FAQ - RADON - info and measurement

[Richard Hull]

Radon is the direct daughter product of Radium which is itself part of the Uranium decay series.

When the earth was formed, the elemental uranium began to decay and create daughters according the the exponential decay laws governing same. Daughter, by daughter, (there are 14 in all), uranium devolves into stable lead. In theory all earthly uranium can never decay away, but a sizable amount of our seed uranium already has.

Uranium 238, (natural element 92) has a half life of 4.5 billion years. The next longest daughter is Uranium 234 with a half-life of a mere quarter million years.

Equilibrium for each daughter is a term used to describe when the decaying daughter is being replenished as fast as it decays by the parent such that it remains in a constant or fixed amount within the matrix.

For most all older uranium minerals, this equilibrium is nearly met for all uranium daughters. Thus, all the radium that can ever exist within it is there as well as all the Radon, thorium, polonium, protactinium, radio-bismuth and radio-lead. About the only thing that is ever growing is stable lead within it.

Radon is thus, forever pouring out of all uranics in the crust and minerals of the earth. It seeps and rises to the surface via cracks and fissures in the mantle and, ultimately, our soil.

Radon, being a gas, can be breathed in. Unfortunately it has four highly radioactive daughters that all decay through to equilibrium in minutes. All the daughters are solids, (particulates). These solids are Polonium-218, Lead-214, Bismuth-214 and Polonium 214. These can build up in the lungs as the radon that is not exhaled rather immediately decays. Here, the damage is done as all of the subsequent daughters, in turn, irradiate lung tissue and ultimately migrate via the bloodstream to various target organs.

Radon is a bother to anyone having a basement or a house that is not well ventilated or located over a large natural uranium or thorium deposit. Other sources of radon are all man made or man created. Radium in watches, clocks and instruments are a particularly potent source of radon gas and can contribute far more to home radon levels than nature can if present in even modest amounts.

Collectors of meters, clocks and glow in the dark antiques as well as some instruments made prior to 1965 can have a rather significant radon hazard if the materials are stored in the living area. Likewise, mineral collectors with larger Uranium or Thorium mineral holdings can also be at risk if the material is kept within the living space. (thorium emits a much more dangerous "Thoron" gas, which is really just another isotope of radon with a 54 second half life)

These hazards can be easily remediated by simply dropping the offending mineral or watch or instrument in an air-tight container. Sealed polyethylene bags are OK, but a gasketed jar or old military ammo tin with gasket is much better. The other option is to store them outside of a dwelling in a shed or other storage area that is not inhabited.

The government (EPA) has set health limits for Radon gas within an occupied dwelling. The current "no-action suggested" limit is 4 pico curies of Radon/ liter of air sampled within the living space. Between about 4-6pCi/L it is suggested you might take some action to remediate the condition. This can be a simple ventilator system or a multi-thousand dollar house modification!

At or above 8pCi/L it is highly recommended that you take immediate action to reduce the radon levels in the living space. I am unaware of a level set by law where you might be forcibly evicted and your home might be condemned, if not remediated.

Due to anyone of the above conditions, natural or man induced, it is good to know your living space radon levels.

This measurement involves more than a mere geiger counter sweep.

The easiest but less accurate measurment would involve critical area surface wipes and a special alpha counter.

The best method involves direct sampling of the air within the room. Passive air sampling involves a simple activated charcoal container left in a room to collect radon and daughters. This is then closed and mailed to a lab where its alpha count rate from the daughters is taken to arrive at a figure of radon contained in the original air.

Another method is direct and immediate sampling of the air in a special instrument. This method is the one I use at my home and lab and demands a very costly instrument. I was fortunate enough to obtain mine surplus and in superb condition from a friend who tired of the system. I still had to pay a nice chunk of change though.

Setup to measurement - the all important Lucas Cell:

The attached images should be consulted.

The first step is to take a known volume cylinder and coat it all over inside with silver activated zinc sulfide. On one end of the cylinder, place a flat, clear glass window. On the opposite end, attach two hose barbs and valves. This resulting object is refered to as a "lucas cell"

Background counting:

The following assumes that the lucas cell hasn't been used in the past 30 days for radon measurement. This is the time needed to warrant no old radon or daughters contaminates the cell as it would have decayed away to satistical insignificance over this period. (radon half life = 3.85 days)

Place the lucas cell with its glass windowed face mated to an equal diameter photomultiplier tube. Seal in a total darkness type of mounting. Count a full 2 hour background for the cell and record the counts per minute in a record book. (Usually ~2 CPM or less)

Sampling the air:

Remove the cylinder from the PMT mount housing. Attach one hose to a cell barb and run to a suction pump. Place another hose on the other cell barb. Expose the open tube end of this free hose to the air in the room. Open the valves and start the pump. This draws in outside room air to the cylinder while the old cylinder air is pumped out and exhausted. After a few minutes the cylinder's original air is replaced by room air. Turn off the pump and valve off the barbs on the cylinder. Disconnect all hoses. Lay the cylinder aside for about 4 hours to let the radon daughters accumulate. Record this idle interval in the log book.

Now re-attach the cell face window to the PMT via the special dark-mount assembly. Start the sample counting and let it run for several hours. When done, compute the CPM and record next to the background reading in the job log book.

Now, using the time based special tables and equations supplied with the cell and armed with all times, counts per minute, and manufacturers cell constants, plug in the values and determine the pCi/L of your room air. The process usually demands several hours of data collection. Remote locations can be sampled and the cells taken back to the lab or instrument for overnight counting and reduction.

My Pylon System can go anywhere due to internal, rechargable batteries.

Professional radon testing companies in the largest cities can be found in the yellow pages. The Richmond based orgainzation is RadonEase.

http://www.radonease.com

You can view radon levels in Richmond via zip codes. They identify streets within the ZIP where homes have been tested (but not the address) and the tested levels reported. I live at 23228 ZIP. Some nearby levels have hit 38 pCi/L!!! You can bet this is an older home with a basement.

My own testing is done by me about every 6 months. (only because I can and for free)

Here are my results over the last two years. 3.1, 3.3, 2.6, 2.9 ( Note* all readings are in standard pCi/L). These are for my living area, inside my home. I have no basement.

The costs for professional testing can be high or low depending on where you are and what type of tests you choose, but figure on over $100.00

Thoron = Radon-220 is particularly nasty and is not counted in any normal sweep for Radon-222. In Virgina, the uranium soil content is generally rather low, but due to large, extant pegmatite masses, monazite and thus, thorium is the more common radioactive found. Thus, the Thoron danger is always under reported and to my knowledge is unquantified, locally.



Richard Hull

[Richard Hester]

Actually, U235 clocks in with a 1/2 life of 713 million years, wihich is why there is any still around....

[Richard Hull]

U235 is a separate decay chain and is not part of the Uranium U238 decay series. It is normally not considered for radon purposes as it contributes virtually nothing to radon levels due to its tiny fractional presence in earthly uranium.

There are three natural decay series.

The Uranium series starts at U238
The Thorium series starts at Th232
The Actinium series Starts at U235

For a full treament of all of the decay series, check out

http://www.radiochemistry.org/periodict ... es/A2.html

Unfortunately, the most interesting and useful part of the Uranium series following radon is omitted in this nice URL reference.

I will complete them here.

Rn222 via alpha to Po218 - 3 minutes then
Po218 via alpha to Pb214 - 26.8 minutes then
Pb214 via alpha, beta to Bi214 - 19.7 minutes then
Bi214 via beta to Po214 - 160 usec then
Po214 via alpha to Pb210 - 22 years then
Pb210 via beta to Bi210 - 5 days
Bi210 via beta to Po210 - 138 days
Po210 via alpha to Pb206 - stable

There are thosands of different gamma energies scattered over all the series.


Richard Hull

[dabbler]

I've got a sneaking hunch that formaldehyde, isocyanates and ozone
are the big hazards for the majority of us. People living in very tight,
energy efficient homes will have these hazards as well as radon
working on them.

[Richard Hull]

True! Radon is not a big hazard for most of us. It is either dangerous or not dangerous in every home. There is pretty much no middle ground. It is not something that changes much over time.

It seems there is always something that we need to be afraid of. We just can't get comfortable without something to be in fear of, constantly. No reason to fret over running out of fear and paranoia! The media really helps us out here and funnels every new horror, real, perceived, or imagined into our home via the TV. How many pesky little post cold war nasties does it take to equal the duck and cover horror of the commies comin' to get us?

When I was a kid it was the Godless Reds, Polio and Tuberculosis. All three are, effectively, just memories now.

Richard Hull

[JohnCuthbert]

Isocyanates are not much of a problem unless you are spraying polyurethane paint or your house is on fire.

[Tom Dressel]

Check out Aware electronics for continuous monitoring software and hardware http://www.aw-el.com/index.htm

Tom Dressel

[Richard Hull]

Thanks Tom! Aware is a pretty cool resource. Who on this list operates this site? My memory is shot and spiraling down in flames. Please forgive.

Regardless, those with few electronic skills and who have five thumbs on each hand might support AWARE with the favor of their business. (note, I get no kickback here, honest)

Richard Hull

[Adam Szendrey]

I'm playing with the thought of ordering the RM-60 system from them in the next couple months maybe (when i have the money to be exact).
Would cost me 150 $ plus 20 $ shipping. Though i wonder if it's worth the price, and if it's really useful for that money for fusor and other rad. work.
Here are the response graphs:
http://www.aw-el.com/tubegrap.htm

I would appriciate any feedback here from those of you who have experience with this system.
Via activation i can use this detector to check if there were neutrons after a fusor run, right (forgive my under-education on activation, i'm drawing conclusions (good or bad) from what i have learned about it here).
Because then i would not need a separate neutron detector...

Thanks!

[Jon Rosenstiel]

Richard,

Isn't it Chris Smolinski?

Jon Rosenstiel

[Tom Dressel]

Does anyone have any experience with the Aware Electronics devices for monitoring low level background radiation levels.

Tom Dressel

[ChrisSmolinski]

Jon Rosenstiel wrote:
> Richard,
>
> Isn't it Chris Smolinski?

Actually I run Black Cat Systems. Aware's detectors are similar to ours, but I
believe you have to pay extra for their Windows software (almost as much as
their detector).

All the details on our detectors are available at
http://www.blackcatsystems.com/GM/ plus I'd certainly be glad to answer
any specific questions.

Our software lets you auto-upload graphs to your website, take a look at http:
//www.blackcatsystems.com/GM/compare.html which shows two GM-10
units (one outside) and a GM-45 (pancake tube).

The adjustable integration time makes it possible to measure low levels. The
graphs on the above URL have a 15 minute integration period (from memory)
which helps to reduce statistical noise.