Need help with some radiological facts [vanity, help]

01/06/2017 | self

[logi_cal869]

It's a huge discrepancy; just seeking some help in narrowing down the actual figure along with a source (I've expended significant time already and only my exasperation has resulted in this request for help).

Thanks in advance.

[Gadsden1st]

The chair is against the wall.

[dp0622]

The answer is 7 :)

[onedoug]

My doc says radiation is cumulative.

[umgud]

Check these out. You can probably google NORM/TENORM Faq sheets too.

http://www.easysurf.cc/cnver24.htm

http://www.iem-inc.com/information/radioactivity-basics/basic-concepts

[waynesa98]

so is this a question about “new born Potassium-40” or the use as you will, as an alternative to radio carbon dating? it matters in terms of how the community looks at radioactivity.

[Leaning Right]

Many years ago, I was doing a research project that involved the force of sliding friction between a certain two materials in contact. So I went to various sources to look for the accepted data.

I was surprised to see how much the data varied on the exact same two materials. I suspect that was due to each researcher’s estimate of uncertainty. Different estimates of uncertainty would lead to different results. Perhaps that is what you are facing here.

[William Tell]

The lower number you are seeing may well be the specific activity of naturally occurring potassium which would only contain a small fraction of K-40.

[Mount Athos]

William tell gave you the answer. The much lower figure is the amount of radiation from k40 in “natural K”. K40 is only a tiny part of natural K.

The higher figure is for pure k40

[Mount Athos]

http://www.iem-inc.com/information/tools/specific-activities

[KarlInOhio]

The 818 pCi/g amount is for potassium with a natural distribution of stable and radioactive isotopes. The Argonne fact sheet says potassium-40 is 0.012% of natural potassium. Take 818 pCi/g and divide by 0.00012 and you get 6.8 uCi/gram of K-40, which is pretty close to the 7.1 uCi/g you already had, given the number of rounding errors and estimates that are running around.

[doorgunner69]

I was surprised to see how much the data varied on the exact same two materials. I suspect that was due to each researcher’s estimate of uncertainty. Different estimates of uncertainty would lead to different results.

Now you know why mechanical and civil engineers design everything 5X what good enough "should" be.

Thank God electronics are more exact.

[Enlightened1]

Hope this helps.

https://hazmap.nlm.nih.gov/category-details?id=1832&table=copytblagents

[Enlightened1]

This may help you too.

http://www.calrecycle.ca.gov/LEA/Conference/06Conf/Presentation/Day2/Radioactive/Greger/K40Food.pdf

[Enlightened1]

One more link,

http://www.philrutherford.com/Potassium-40_A.pdf

[smokingfrog]

Sorry. That information is need to know. ;)

[ifinnegan]

“Take 818 pCi/g and divide by 0.00012 and you get 6.8 uCi/gram of K-40, which is pretty close to the 7.1 uCi/g you already had...”

The 854 is about 7.1.

[logi_cal869]

Thanks, but that actually references the ANL fact sheet, the crux of the problem.

[logi_cal869]

Thanks, but that and your other link are both sources I alluded to utilizing the noted figures, both without reference.

[logi_cal869]

I think I understand what you’re trying to demonstrate. Yes, the math is academic.

However, if Potassium-40 is 0.012% of ‘naturally-occurring potassium’ - and only Potassium-40 is radioactive - then the 0.0000071 figure is nonsensical, suggesting that ALL natural potassium is radioactive.

The conclusion I came to is that an intern building the fact sheet made a boneheaded math error and represented the total possible radioactivity for 100% of naturally-occurring potassium, rather than the 0.012% figure, which in reality only represents the elemental breakdown, not the percentage of radioactivity.

Either I found an error, or the facts are escaping me still and I’m stuck in a boneheaded brainfart.

This is why I asked for help: I need other source(s) for data for which I’ve been unsuccessful or validation of my conclusion, that the 818 pCi/g figure is correct and that ANL, frankly, goofed.

In fact, the National Research Council source predates the ANL fact sheet by 6 years, published 1999....

https://books.google.com/books?id=xkRCx8DROokC&pg=PA48&lpg=PA48&dq=epa+potassium+40+specific+activity&source=bl&ots=B6MNgjYU3o&sig=ZmRgjfRPXmZhWw6uQsy6lzjh3mE&hl=en&sa=X&ved=0ahUKEwjA2qbxg6_RAhVHllQKHTEHDLcQ6AEITjAJ#v=onepage&q=epa%20potassium%2040%20specific%20activity&f=false

...which just happens to state it matter-of-factly as such:
Potassium-40 is present at 0.0117% by mass in natural potassium, thereby imparting a specific activity of about 30 kBq/kb (800 pCi/g) of potassium.

I can accept a discrepancy of 0.0117% vs. 0.012%, but not 0.0000017 vs. 0.000000000818...