 5.5 = 78.1 betas per minute.

Because the samples are all variable sizes, one needs to standardize the activity as counts per minute per kilogram. We know that the original brain sample, before burning, was 42.820 g. So the actual sample activity is 78.1 * (1000 / 42.820) = 1824 cpm / kg. The table rounds it to 1850.

1 Curie = 3.7e10 Bequerel. And 1 Bq = 1 count / second. So to convert this to Ci/kg, we take 1824 / (60 * 3.7e10) = 8.2e-10 or 0.82e-9 or 0.82 nCi/kg. The table lists 0.85e-9.

One thing I'd like to note: the activity levels range from 2 to 7 cpm above background. And, as I said, background fluctuates from 22-34 cpm. So many of these measurements are very close to background. A number of rows do not have anything listed; my guess is that 1 cpm or less above background was considered no activity. A small discrepancy in cpm above background translates into a much larger activity.

Table 3 shows the results, for comparison, from a motor vehicle accident victim from Sverdlovsk. In this table, a single background number is used for all samples.

The report concludes that: "Thus, the results of the studies in Tables 1 and 3 do not exceed the averaged data on the content of radioactive substances in human organs and may be due to natural radioactive Potassium-40." I think this makes sense. The most radioactive sample was Kolevatov's heart, at 3.8 nCi/kg, which is very close to the control sample, at 3.6 nCi/kg. So while some of the hikers' bone and tissue samples were above background, none of them were abnormally above background.

What does this say about what happened?

Well, I don't see any discrepancy between the clothes being contaminated and their bodies being normal. In order for the bodies to be contaminated internally, they would first need to be exposed to radioactive contamination, and then it would need a way to enter their bodies.

I think Sr-90 is an excellent candidate for the contamination. But someone getting Sr-90 dumped on them shortly before they died probably won't be internally contaminated. It would need to get inside them (e.g. from the contamination getting into their food) and then I am guessing their body would need time to incorporate the Sr-90 into bone and other cells.

I also saw a question in another thread about why their thyroids were not analyzed for I-131. This would not be possible. Even if they were exposed and there was time for I-131 to enter their bodies and be absorbed by their thyroids before they died, the half life of I-131 is only 8 days. If we assume they died on Feb 2 and were found on May 5, more than 11 half-lives would have passed. Less than 0.05% of the I-131 would be left.

The one issue I have with the biological testing is that no lung tissue of any of the hikers was analyzed. But lung tissue of the Sverdlovsk motor vehicle accident victim was analyzed. This is one place where I think internal exposure may have been possible. If the hikers' lungs were substantially more radioactive than the lungs of the control sample, that might be an indication that they were alive and breathing when they encountered radioactive dust. That said, tobacco contains radon daughters Pb-210 and Po-210 that are absorbed in the lungs. So the amount that someone smoked may also influence how much beta their lung tissue emits.

[Star man]

I saw some questions in another thread, so I thought I'd also provide some explanation from the radiological report (pp. 371-377) on the biological samples.

First, some background:

Being in the presence of radioactive sources results in an external dose.

For alpha radiation, that dose is zero. Alpha particles are stopped by the dead layer of skin covering our bodies, so they won't damage any living cells.

Beta radiation typically will get absorbed in the skin. It typically cannot penetrate very far. It is possible to get a "beta burn". High doses of beta to the eye can also harm one's vision. (And the beta contamination on the hikers' clothing is many orders of magnitude lower than what would be needed to cause any of this.)

Gamma radiation is typically what one considers when one looks at external dose because it causes the most health risk. Gamma can penetrate deep into the body and damage cells in organs.

With external dose, once you leave the area, the dose stops accumulating.

Internal dose is different. This refers to contamination that gets inside the body. Typically, this happens either through breathing contamination into one's lungs, or eating or drinking something that is contaminated. In this case, the contamination is a gift that keeps on giving. It stays in your body, even when you leave the contaminated environment.

Alpha emitters can cause lots of damage to living lung tissue. This is why radon exposure is the second leading cause of lung cancer.

Sr-90 is particularly dangerous because strontium is chemically similar to calcium. It incorporates in your bones and will irradiate the marrow with beta radiation. Sr-90 released in atmospheric nuclear tests found its way into milk that people drank. It then showed up in children's baby teeth.

Cs-137 and Cs-134 (a shorter half-life fission product) chemically resemble potassium to the body. They accumulates in muscles and organs. Cs-137 is a gamma and beta emitter.

Iodine-131 is a fission product with a very short half life (8 days) that accumulates in the thyroid. A lot of thyroid cancers occurred after Chernobyl.

On my Chernobyl trips, we had dosimeters to monitor external gamma dose. But that was never really much to be alarmed about. The key concern was preventing internal contamination. This means being very mindful of hygiene. Washing hands before eating. Scanning clothing and shoes to make sure contaminated dust doesn't follow you home. When we went inside the Sarcophagus, we were given a full change of clothing, boots, a cap for our hair, gloves, and a dust mask. All this was left behind as we changed back into our own clothes, and we had to pass additional contamination scans to leave.

In addition to analyzing the clothing of the four hikers from the ravine, samples from their bodies were tested as well.

Beta is easily absorbed by tissue and bone. This actually presents a problem when attempting to measure contamination that is distributed throughout a piece of tissue. The betas emitted by contamination close to the center can get absorbed before they can escape to the outside of the sample. Betas originating closer to the outside of the sample have a higher likelihood of escaping and being measured. This is known as self-shielding, causing the sample to appear much less radioactive than it actually is.

The solution here is to burn the sample to ash and then measure the ash. This eliminates all the water and much of the mass, however all the heavier radioactive isotopes should still be left behind in the ash. If we look at Table 1 Row 3, a 42.820 g sample of Kolevatov's brain was burned to produce 0.710 g of ash. Of that ash, 0.2 g was counted in the detector. This small amount is unlikely to self-shield, so it should give a much more accurate result.

This is definitely a different type of detector. It's listed in the report as a BFA-25, also in a "lead house" to reduce background. I have not been able to find any info on what this is. But the conversion factor and background radiation numbers are very different from the detector used to measure the clothing, so I don't think they are the same.

The background radiation for the detector ranges from 22-34 counts per minute in table 1. It appears the background was measured either before or after counting each sample. For line 3, background is 26, and the sample of brain tissue was 4 counts per minute over the background.

Now if 0.2 g of ash were measured out of 0.710 g of ash total, the sample should be (0.710 / 0.2) * 4 = 14.2 counts per minute.

The detector isn't counting every beta. The conversion ratio is 5.5. So the sample is really emitting 14.2 * 5.5 = 78.1 betas per minute.

Because the samples are all variable sizes, one needs to standardize the activity as counts per minute per kilogram. We know that the original brain sample, before burning, was 42.820 g. So the actual sample activity is 78.1 * (1000 / 42.820) = 1824 cpm / kg. The table rounds it to 1850.

1 Curie = 3.7e10 Bequerel. And 1 Bq = 1 count / second. So to convert this to Ci/kg, we take 1824 / (60 * 3.7e10) = 8.2e-10 or 0.82e-9 or 0.82 nCi/kg. The table lists 0.85e-9.

One thing I'd like to note: the activity levels range from 2 to 7 cpm above background. And, as I said, background fluctuates from 22-34 cpm. So many of these measurements are very close to background. A number of rows do not have anything listed; my guess is that 1 cpm or less above background was considered no activity. A small discrepancy in cpm above background translates into a much larger activity.

Table 3 shows the results, for comparison, from a motor vehicle accident victim from Sverdlovsk. In this table, a single background number is used for all samples.

The report concludes that: "Thus, the results of the studies in Tables 1 and 3 do not exceed the averaged data on the content of radioactive substances in human organs and may be due to natural radioactive Potassium-40." I think this makes sense. The most radioactive sample was Kolevatov's heart, at 3.8 nCi/kg, which is very close to the control sample, at 3.6 nCi/kg. So while some of the hikers' bone and tissue samples were above background, none of them were abnormally above background.

What does this say about what happened?

Well, I don't see any discrepancy between the clothes being contaminated and their bodies being normal. In order for the bodies to be contaminated internally, they would first need to be exposed to radioactive contamination, and then it would need a way to enter their bodies.

I think Sr-90 is an excellent candidate for the contamination. But someone getting Sr-90 dumped on them shortly before they died probably won't be internally contaminated. It would need to get inside them (e.g. from the contamination getting into their food) and then I am guessing their body would need time to incorporate the Sr-90 into bone and other cells.

I also saw a question in another thread about why their thyroids were not analyzed for I-131. This would not be possible. Even if they were exposed and there was time for I-131 to enter their bodies and be absorbed by their thyroids before they died, the half life of I-131 is only 8 days. If we assume they died on Feb 2 and were found on May 5, more than 11 half-lives would have passed. Less than 0.05% of the I-131 would be left.

The one issue I have with the biological testing is that no lung tissue of any of the hikers was analyzed. But lung tissue of the Sverdlovsk motor vehicle accident victim was analyzed. This is one place where I think internal exposure may have been possible. If the hikers' lungs were substantially more radioactive than the lungs of the control sample, that might be an indication that they were alive and breathing when they encountered radioactive dust. That said, tobacco contains radon daughters Pb-210 and Po-210 that are absorbed in the lungs. So the amount that someone smoked may also influence how much beta their lung tissue emits.

Thanks for this Ryan.  I think it is very useful information.  So from what you are saying it seems that if they were contaminated with materials shortly before they died, then we would:

1. Expect to see the results of increased contamination on the clothing, and outside of the bodies.  Which appears to be what has been concluded.

2.  We would not expect to see significant increase in internal contamination of body tissues expect for maybe the lungs,  and analysis concludes that there is no significant increase in tissue contamination, the lungs have not been analysed - as far as we know so no result there.

3.  Iodine in thyroids is not a good indicator due to the length of time that has elapsed.

Overall conclusion given available information:

It looks as if there was some kind of external contamination, and it's likely that strontium 90 is one of the main components of this contamination.

Strontium 90 would still be present in the tree rings around the area if there was widespread contamination, albeit subject to decay of 2 half lives, leaving only 25% of the original concentration.  Strontium 90 is not mobile in the tree rings so would be able to tell from this if and when there was a spike in the local environment.

If the contamination was a result of nuclear fission, then there should also be caesium 137 in the tree rings at higher concentration than normal background, but this would be more spread out across the rings, due to its greater solubility/mobility.

Question: Given the bodies in the ravine were there for over 3 months, how much of the original contamination could have been rinsed away?  And if it was what would be the estimate of the original levels of contamination?


By the way didn't realise that you had actually been in Chernobyl.  Must have been very interesting?

[sarapuk]

I saw some questions in another thread, so I thought I'd also provide some explanation from the radiological report (pp. 371-377) on the biological samples.

First, some background:

Being in the presence of radioactive sources results in an external dose.

For alpha radiation, that dose is zero. Alpha particles are stopped by the dead layer of skin covering our bodies, so they won't damage any living cells.

Beta radiation typically will get absorbed in the skin. It typically cannot penetrate very far. It is possible to get a "beta burn". High doses of beta to the eye can also harm one's vision. (And the beta contamination on the hikers' clothing is many orders of magnitude lower than what would be needed to cause any of this.)

Gamma radiation is typically what one considers when one looks at external dose because it causes the most health risk. Gamma can penetrate deep into the body and damage cells in organs.

With external dose, once you leave the area, the dose stops accumulating.

Internal dose is different. This refers to contamination that gets inside the body. Typically, this happens either through breathing contamination into one's lungs, or eating or drinking something that is contaminated. In this case, the contamination is a gift that keeps on giving. It stays in your body, even when you leave the contaminated environment.

Alpha emitters can cause lots of damage to living lung tissue. This is why radon exposure is the second leading cause of lung cancer.

Sr-90 is particularly dangerous because strontium is chemically similar to calcium. It incorporates in your bones and will irradiate the marrow with beta radiation. Sr-90 released in atmospheric nuclear tests found its way into milk that people drank. It then showed up in children's baby teeth.

Cs-137 and Cs-134 (a shorter half-life fission product) chemically resemble potassium to the body. They accumulates in muscles and organs. Cs-137 is a gamma and beta emitter.

Iodine-131 is a fission product with a very short half life (8 days) that accumulates in the thyroid. A lot of thyroid cancers occurred after Chernobyl.

On my Chernobyl trips, we had dosimeters to monitor external gamma dose. But that was never really much to be alarmed about. The key concern was preventing internal contamination. This means being very mindful of hygiene. Washing hands before eating. Scanning clothing and shoes to make sure contaminated dust doesn't follow you home. When we went inside the Sarcophagus, we were given a full change of clothing, boots, a cap for our hair, gloves, and a dust mask. All this was left behind as we changed back into our own clothes, and we had to pass additional contamination scans to leave.

In addition to analyzing the clothing of the four hikers from the ravine, samples from their bodies were tested as well.

Beta is easily absorbed by tissue and bone. This actually presents a problem when attempting to measure contamination that is distributed throughout a piece of tissue. The betas emitted by contamination close to the center can get absorbed before they can escape to the outside of the sample. Betas originating closer to the outside of the sample have a higher likelihood of escaping and being measured. This is known as self-shielding, causing the sample to appear much less radioactive than it actually is.

The solution here is to burn the sample to ash and then measure the ash. This eliminates all the water and much of the mass, however all the heavier radioactive isotopes should still be left behind in the ash. If we look at Table 1 Row 3, a 42.820 g sample of Kolevatov's brain was burned to produce 0.710 g of ash. Of that ash, 0.2 g was counted in the detector. This small amount is unlikely to self-shield, so it should give a much more accurate result.

This is definitely a different type of detector. It's listed in the report as a BFA-25, also in a "lead house" to reduce background. I have not been able to find any info on what this is. But the conversion factor and background radiation numbers are very different from the detector used to measure the clothing, so I don't think they are the same.

The background radiation for the detector ranges from 22-34 counts per minute in table 1. It appears the background was measured either before or after counting each sample. For line 3, background is 26, and the sample of brain tissue was 4 counts per minute over the background.

Now if 0.2 g of ash were measured out of 0.710 g of ash total, the sample should be (0.710 / 0.2) * 4 = 14.2 counts per minute.

The detector isn't counting every beta. The conversion ratio is 5.5. So the sample is really emitting 14.2 * 5.5 = 78.1 betas per minute.

Because the samples are all variable sizes, one needs to standardize the activity as counts per minute per kilogram. We know that the original brain sample, before burning, was 42.820 g. So the actual sample activity is 78.1 * (1000 / 42.820) = 1824 cpm / kg. The table rounds it to 1850.

1 Curie = 3.7e10 Bequerel. And 1 Bq = 1 count / second. So to convert this to Ci/kg, we take 1824 / (60 * 3.7e10) = 8.2e-10 or 0.82e-9 or 0.82 nCi/kg. The table lists 0.85e-9.

One thing I'd like to note: the activity levels range from 2 to 7 cpm above background. And, as I said, background fluctuates from 22-34 cpm. So many of these measurements are very close to background. A number of rows do not have anything listed; my guess is that 1 cpm or less above background was considered no activity. A small discrepancy in cpm above background translates into a much larger activity.

Table 3 shows the results, for comparison, from a motor vehicle accident victim from Sverdlovsk. In this table, a single background number is used for all samples.

The report concludes that: "Thus, the results of the studies in Tables 1 and 3 do not exceed the averaged data on the content of radioactive substances in human organs and may be due to natural radioactive Potassium-40." I think this makes sense. The most radioactive sample was Kolevatov's heart, at 3.8 nCi/kg, which is very close to the control sample, at 3.6 nCi/kg. So while some of the hikers' bone and tissue samples were above background, none of them were abnormally above background.

What does this say about what happened?

Well, I don't see any discrepancy between the clothes being contaminated and their bodies being normal. In order for the bodies to be contaminated internally, they would first need to be exposed to radioactive contamination, and then it would need a way to enter their bodies.

I think Sr-90 is an excellent candidate for the contamination. But someone getting Sr-90 dumped on them shortly before they died probably won't be internally contaminated. It would need to get inside them (e.g. from the contamination getting into their food) and then I am guessing their body would need time to incorporate the Sr-90 into bone and other cells.

I also saw a question in another thread about why their thyroids were not analyzed for I-131. This would not be possible. Even if they were exposed and there was time for I-131 to enter their bodies and be absorbed by their thyroids before they died, the half life of I-131 is only 8 days. If we assume they died on Feb 2 and were found on May 5, more than 11 half-lives would have passed. Less than 0.05% of the I-131 would be left.

The one issue I have with the biological testing is that no lung tissue of any of the hikers was analyzed. But lung tissue of the Sverdlovsk motor vehicle accident victim was analyzed. This is one place where I think internal exposure may have been possible. If the hikers' lungs were substantially more radioactive than the lungs of the control sample, that might be an indication that they were alive and breathing when they encountered radioactive dust. That said, tobacco contains radon daughters Pb-210 and Po-210 that are absorbed in the lungs. So the amount that someone smoked may also influence how much beta their lung tissue emits.

Very good and informative.  Only 4 bodies were tested, and only some parts of those bodies.  And they were the ones from the Ravine. Some people have suggested that contaminated water from the stream was the source of the Radiation. But apparently at least one Geiger Counter recorded High Radiation Levels around the Tent.  But of course this is Missing Information.  It certainly looks like the Lab Staff carried out the correct procedure for Testing for Radiation Particles. But they didnt Test some parts of the bodies that one would have thought was usual practice in searching for signs of Radiation ! ?

[Kasey00]

I saw some questions in another thread, so I thought I'd also provide some explanation from the radiological report (pp. 371-377) on the biological samples.

First, some background:

Being in the presence of radioactive sources results in an external dose.

For alpha radiation, that dose is zero. Alpha particles are stopped by the dead layer of skin covering our bodies, so they won't damage any living cells.

Beta radiation typically will get absorbed in the skin. It typically cannot penetrate very far. It is possible to get a "beta burn". High doses of beta to the eye can also harm one's vision. (And the beta contamination on the hikers' clothing is many orders of magnitude lower than what would be needed to cause any of this.)

Gamma radiation hostgator is typically what one considers when one looks at external dose because it causes the most health risk. Gamma can penetrate deep into the body and damage cells in organs.

With external dose, once you leave the area, the dose stops accumulating.

Internal dose is different. This refers to contamination that gets inside the body. Typically, this happens either through breathing contamination into one's lungs, or eating or drinking something that is contaminated. In this case, the contamination is a gift that keeps on giving. It stays in your body, even when you leave the contaminated environment.

Alpha emitters can cause lots of damage to living lung tissue. This is why radon exposure is the second leading cause of lung cancer.

Sr-90 is particularly dangerous because strontium is chemically similar to calcium. It incorporates in your bones and will irradiate the marrow with beta radiation. Sr-90 released in atmospheric nuclear tests found its way into milk that people drank. It then showed up in children's baby teeth.

Cs-137 and Cs-134 (a shorter half-life fission product) chemically resemble potassium to the body. They accumulates in muscles and organs. Cs-137 is a gamma and beta emitter.

Iodine-131 is a fission product with a very short half life (8 days) that accumulates in the thyroid. A lot of thyroid cancers occurred after Chernobyl.

On my Chernobyl trips, we had dosimeters to monitor external gamma dose. But that was never really much to be alarmed about. The key concern was preventing internal contamination. This means being very mindful of hygiene. Washing hands before eating. Scanning clothing and shoes to make sure contaminated dust doesn't follow you home. When we went inside the Sarcophagus, we were given a full change of clothing, boots, a cap for our hair, gloves, and a dust mask. All this was left behind as we changed back into our own clothes, and we had to pass additional contamination scans to leave.

In addition to analyzing the clothing of the four hikers from the ravine, samples from their bodies were tested as well.

Beta smallpdf is easily absorbed by tissue and bone. This actually presents a problem when attempting to measure contamination that is distributed throughout a piece of tissue. The betas emitted by contamination close to the center can get absorbed before they can escape to the outside of the sample. Betas originating closer to the outside of the sample have a higher likelihood of escaping and being measured. This is known as self-shielding, causing the sample to appear much less radioactive than it actually is.

The solution here is to burn the sample to ash and then measure the ash. This eliminates all the water and much of the mass, however all the heavier radioactive isotopes should still be left behind in the ash. If we look at Table 1 Row 3, a 42.820 g sample of Kolevatov's brain was burned to produce 0.710 g of ash. Of that ash, 0.2 g was counted in the detector. This small amount is unlikely to self-shield, so it should give a much more accurate result.

This is definitely a different type of detector. It's listed in the report as a BFA-25, also in a "lead house" to reduce background. I have not been able to find any info on what this is. But the conversion factor and background radiation numbers are very different from the detector used to measure the clothing, so I don't think they are the same.

The background radiation for the detector ranges from 22-34 counts per minute in table 1. It appears the background was measured either before or after counting each sample. For line 3, background is 26, and the sample of brain tissue was 4 counts per minute over the background.

Now if 0.2 g of ash were measured out of 0.710 g of ash total, the sample should be (0.710 / 0.2) * 4 = 14.2 counts per minute.

The detector isn't counting every beta. The conversion ratio is 5.5. So the sample is really emitting 14.2 * 5.5 = 78.1 betas per minute.

Because the samples are all variable sizes, one needs to standardize the activity as counts per minute per kilogram. We know that the original brain sample, before burning, was 42.820 g. So the actual sample activity is 78.1 * (1000 / 42.820) = 1824 cpm / kg. The table rounds it to 1850.

1 Curie = 3.7e10 Bequerel. And 1 Bq = 1 count / second. So to convert this to Ci/kg, we take 1824 / (60 * 3.7e10) = 8.2e-10 or 0.82e-9 or 0.82 nCi/kg. The table lists 0.85e-9.

One thing I'd like to note: the activity levels range from 2 to 7 cpm above background. And, as I said, background fluctuates from 22-34 cpm. So many of these measurements are very close to background. A number of rows do not have anything listed; my guess is that 1 cpm or less above background was considered no activity. A small discrepancy in cpm above background translates into a much larger activity.

Table 3 shows the results, for comparison, from a motor vehicle accident victim from Sverdlovsk. In this table, a single background number is used for all samples.

The report concludes that: "Thus, the results of the studies in Tables 1 and 3 do not exceed the averaged data on the content of radioactive substances in human organs and may be due to natural radioactive Potassium-40." I think this makes sense. The most radioactive sample was Kolevatov's heart, at 3.8 nCi/kg, which is very close to the control sample, at 3.6 nCi/kg. So while some of the hikers' bone and tissue samples were above background, none of them were abnormally above background.

What does this say about what happened?

Well, I don't see any discrepancy between the clothes being contaminated and their bodies being normal. In order for the bodies to be contaminated internally, they would first need to be exposed to radioactive contamination, and then it would need a way to enter their bodies.

I think Sr-90 is an excellent candidate for the contamination. But someone getting Sr-90 dumped on them shortly before they died probably won't be internally contaminated. It would need to get inside them (e.g. from the contamination getting into their food) and then I am guessing their body would need time to incorporate the Sr-90 into bone and other cells.

I also saw a question in another thread about why their thyroids were not analyzed for I-131. This would not be possible. Even if they were exposed and there was time for I-131 to enter their bodies and be absorbed by their thyroids before they died, the half life of I-131 is only 8 days. If we assume they died on Feb 2 and were found on May 5, more than 11 half-lives would have passed. Less than 0.05% of the I-131 would be left.

The one issue I have with the biological testing is that no lung tissue of any of the hikers was analyzed. But lung tissue of the Sverdlovsk motor vehicle accident victim was analyzed. This is one place where I think internal exposure may have been possible. If the hikers' lungs were substantially more radioactive than the lungs of the control sample, that might be an indication that they were alive and breathing when they encountered radioactive dust. That said, tobacco contains radon daughters Pb-210 and Po-210 that are absorbed in the lungs. So the amount that someone smoked may also influence how much beta their lung tissue emits.

We would not expect to see significant increase in internal contamination of body tissues expect for maybe the lungs,  and analysis concludes that there is no significant increase in tissue contamination, the lungs have not been analysed - as far as we know so no result there.

[Jean Daniel Reuss]

I saw some questions in another thread, so I thought I'd also provide some explanation from the radiological report (pp. 371-377) on the biological samples.

First, some background:
Being in the presence of radioactive sources results in an external dose....
......................

We would not expect to see significant increase in internal contamination of body tissues expect for maybe the lungs,  and analysis concludes that there is no significant increase in tissue contamination, the lungs have not been analysed - as far as we know so no result there.

The whole comment is correct but I do not think it would be helpful to find an explanation from the DPI.
That is to say that abandonment of the tent underdressed, bruises or serious injuries...etc. cannot be explained by radioactive contamination, whether this contamination is low, medium, high or very high.
See :
https://en.wikipedia.org/wiki/Acute_radiation_syndrome
https://en.wikipedia.org/wiki/Radioactive_contamination

 • Indeed, in the vicinity of Sverdlosk, during the years 1958-1959, there were many research, studies and production activities involving radioactive elements and some containment failures and radioactive leaks were likely if not inevitable.

 • Moreover, it is reasonable to assume that some of the students at the UPI were normally required to carry out practical exercises with radioactive products during which the maximum precautions according to current standards were not taken. This was the mentality of the time in all laboratories and educational establishments throughout the world.

[Ryan]

• Indeed, in the vicinity of Sverdlosk, during the years 1958-1959, there were many research, studies and production activities involving radioactive elements and some containment failures and radioactive leaks were likely if not inevitable.

Yes, but much of this, like the Mayak accident, was in the form of fission products, which would include Cs-137, a beta and gamma emitter. That no gammas were detected implies either that the contamination was primarily beta-only (which excludes the common mix of nuclear fission products) or, much less likely, that the dosimetrist did not have gamma detection instruments sensitive enough to detect the gamma dose rate accompanying such a small beta dose rate.

• Moreover, it is reasonable to assume that some of the students at the UPI were normally required to carry out practical exercises with radioactive products during which the maximum precautions according to current standards were not taken. This was the mentality of the time in all laboratories and educational establishments throughout the world.

I really have to disagree here. University students aren't going to work with specialized radioisotopes as part of their general education. I might believe this for Kolevatov, as he was studying nuclear physics. But Dubinina was studying engineering and economics. Thibeaux-Brignolle graduated in civil engineering and was working in construction. And Zolotaryov was a tourism instructor who graduated from a Minsk physical education school in 1950.

All four of them were wearing contaminated clothing. Contamination just doesn't randomly spread from one person to another without some specific mechanism, and I don't see how that could happen here.

[Manti]

So may I ask what is it that you are suggesting?

If I understand correctly:
The test of internal tissues was carried out correctly and the conclusion of no significant radiation above background is correct. But there was external contamination and on all the ravine 4 and you don't see how this could have happened?

[Ryan]

So may I ask what is it that you are suggesting?

If I understand correctly:
The test of internal tissues was carried out correctly and the conclusion of no significant radiation above background is correct. But there was external contamination and on all the ravine 4 and you don't see how this could have happened?

There is no contradiction between a lack of radioisotopes above background in a person’s tissues and a presence of radioisotopes well above background on a person’s clothing.

Radioisotopes primarily get into a person’s tissues by eating contaminated food or breathing contaminated air. No lung tissues of any of the hikers was analyzed, so we have no way of knowing if their lungs were contaminated, say, by breathing in radioactive dust. But the lack or activity in tissue and bone is perfectly normal.

Yes, I can’t see an obvious way all four people in the ravine were contaminated by a pure beta emitter. This isn’t something common. Uranium, thorium, and radium don’t qualify. Neither does the mess of fission products produced by a nuclear weapon or a nuclear reactor accident, or a nuclear fuel processing accident like what happened at Chelyabinsk.

Pure beta emitters like Sr-90 are specifically bred inside reactors by neutron irradiation of targets or are separated chemically from spent nuclear fuel. Average people will not possess this. Even radioactive check sources containing Sr-90, used for testing Geiger counters, are going to be embedded in a resin so they don’t pose a contamination risk. So how can four hikers’ clothing get contaminated with something so specific and unusual?

This is why I tend to think the military has to be involved. If, say, they detonated a dirty bomb in a test that dispersed Sr-90, that would be a good way multiple peoples’ clothing would be contaminated with it.

[KFinn]

So may I ask what is it that you are suggesting?

If I understand correctly:
The test of internal tissues was carried out correctly and the conclusion of no significant radiation above background is correct. But there was external contamination and on all the ravine 4 and you don't see how this could have happened?

There is no contradiction between a lack of radioisotopes above background in a person’s tissues and a presence of radioisotopes well above background on a person’s clothing.

Radioisotopes primarily get into a person’s tissues by eating contaminated food or breathing contaminated air. No lung tissues of any of the hikers was analyzed, so we have no way of knowing if their lungs were contaminated, say, by breathing in radioactive dust. But the lack or activity in tissue and bone is perfectly normal.

Yes, I can’t see an obvious way all four people in the ravine were contaminated by a pure beta emitter. This isn’t something common. Uranium, thorium, and radium don’t qualify. Neither does the mess of fission products produced by a nuclear weapon or a nuclear reactor accident, or a nuclear fuel processing accident like what happened at Chelyabinsk.

Pure beta emitters like Sr-90 are specifically bred inside reactors by neutron irradiation of targets or are separated chemically from spent nuclear fuel. Average people will not possess this. Even radioactive check sources containing Sr-90, used for testing Geiger counters, are going to be embedded in a resin so they don’t pose a contamination risk. So how can four hikers’ clothing get contaminated with something so specific and unusual?

This is why I tend to think the military has to be involved. If, say, they detonated a dirty bomb in a test that dispersed Sr-90, that would be a good way multiple peoples’ clothing would be contaminated with it.

I'm not certain I would go so far as to say the Russians have a good history with safe handling of nuclear products.  It wasn't even fifteen years ago when the men who poisoned Litvinenko carried a leaking metal can of polonium around Britain, leaving hotels, airplanes,  restaurants and taxis contaminated before they flushed what was left down a toilet...  Back in 1959, even we Americans weren't all that great with safe handling practices. 

[Ryan]

I don’t doubt that contamination can occur. But that alone doesn’t account for the data. For contamination from industry or the university to account for what we see in the case files, then all of the following need to be true:

1. The person was specifically working with a pure beta emitter like Sr-90 and contaminated their clothing. Fission products, e.g. cleanup after the Kyshtym disaster, would not match with the results from the report.

2. The person managed to bring their contaminated clothing on the hike. Keep in mind that  the clothes worn at work or university may not be suitable to take on a ski expedition.

3. There would need to be a mechanism where the contaminated clothing managed to contaminate 9 different pieces of clothing worn by the 4 hikers found in the ravine.

This is why I think it is largely impossible. Multiple pieces of clothing from one person might be contaminated if they were all washed in the same washing machine, or were all packed together in the same rucksack. But the contaminated clothing didn’t all come from one person.

[Manti]

The argument against military testing of any nuclear device is that a test ban "moratorium" was in effect at the time: https://www.nytimes.com/1986/01/19/opinion/l-the-russians-broke-1958-61-test-moratorium-561586.html


It looks like the Russians broke this initially but then didn't conduct a test between Nov/3. 1958 and Sep/1. 1961.

So that is 4 months since the last test anywhere in the SU at the time of the Dyatlov incident.


I raised this in another thread and actually was convinced it's not the case, but what is your opinion on the scenario that gamma radiation was "not tested" as opposed to being tested but not detected?

Also another thing that I've always wondered about the radiation report is, was relatively high contamination only detected in specific  areas on the clothing, or were these simply random areas that were tested and other parts weren't?

Further investigation allowed maximum contamination to be established on different spots of clothing:

• Brown sweater from №4: 9900 cpm on 150 cm²

Does this mean the contamination was especially high in that 150cm² area? (12 * 12cm, roughly the size of a hand?)
The area is the same on all the clothing, could this hint at the size of the contaminating object? Or am I misinterpreting this?

[Manti]

Seems like I was misinterpreting, all the data is expressed as radiation per 150cm² area.

Anyway are there other plausible contaminants apart from strontium? One thing that maybe be a candidate is tritiated rust which I believe is a welding product (for example could be present on the stove). It has a half-life of 12 years, but it's probably much too weak to account for the contamination.

Here is a complete a list of beta-only emitters: http://homepages.cae.wisc.edu/~blanchar/purebeta.htm I guess those can be excluded that have half-lives too short, or decay products that are alpha/gamma emitters because then gamma radiation would have been detected too, also gases like Kr-85. Still, leaves a lot of possibilities..



Another thought: strontium is not water-soluble, but it is stated that the contamination decreased with washing. Or does solubility not matter if it's in dust form?

[KFinn]

So, most of you seem to have a much firmer grasp on the radiation aspect than I.  It is admittedly not my forte. 

A recent NY Times article that Teddy posted mentioned the belief by some that the altitude and sun could have caused the radiological contamination on the clothes.  My first thought was how  would that even happen if the clothes were under ten feet of snow?  My second thought was that the altitude doesn't seem nearly high enough for that process to happen.  As you all have a better grasp on the science, if we put this on a spectrum of plausibility with the other theories, how plausible is this? 

[Nigel Evans]

So, most of you seem to have a much firmer grasp on the radiation aspect than I.  It is admittedly not my forte. 

A recent NY Times article that Teddy posted mentioned the belief by some that the altitude and sun could have caused the radiological contamination on the clothes.  My first thought was how  would that even happen if the clothes were under ten feet of snow?  My second thought was that the altitude doesn't seem nearly high enough for that process to happen.  As you all have a better grasp on the science, if we put this on a spectrum of plausibility with the other theories, how plausible is this?

Happy to help. This has been discussed in depth by some extremely knowledgable posters in the past (from memory one worked on the casing of Chernobyl).

• Carbon14 is produced naturally high in the atmosphere and then falls slowly to earth to be absorbed by plants, hence it's use in carbon dating. Mountains by forcing air over the top of them might collect more of this C14 than the ground in general (wind eddies, more precipitation). This same mountainous ground will then receive more precipitation/melting creating runoff which will collect and concentrate in streams and gullies. So the mud at the bottom of the same can contain unusually high levels of the beta emitter C14.
• The US tested 200? nuclear warheads in the atmosphere in the 1950s and of course the USSR did similar culminating with the "Tsar Bomba" resulting in worldwide atmospheric contamination which of course was probably collected by mountains more than elsewhere and then the same as above. Plus Russia had disasters of course like Khystym.

So the problem with the radiation evidence is that it doesn't really prove anything on it's own. the isotope was never identified by Ivanov's lab so could be natural, could be man made.... One things for sure the KGB would have known.... Urakov?

[Ryan]

Manti has asked some really good questions about the radiation report. It probably is best to address the test moratorium and non-proliferation geopolitics in another thread.

I raised this in another thread and actually was convinced it's not the case, but what is your opinion on the scenario that gamma radiation was "not tested" as opposed to being tested but not detected?

First off, my Russian is extremely limited, and I don't even try to read the original case files, making do with the translations. Anyone who can read the original Russian and can provide an opinion on the exact phrasing of the original would be appreciated.

From sheet 372:

Samples of solid biosubstrates and clothes combined in groups under Nos 1, 2, 3, 4 were submitted to the radio-isotope laboratory of the Sverdlovsk Sanitary epidemiological station and were analyzed for presence of radioactive materials.
Dosimetric measurements of clothes showed excessive radioactivity (Betaemission only, no Alpha or Gamma-quanta) of 200–300 counts per minute (cpm) over the natural background.

This language implies to me that all were tested, only beta was detected, and alpha and gamma ruled out. Testing only for beta makes no sense when dealing with unknown radioactive material. Geiger counters typically are always sensitive to gammas. Also, gamma is by far the most dangerous type of radiation for external exposure, so failing to test for it makes absolutely no sense.

Thin-wall metal Geiger tubes are sensitive to hard (high energy) betas and gammas. A quick way to categorize radiation is to use such a counter, measure the sample (collecting beta + gamma), then insert a metal shield between the Geiger tube and the sample, and test again. Gamma radiation would largely pass through thin metal, while beta radiation would be almost completely blocked.

Gamma can also be detected via a scintillator, such as NaI(Tl), which is a very sensitive method of detection. Alpha can be detected by specialized Geiger tubes that have thin mica windows, which would be sensitive to alpha, beta, and gamma. A sheet of paper can shield alphas, so a drop in count rate after introducing a sheet of paper indicates their presence. Alphas can also be detected via a ZnS scintillator, which has the benefit of being sensitive almost exclusively to alpha and almost completely insensitive to beta and gamma, so there would be no need to shield and subtract.

We don't know what equipment was used, but I don't believe that language would have been used if some test for each of alpha, beta, and gamma was made and the lab technician had not ruled the other two out.

Both alpha scintillators and mica window Geiger tubes are very sensitive to alpha. If this were natural uranium or thorium (say, from a lantern mantle) then detecting it would be trivial.

Gamma is a different matter. We don't know how gamma was ruled out. As I've mentioned elsewhere, fission products contain, among other things, a mix of Cs-137 and Sr-90, which collectively emit a lot of gamma and beta. Thin-wall metal Geiger tubes are not terribly sensitive to gamma. So it is possible that, for a low enough activity sample of fission products, beta would be above the threshold for detection and gamma would be below it. For 200-300 cpm beta above background, this is an interesting question, which is why I can't completely rule out fission products. If I knew they tested for gamma with a NaI(Tl) scintillator, the gamma level of detection would be low enough that there is no question the gammas from fission products having 200-300 cpm beta could be detected, and I would definitely rule out fission products. They also have a "lead castle" to lower background. Taking a measurement in such a lead castle with a shielded Geiger tube would be more likely to reveal gammas from fission, if they were there, than simply waving a shielded Geiger probe over a low gamma activity sample and simply listening for differences in cpm by ear.

To this end, I would say that an alpha emitter like U or Th can be ruled out, a hard beta emitter like Sr-90 is definitely possible, and the blend of fission products that includes Cs-137 and Sr-90 may or may not be ruled out depending on the equipment used.

Also another thing that I've always wondered about the radiation report is, was relatively high contamination only detected in specific  areas on the clothing, or were these simply random areas that were tested and other parts weren't?

That's a very good question, and the answer is that we don't know. This is a question of sampling bias. All 9 samples were well above background, and several were above Soviet nuclear worker occupational limits. The real question is whether the 9 samples of clothing were picked without bias, or whether some "cherry picking" happened, e.g. all the clothing was frisked with a Geiger counter and only the hottest parts were analyzed.

Ivanov's resolution for testing, in case files sheet 370, states:

At the disposal of the expert to present all the clothes of Zolotaryov, Dubinina, Kolevatov and Thibeaux-Brignolle, as well as part of their bodies.

I interpret this to mean that the Sverdlovsk lab had all of the clothing of the four hikers in the ravine. The lab definitely has Geiger counters, so they could have done a preliminary scan and intentionally picked 9 definitely hot pieces of the clothing to work with. They also could have taken pieces at random. Unfortunately, we don't know.

Still, even with sampling bias, it can be said that all four hikers wore at least one piece of clothing contaminated significantly above background, which is not what one would ever expect from natural sources and global atmospheric nuclear testing.

You're right; radiation count rates are normalized to counts per 150 cm^2 to account for differences in sizes of samples.

Anyway are there other plausible contaminants apart from strontium? One thing that maybe be a candidate is tritiated rust which I believe is a welding product (for example could be present on the stove). It has a half-life of 12 years, but it's probably much too weak to account for the contamination.

Here is a complete a list of beta-only emitters: http://homepages.cae.wisc.edu/~blanchar/purebeta.htm I guess those can be excluded that have half-lives too short, or decay products that are alpha/gamma emitters because then gamma radiation would have been detected too, also gases like Kr-85. Still, leaves a lot of possibilities..

Another thought: strontium is not water-soluble, but it is stated that the contamination decreased with washing. Or does solubility not matter if it's in dust form?

The contaminant does NOT have to be Sr-90. I mention it because it is an easily obtained and measured hard beta emitter. It is produced in significant quantity in nuclear fission. Later period Soviet Geiger counters include a small amount of Sr-90, safely embedded in epoxy resin, as an operational check and calibration source.

However, we know from the report that the quantitative testing on clothing was done with STS-6 Geiger tubes. These can still be purchased, and data sheets are available. These are thin-walled hard beta and gamma sensitive tubes. Sr-90 can easily be detected with such tubes. But Sr-90 has a maximum and average beta energy of 546 and 196 keV, respectively. This is enough to get through the thin metal wall of the STS-6 Geiger tube and register a count. Tritiated rust can be ruled out, as the max and avg energy is 18.6 and 5.7 keV. Even C-14 (max/avg 157/50 keV) is probably too soft to be counted on an STS-6. Something like P-32 is plenty energetic, but with a half-life of 14 days, it would be gone by the time the bodies were discovered (assuming exposure was approximately concurrent with death.) So the list of suspects can be limited.

The question of solubility is a good one. Insoluble particles can be trapped in the cloth fibers. Running water through or over the cloth can mechanically dislodge and carry away particles. So something insoluble in water like Sr would tend to remain in the clothing unless the mechanical action of the water washed the particles out. I definitely would expect washing in running water to reduce the activity on the cloth samples.

[Ryan]

Carbon14 is produced naturally high in the atmosphere and then falls slowly to earth to be absorbed by plants, hence it's use in carbon dating. Mountains by forcing air over the top of them might collect more of this C14 than the ground in general (wind eddies, more precipitation). This same mountainous ground will then receive more precipitation/melting creating runoff which will collect and concentrate in streams and gullies. So the mud at the bottom of the same can contain unusually high levels of the beta emitter C14.

It is definitely true that atmospheric C-14 is produced in atomic bomb tests, and C-14 is a beta emitter. There is fascinating research enabled by using the spike in C-14 caused by atmospheric testing, which fell off after the Limited Test Ban Treaty forbade atmospheric, underwater, and outer space tests, and most nations instead did all nuclear testing underground. See https://en.wikipedia.org/wiki/Bomb_pulse

However, we know the clothing was tested with STS-6 thin metal walled Geiger tubes. These tubes are not sensitive to C-14.

C-14 is actually a problem in labs because Geiger counters can't detect accidental spills. For example, this website discusses safety issues when using C-14. Note the section on detection. https://www.upstate.edu/radiationsafety/procedures/c-14.php

[ash73]

Some superb input there, very interesting.

Did all the clothes that tested positive for radiation belong to (not worn by) Krivonischenko?

[KFinn]

Thank you, all!!  This is helping to give me a better picture!!