Measuring contamination on clothing - Table 2

[Ryan]

I've seen some misinterpretations of the radiological report (pp. 371-377), so I wanted to walk people through the methodology and the math on Table 2.

The Soviets are using a measurement unit for beta contamination of disintegrations per minute per 150 square centimeters. (This is a bit strange; I've recently acquired American military surplus contamination probes, and they use 100 cm^2 as the area.)

The test equipment is an array of four STS-6 Geiger tubes in a "lead house." People in the US typically use the term "lead castle" - it's just an enclosure shielded on all sides by lead. Because the goal is to count decays from the fabric, anything that can be done to reduce the natural background hitting the Geiger tubes will make the instrument more sensitive to the sample placed inside it due to decreased background noise.

The report mentions the background radiation as being 90 pulses per minute before washing, and 100 pulses per minute after washing. My assumption is that they probably measured all the samples before washing at one time, and all the samples after washing at another time, taking one background reading for each time. Background radiation is not constant. Weather can affect radon concentration, for example. I imagine atmospheric density and the sunspot cycle will have an effect, too. To determine the background number, they simply run the detector with the chamber empty.

Let's look at item #10, Dubinina's brown sweater. Before washing, it measured 640 counts per minute, which appears in the "Total cpm" column. However, 90 is the background number, so we take 640 - 90 = 550 counts per minute.

Now there is an adjustment factor of 8.9 mentioned in the report. A Geiger tube isn't always going to respond with a pulse if a beta particle hits it because it is not 100% sensitive. Also, there are geometry issues. A radioactive sample is going to emit radiation uniformly in all directions. If you have four tubes sitting above the sample, not every particle will strike a tube. So that means not every beta emitted by the sample will be counted. It appears this detector will measure 1 beta for every 8.9 emitted. So we take 550 counts / minute * 8.9 and arrive at 4895 actual disintegrations from the sample. This appears in the report as 4900, clearly rounded, in the "Radioactivity of contaminated area" column.

Next, it must be noted that the sweater sample size was only 75 cm^2 according to the "Area cm^2" column. But the standard for activity is disintegrations per minute per 150 cm^2. So we need to multiply the result by (150 / 75) or 2. And 4895 * 2 = 9790. The report lists 9900 in the "Radioactivity of contaminated area in terms of 150 cm^2" column. Again, rounded. (This is a guess, but I'm wondering if they used a slide rule, in which case the numbers will be close but not exact.)

Looking at the values after washing, we get:

(390 - 100) * 8.9 = 2581 (the report shows 2600)
2581 * (150 / 75) = 5162 (the report shows 5200)

Now I need to note that lines 6 and 7 have typos in the English translation on dyatlovpass.com. They list the counts per minute after washing as 11 and 77, respectively. These make no sense because background after washing is 100. But looking at the report image, I see this is 111 and 177 respectively.)

Samples 2, 3, and 4 list 2 pairs of numbers for total counts per minute. I'm guessing that the before washing and after washing activities may have been measured twice. It seems only the first number was used for further computation, except for sample 4 after washing, in which case the last was used.

Now the number 5000 decays / minute / 150 cm^2 has been used as a threshold in the report. First, I need to be clear that this is NOT background. As shown above, background was subtracted early on. So any number substantially >0 means there is contamination above natural background.

This 5000 number appears to be an occupational safety limit. In other words, if you worked at a Soviet nuclear facility, and at the end of your shift your clothes had 6000 decays per min per 150 cm^2, that would be considered an unacceptable problem.

But that does NOT mean that, say, ending your shift with 4000 on your clothes is in any way normal! It still means your clothing is contaminated. The contamination is just not at a level that would be unacceptable for a nuclear worker. Also, that nuclear worker will not be wearing clothing contaminated at that level home! If there is a potential of contamination, then they're going to change into different clothing for their shift.

But we're talking about hikers in the woods, not workers at a nuclear facility, so anything obviously above 0 is going to be unusual. The fact that many of the results do not exceed the safety standards for a nuclear worker doesn't mean they should be considered normal.

The waistband of Kolevatov's sweater, the bottom part of Kolevatov's trousers, and Dubinina's brown sweater are all >5000. But that doesn't mean they are the only contaminated clothes. All of the 9 samples, before washing, were substantially above background. The least contaminated of the nine samples was the bottom part of Thibault Brignoles' trousers, at 600. Everything else was >1000.

So ALL of the clothing samples tested on ALL four hikers in the ravine was contaminated with beta emitting isotope(s).

[Star man]

I've seen some misinterpretations of the radiological report (pp. 371-377), so I wanted to walk people through the methodology and the math on Table 2.

The Soviets are using a measurement unit for beta contamination of disintegrations per minute per 150 square centimeters. (This is a bit strange; I've recently acquired American military surplus contamination probes, and they use 100 cm^2 as the area.)

The test equipment is an array of four STS-6 Geiger tubes in a "lead house." People in the US typically use the term "lead castle" - it's just an enclosure shielded on all sides by lead. Because the goal is to count decays from the fabric, anything that can be done to reduce the natural background hitting the Geiger tubes will make the instrument more sensitive to the sample placed inside it due to decreased background noise.

The report mentions the background radiation as being 90 pulses per minute before washing, and 100 pulses per minute after washing. My assumption is that they probably measured all the samples before washing at one time, and all the samples after washing at another time, taking one background reading for each time. Background radiation is not constant. Weather can affect radon concentration, for example. I imagine atmospheric density and the sunspot cycle will have an effect, too. To determine the background number, they simply run the detector with the chamber empty.

Let's look at item #10, Dubinina's brown sweater. Before washing, it measured 640 counts per minute, which appears in the "Total cpm" column. However, 90 is the background number, so we take 640 - 90 = 550 counts per minute.

Now there is an adjustment factor of 8.9 mentioned in the report. A Geiger tube isn't always going to respond with a pulse if a beta particle hits it because it is not 100% sensitive. Also, there are geometry issues. A radioactive sample is going to emit radiation uniformly in all directions. If you have four tubes sitting above the sample, not every particle will strike a tube. So that means not every beta emitted by the sample will be counted. It appears this detector will measure 1 beta for every 8.9 emitted. So we take 550 counts / minute * 8.9 and arrive at 4895 actual disintegrations from the sample. This appears in the report as 4900, clearly rounded, in the "Radioactivity of contaminated area" column.

Next, it must be noted that the sweater sample size was only 75 cm^2 according to the "Area cm^2" column. But the standard for activity is disintegrations per minute per 150 cm^2. So we need to multiply the result by (150 / 75) or 2. And 4895 * 2 = 9790. The report lists 9900 in the "Radioactivity of contaminated area in terms of 150 cm^2" column. Again, rounded. (This is a guess, but I'm wondering if they used a slide rule, in which case the numbers will be close but not exact.)

Looking at the values after washing, we get:

(390 - 100) * 8.9 = 2581 (the report shows 2600)
2581 * (150 / 75) = 5162 (the report shows 5200)

Now I need to note that lines 6 and 7 have typos in the English translation on dyatlovpass.com. They list the counts per minute after washing as 11 and 77, respectively. These make no sense because background after washing is 100. But looking at the report image, I see this is 111 and 177 respectively.)

Samples 2, 3, and 4 list 2 pairs of numbers for total counts per minute. I'm guessing that the before washing and after washing activities may have been measured twice. It seems only the first number was used for further computation, except for sample 4 after washing, in which case the last was used.

Now the number 5000 decays / minute / 150 cm^2 has been used as a threshold in the report. First, I need to be clear that this is NOT background. As shown above, background was subtracted early on. So any number substantially >0 means there is contamination above natural background.

This 5000 number appears to be an occupational safety limit. In other words, if you worked at a Soviet nuclear facility, and at the end of your shift your clothes had 6000 decays per min per 150 cm^2, that would be considered an unacceptable problem.

But that does NOT mean that, say, ending your shift with 4000 on your clothes is in any way normal! It still means your clothing is contaminated. The contamination is just not at a level that would be unacceptable for a nuclear worker. Also, that nuclear worker will not be wearing clothing contaminated at that level home! If there is a potential of contamination, then they're going to change into different clothing for their shift.

But we're talking about hikers in the woods, not workers at a nuclear facility, so anything obviously above 0 is going to be unusual. The fact that many of the results do not exceed the safety standards for a nuclear worker doesn't mean they should be considered normal.

The waistband of Kolevatov's sweater, the bottom part of Kolevatov's trousers, and Dubinina's brown sweater are all >5000. But that doesn't mean they are the only contaminated clothes. All of the 9 samples, before washing, were substantially above background. The least contaminated of the nine samples was the bottom part of Thibault Brignoles' trousers, at 600. Everything else was >1000.

So ALL of the clothing samples tested on ALL four hikers in the ravine was contaminated with beta emitting isotope(s).

Thanks Ryan for that detailed analysis.  So from what you are saying all samples taken were contaminated?  Therefore it is reasonable to assume that it is likely that there was widespread contamination on the hikers?

No wonder the military helicopter pilots wanted the bodies in zinc coffins.

[sarapuk]

What we really need to know is what were the READOUTS of the GEIGER COUNTERS used at the site of the Incident  !  ?  All we have, if it is correct, is what Ivanov said ; That the Geiger Counter went crazy around the camp.  Hardly a scientific report, is it  !  ?  Also why only BETA PARTICLES at the Laboratories  !  ? 

[Star man]

What we really need to know is what were the READOUTS of the GEIGER COUNTERS used at the site of the Incident  !  ?  All we have, if it is correct, is what Ivanov said ; That the Geiger Counter went crazy around the camp.  Hardly a scientific report, is it  !  ?  Also why only BETA PARTICLES at the Laboratories  !  ?

I would have thought that if even if they found some evidence of radioactive contamination, then a much more extensive survey of the area and checks of all items would have been carried out. Not just a few clothes samples.  Again it's very strange.

I think Ryan has a good grasp of the technical subject so should be able to shed some light on the case files.

[Ryan]

Thanks Ryan for that detailed analysis.  So from what you are saying all samples taken were contaminated?  Therefore it is reasonable to assume that it is likely that there was widespread contamination on the hikers?

No wonder the military helicopter pilots wanted the bodies in zinc coffins.

Thank you!

Yes, all nine pieces of clothing tested, with at least one piece of clothing from each of the four hikers found in the ravine, was significantly contaminated above background. The level of contamination differed between them, with some being above industrial safety limits and others not, but all were contaminated to some extent.

I'd like to refer you to case file page 370. Ivanov gave all of the four hikers' clothing and some bone / tissue samples to the radiation lab in Sverdlovsk. The report from the lab does not say how the nine clothing samples to test were determined. There may be some sampling bias. I would not necessarily presume the samples are random. It is possible that they scanned all the clothes with a beta sensitive pancake probe and cherry picked the hottest parts to test. But still, the fact remains that all four of the hikers was wearing at least one article of contaminated clothing.

It is a stretch, but I might believe that just one of the hikers in the nuclear industry "brought his work home with him" so to speak, and contaminated his clothes with beta emitters. Even that is a stretch; I see a distinction between protective work clothes that one would wear when handling radioactive substances, everyday clothing that one would wear going to and from the office, and what one would take on a winter expedition in the Urals.

But all four out of four hikers tested having contaminated clothing? No way. No occupational mistakes or sloppy college lab work could explain it. Something happened on the hike or after they died that, at a minimum, contaminated the clothing of all four of the ravine hikers. Period. Paragraph.

As to the helicopter pilot and the demand for zinc coffins (assuming it is true; yes I've seen it on the Internet, but does anyone have an authoritative source citation?), it is a compete and utter overreaction. Unfortunately, the average person has no concept of actual danger regarding radiation. As long as the corpses were wrapped in water tight tarps, there would be no danger at all to the pilot or any future occupants of the helicopter.

[Star man]

Thanks Ryan for that detailed analysis.  So from what you are saying all samples taken were contaminated?  Therefore it is reasonable to assume that it is likely that there was widespread contamination on the hikers?

No wonder the military helicopter pilots wanted the bodies in zinc coffins.

Thank you!

Yes, all nine pieces of clothing tested, with at least one piece of clothing from each of the four hikers found in the ravine, was significantly contaminated above background. The level of contamination differed between them, with some being above industrial safety limits and others not, but all were contaminated to some extent.

I'd like to refer you to case file page 370. Ivanov gave all of the four hikers' clothing and some bone / tissue samples to the radiation lab in Sverdlovsk. The report from the lab does not say how the nine clothing samples to test were determined. There may be some sampling bias. I would not necessarily presume the samples are random. It is possible that they scanned all the clothes with a beta sensitive pancake probe and cherry picked the hottest parts to test. But still, the fact remains that all four of the hikers was wearing at least one article of contaminated clothing.

It is a stretch, but I might believe that just one of the hikers in the nuclear industry "brought his work home with him" so to speak, and contaminated his clothes with beta emitters. Even that is a stretch; I see a distinction between protective work clothes that one would wear when handling radioactive substances, everyday clothing that one would wear going to and from the office, and what one would take on a winter expedition in the Urals.

But all four out of four hikers tested having contaminated clothing? No way. No occupational mistakes or sloppy college lab work could explain it. Something happened on the hike or after they died that, at a minimum, contaminated the clothing of all four of the ravine hikers. Period. Paragraph.

As to the helicopter pilot and the demand for zinc coffins (assuming it is true; yes I've seen it on the Internet, but does anyone have an authoritative source citation?), it is a compete and utter overreaction. Unfortunately, the average person has no concept of actual danger regarding radiation. As long as the corpses were wrapped in water tight tarps, there would be no danger at all to the pilot or any future occupants of the helicopter.

It is also probably the case that some of the clothes samples belonged to Dubinina and Semyon, and we're not borrowed from Krivonishenko and Kolevatov who may have worked with these substances.  It is unlikely that all of the clothing would have been cross contaminated.

Was there any specific results for the bone samples?  I wouldnt expect that much of the radioactivity would have made it into the blood stream through as it would probably get caught in the lungs, and stomach.

Given what they found, why is there no further info or results on other tissues.  Would expect an analysis of the thyroid for Iodine 131?

[Ryan]

I would have thought that if even if they found some evidence of radioactive contamination, then a much more extensive survey of the area and checks of all items would have been carried out. Not just a few clothes samples.  Again it's very strange.

I think Ryan has a good grasp of the technical subject so should be able to shed some light on the case files.

YES YES YES! That lab report raises more questions than it answers.

What about the other five's clothing? What about the tent? The soles of the boots they left behind? And the clothing they weren't wearing, stored in their backpacks? These are quick and easy things to test, assuming the items are still being held as evidence.

Then, I'd want to do a radiological survey of the site where the hikers were found. Is the land itself contaminated, and with what?

I don't know what else, if anything, was checked. Then again, I haven't dug into the source material beyond the radiation report. It's clear from Ivanov's order (p. 370) that Ivanov already knew the clothes were contaminated. How? What kind of radiological inspection had already been made?

But this assumes that the goal is to find the truth. It seems Ivanov was in a hurry to close the case.

Maybe they reached the limits of the resources that could be spent on the case. They found all the bodies. The radiation was not anywhere near enough to be a hazard or a cause of death. None showed obvious signs of being murdered by typical means. There were no suspects to investigate or prosecute. So maybe they had to move on.

And it's also possible that Ivanov was pressured to close the case, and possibly cover something up, hence the reason that further radiological testing may not have been done.

[Monika]

But would he wear the touring jacket and trousers at the work? No. And if he worked with a radioactive material, why only clothes had been contaminated and not his hair and skin?
If it was contamination from work, and as it turned out, this radioactivity is washable with water, it would already be removed during their tour while walking in the snow and during skiing and sitting on the snow at pause break as photos shows. Therefore, the contamination more likely got on clothes in the Dyatlov pass and not before.

[sarapuk]

What we really need to know is what were the READOUTS of the GEIGER COUNTERS used at the site of the Incident  !  ?  All we have, if it is correct, is what Ivanov said ; That the Geiger Counter went crazy around the camp.  Hardly a scientific report, is it  !  ?  Also why only BETA PARTICLES at the Laboratories  !  ?

I would have thought that if even if they found some evidence of radioactive contamination, then a much more extensive survey of the area and checks of all items would have been carried out. Not just a few clothes samples.  Again it's very strange.

I think Ryan has a good grasp of the technical subject so should be able to shed some light on the case files.

According to Ivanov, his Geiger Counter went crazy. And at some point scientists are supposedly involved with their Geiger Counters. If the area was sealed off for some time then maybe there was further Investigations going on  !  ?

[sarapuk]

But would he wear the touring jacket and trousers at the work? No. And if he worked with a radioactive material, why only clothes had been contaminated and not his hair and skin?
If it was contamination from work, and as it turned out, this radioactivity is washable with water, it would already be removed during their tour while walking in the snow and during skiing and sitting on the snow at pause break as photos shows. Therefore, the contamination more likely got on clothes in the Dyatlov pass and not before.

Yes I think most of us are probably thinking along those lines now. Any Radiation Particles are likely to have been picked up in the area of the Dyatlov Groups demise. Even though we are clearly lacking in all the Information, all roads lead to that probability.

[sarapuk]

I would have thought that if even if they found some evidence of radioactive contamination, then a much more extensive survey of the area and checks of all items would have been carried out. Not just a few clothes samples.  Again it's very strange.

I think Ryan has a good grasp of the technical subject so should be able to shed some light on the case files.

YES YES YES! That lab report raises more questions than it answers.

What about the other five's clothing? What about the tent? The soles of the boots they left behind? And the clothing they weren't wearing, stored in their backpacks? These are quick and easy things to test, assuming the items are still being held as evidence.

Then, I'd want to do a radiological survey of the site where the hikers were found. Is the land itself contaminated, and with what?

I don't know what else, if anything, was checked. Then again, I haven't dug into the source material beyond the radiation report. It's clear from Ivanov's order (p. 370) that Ivanov already knew the clothes were contaminated. How? What kind of radiological inspection had already been made?

But this assumes that the goal is to find the truth. It seems Ivanov was in a hurry to close the case.

Maybe they reached the limits of the resources that could be spent on the case. They found all the bodies. The radiation was not anywhere near enough to be a hazard or a cause of death. None showed obvious signs of being murdered by typical means. There were no suspects to investigate or prosecute. So maybe they had to move on.

And it's also possible that Ivanov was pressured to close the case, and possibly cover something up, hence the reason that further radiological testing may not have been done.

There are so many twists and turns in this Dyatlov Case. I and Iam sure many others are glad that you have made this very useful contribution, and keep it up. By digging deeper into the RADIATION aspect we can use the findings to try and make any LINK up with the other areas of Investigation. Some would say its a process of elimination. But with the Dyatlov Case we are dealing with one of the great mysteries of all time. How much do the Authorities still know today  !  ?  How much Information is missing  !  ?  Just getting into the Radiation aspect clearly shows A LOT OF INFORMATION IS MISSING.

[Star man]

What we really need to know is what were the READOUTS of the GEIGER COUNTERS used at the site of the Incident  !  ?  All we have, if it is correct, is what Ivanov said ; That the Geiger Counter went crazy around the camp.  Hardly a scientific report, is it  !  ?  Also why only BETA PARTICLES at the Laboratories  !  ?

I would have thought that if even if they found some evidence of radioactive contamination, then a much more extensive survey of the area and checks of all items would have been carried out. Not just a few clothes samples.  Again it's very strange.

I think Ryan has a good grasp of the technical subject so should be able to shed some light on the case files.

According to Ivanov, his Geiger Counter went crazy. And at some point scientists are supposedly involved with their Geiger Counters. If the area was sealed off for some time then maybe there was further Investigations going on  !  ?

Where in the case files does it say Ivanov Geiger counter went crazy around the camp site.  Don't remember reading that.

[sarapuk]

What we really need to know is what were the READOUTS of the GEIGER COUNTERS used at the site of the Incident  !  ?  All we have, if it is correct, is what Ivanov said ; That the Geiger Counter went crazy around the camp.  Hardly a scientific report, is it  !  ?  Also why only BETA PARTICLES at the Laboratories  !  ?

I would have thought that if even if they found some evidence of radioactive contamination, then a much more extensive survey of the area and checks of all items would have been carried out. Not just a few clothes samples.  Again it's very strange.

I think Ryan has a good grasp of the technical subject so should be able to shed some light on the case files.

According to Ivanov, his Geiger Counter went crazy. And at some point scientists are supposedly involved with their Geiger Counters. If the area was sealed off for some time then maybe there was further Investigations going on  !  ?

Where in the case files does it say Ivanov Geiger counter went crazy around the camp site.  Don't remember reading that.

Apparently in 1990, 'Lev Ivanov', told a small Kazakh newspaper called 'Leninsky Put', in an interview, dug up by The Moscow Times.  As you know this is around about the time when many old records of the goings on in the former USSR started to appear on a regular basis.

[Star man]

What we really need to know is what were the READOUTS of the GEIGER COUNTERS used at the site of the Incident  !  ?  All we have, if it is correct, is what Ivanov said ; That the Geiger Counter went crazy around the camp.  Hardly a scientific report, is it  !  ?  Also why only BETA PARTICLES at the Laboratories  !  ?

I would have thought that if even if they found some evidence of radioactive contamination, then a much more extensive survey of the area and checks of all items would have been carried out. Not just a few clothes samples.  Again it's very strange.

I think Ryan has a good grasp of the technical subject so should be able to shed some light on the case files.

According to Ivanov, his Geiger Counter went crazy. And at some point scientists are supposedly involved with their Geiger Counters. If the area was sealed off for some time then maybe there was further Investigations going on  !  ?

Where in the case files does it say Ivanov Geiger counter went crazy around the camp site.  Don't remember reading that.

Apparently in 1990, 'Lev Ivanov', told a small Kazakh newspaper called 'Leninsky Put', in an interview, dug up by The Moscow Times.  As you know this is around about the time when many old records of the goings on in the former USSR started to appear on a regular basis.

Ok thanks.

Regards

Star man