Radon222 vs 223 exposure at home

[Ephant]

I read 80% of Radon that can get into the house is from U-238 isotope. But how about Radon 223 (from U-235). Does this comprise the remaining 20% that can get into a house? If it doesn't, then what components are the remaining 20%?

 

[snorkack]

I read 80% of Radon that can get into the house is from U-238 isotope. But how about Radon 223 (from U-235). Does this comprise the remaining 20% that can get into a house? If it doesn't, then what components are the remaining 20%?

Element 86 has 3 main natural isotopes:
Radon (Rn), atomic mass 222, half-life 3,8 days, in uranium series, mother Ra, half-life 1600 years
Thoron (Tn), atomic mass 220, half-life 55 seconds, in thorium series, mother thorium X, half-life 3,6 days
Actinon (An), atomic mass 219, half-life 4 seconds, in actinium series, main mother (it has two mothers!) Ac X, half-life 11 d
Radon 223 (half-life 24 minutes) does not seem to be a significant natural product of actinium series. See a graphic of the series:
https://en.wikipedia.org/wiki/Decay_chain#/media/File:Decay_Chain_of_Actinium.svg
Radon 223 would go to the left of the vertical column between Pa-231 and Bi-215. It would take two alpha decays of Th-231. Actually, U Y does have an α decay branch... to the tune of 10^-8 %! And Ra-227 again is liable to beta decay, half-life 42 minutes, α branch not reported.

 

[Astronuc]

I read 80% of Radon that can get into the house is from U-238 isotope. But how about Radon 223 (from U-235).

The proportions of Rn isotopes will depend on proportions of Th-232 and U-238 in the geological deposit, as well as the decay constants of various intermediaries and the respective Rn isotopes. Also, note that 'natural U' is about 0.72% U-235, although some deposits might be slightly greater.

The Rn from U-235 is Rn-219, with Ra-223 being the precursor. Actinium is a decay product in the U-235 decay series.
Rn from U-238 is Rn-222 and -218, the former having a short half-life (3.8 d) and the latter a very short half-life of 35 ms.
Rn from Th-232 is Rn-220 with a very short half-life of 55.6 s, the precursor being Ra-224.

Ref: http://hyperphysics.phy-astr.gsu.edu/hbase/Nuclear/radser.html
https://www.nndc.bnl.gov/nudat3/

https://www.sciencedirect.com/topics/agricultural-and-biological-sciences/isotopes-of-radon
"The average rate of production of ²²⁰Rn in the ground is about the same as that of ²²²Rn."

The articles emphasize ²²²Rn and the balance apparently being ²²⁰Rn. An article also mentions, "Radon accounts for up to 50% of the total internal dose from all natural background radiation sources and this, in turn, is due almost completely to two of its progeny, namely, polonium-218 and polonium-214, which decay via the release of α-particles. Alpha particles, while lodged in the airways of the lung can damage the cells lining the airways, thus inducing lung cancer." The ²¹⁸Po and ²¹⁴Po are decay products from the ²³⁸U decay series with precursor ²²²Rn.

With respect to "But how about Radon 223 (from U-235)," ²²³Ra is a precursor to ²¹⁹Rn; ²²³Ra is solid so should be in the vicinity of it's production unless it or a precursor is dissolved in groundwater.

 

[Ephant]

So if 80% of Radon at home is the Radon 222. What is the 20% compose of?

And for popular Radon home detectors. Are they really that accurate? For example:

https://www.amazon.com/Corentium-Detector-Airthings-223-Lightweight/dp/B00H2VOSP8/?tag=pfamazon01-20

Initially thought it was supposed to detect Radon 223. But the name is confusing "Radon Detector 223". But then I realised it's just the model. If I get it. Can it detect the Radon in my home?

 

[Vanadium 50]

So if 80% of Radon at home is the Radon 222. What is the 20% compose of?

The articles emphasize 222Rn and the balance apparently being 220Rn.

 

[gleem]

Can it detect the Radon in my home?

Are they really that accurate?

According to the manufacturer of the instrument you referred to, it can. This is a new type of detector optimized for detecting alpha particles and not affected by other types of radiation. Before you buy one check to see if its use is warranted in your area. Here is an EPA map showing areas in the US where one might want to monitor Radon levels.

Regarding accuracy, the manufacturer claims that it can be accurate to ±5% and needs no recalibration. The manufacturer does not tell you that the readings might be affected by high humidity which might occur in a basement. It would have been nice to see a reference to a NIST calibration. You will have to take the word of the manufacturer for its accuracy. The 4 pCi/L action level that the EPA recommends results in a yearly dose of 3.7 mSv if the space is occupied 24/7. So if the area is occupied P% of the time, the resulting dose is P% of 3.7mSv.

 

[difalcojr]

The Rn from U-235 is Rn-219, with Ra-223 being the precursor.

With respect to "But how about Radon 223 (from U-235)," 223Ra is a precursor to 219Rn; 223Ra is solid so should be in the vicinity of it's production unless it or a precursor is dissolved in groundwater.

Just as an aside on this same topic of Rn danger, Rn gas was monitored, daily, by one employee, his only job, throughout one underground W mine in the past. The huge scheelite deposit Inside Mt. Morgan at the end of Pine Creek canyon just north of Bishop, CA. Mine operated 1916-1982; I worked there '80-'82, up until it closed, laying off about 400 employees in the process. Union Carbide.

Smoking wasn't allowed underground (lots of chewing tobacco instead) because it had been determined that smoking and radon gas together are quite lethal. I remember an x-y wall chart from an employee safety meeting, with a horizontal line for non-smokers vs. an exponential curve for smoker deaths. I do not know what those exact Rn levels were at the mine, though.

How many men lost their lives not knowing of this danger through the years, before the alarm had been sounded and testing done? Not sure. This mine was very active during WWII for its tungsten output. The grade runs 1-2% in the scheelite, rich. In one high radon gas area of the mine, you were only allowed to work there two weeks per year. Underground was 42 deg.F. ambient temp. and very wet in many areas, snowmelt percolating through the top of Mt. Morgan into the mountain down inside. Most mining up around 10,000 ft. and higher. Main hoist went1500 feet, taller than the Empire State Bldg. in NYC. From 8100 ft. elevation up to 9600 ft.

There is an abundance of black (smoky) quartz in the eastern Sierra Nevada in certain areas at very high elevations. My understanding is that it is radium that produces this smoky color in quartz. There is no yellowcake or uranium noticeable in the granodiorite, though possibly U 235 in the granitic rock was the main source. Maybe both.

So, now I think It was Radon 223 from Radium 223, and it was released into the air inside the mine due its precursor, Radium 223, was dissolving from the parent rock, or itself, into the water. If I understood you correctly.

 

[Astronuc]

How many men lost their lives not knowing of this danger through the years, before the alarm had been sounded and testing done? Not sure. This mine was very active during WWII for its tungsten output. The grade runs 1-2% in the scheelite, rich. In one high radon gas area of the mine, you were only allowed to work there two weeks per year.

It was not only Rn, a noble gas, but also the decay products, and precursors. The articles I cited discuss additional radiation from ²¹⁸Po and ²¹⁴Po, and perhaps corresponding isotopes of At, Tl, Bi and Pb, which are also toxic heavy metals. Hard rock mining is a very dirty business, and I am certainly aware of conditions in those mines and outside, where tailings were dumped. I've seen too many tailings piles and brownfields.

Fifty years ago, I did a summer student project on assaying the discharge from a U mine in Colorado.

https://www.nrc.gov/info-finder/decommissioning/complex/colorado-legacy-land.html
https://coloradosun.com/2023/12/18/colorado-jefferson-county-uranium-mine-cleanup-failure/

https://www.epa.gov/npdes/use-brownfields-mine-scarred-land-initiative-clean-abandoned-mines

 

[Vanadium 50]

Tailings scare me a lot more than reactor waste. (And low-level waste more than reactor waste as well)

But back to radon - the variation in radon exposure almost falsifies the linear no-threshold model by itself. LNT says radon deaths should be 0-6% depending on geography, and the total cancer deaths run around 12%. We would see a 50% variation in the total cancer rate, which is kind of hard to miss.

However, some homes are more than a factor of 2 - more like a factor 10 or 20 or even more. These are the people who need to take steps.

Which sets the scale for the OPs question on accuracy. You don't need 5% accuracy.

 

[Nik_2213]

If your bedrock mineralogy may produce radon, and it is not being 'vented' by natural faulting or sealed by clay, you must check crawl-spaces and cellars with a reliable device.
IIRC, those potential radon-traps may be sealed with equivalent to a retro-fit damp-course and/or vents fitted to flush residual or accidental ingress, such vents ducted well clear of house openings. Think sewer-line breathers...