West Coast background monitoring

[Richard Hull]

While I think there is zero to worry about, our west coast folks might have an interesting project to report in the near future should any drift over actually occur from the Japanese event.

It might be prudent and instructive to start taking a single 10 minute background count each day and reduce to a CPM count. You should use a 2" pancake, if possible, and a digital scaler to get a precise count instead of using an analog meter.

I don't think this will go anywhere, but it would be interesting, nonetheless. The reading should be taken outdoors at the same place and at about the same time to be useful. Keep a log of the results and report any interesting findings.

If the reading goes up to any significant degree, it would be cool to get a large shallow aluminum pan like used under hot water heaters and fill it half way with water and put it in the back yard with a screen over it, (No bird droppings). Just let the water evaporate and once it reaches a very low level, maybe one quart or less, transfer and evaporate in a smaller container. Next take a wet napkin folded to a 3X3 patch and wipe around the edge of the pan where the water level shows. Gamma spec this and look for Cs137 or other peaks. Do the same with the one quart evaporant pan when all the water is gone. (Shades of my childhood collecting bomb fallout in Richmond from my bird bath so common to yards in the 50's)

If you guys get nuke stuff raining down, I will be super envious. Free isotopes! Such a deal.

Richard Hull

[Adam Ingle]

Good idea, Richard.

I believe the jet stream is currently passing directly over my part of the country that goes over that area of Japan. I have a RadAlert 100, no 2'' probe unfortunately, but I've also got some graphing software. I'll get everything set-up and run multiple 24 hour averages.

I'll post some graphs and if interesting happens I can also post the hard numbers.

Thanks for the idea!

Adam Ingle

[Steven Sesselmann]

Okay so we have established that radioactivity is a problem in Japan at least..

Can anyone elaborate on what isotopes this pollution is likely to be and why?

Is it the nuclear fuel itself which becomes airborne, or is the activity resulting from neutron activation of other matter?

Steven

[Carl Willis]

Hi Steven,

A BBC press report from several days ago, which I linked in another thread, mentioned radioactive cesium and iodine had been identified. If that report is accurate, then it implies damage to fuel, because these radioelements are fission products formed only in the fuel.

The composition of the releases, if they are mostly fission products, would depend strongly on the source (i.e., recently-irradiated fuel in the reactor core, or older spent fuel in the storage pools) and on the method of release. At Fukushima, the most serious releases appear to be coming from spent fuel inventory in the uncovered fuel pools, brought on by thermal degradation of the fuel's cladding and evaporation of volatiles. This means that some of the longer-lived, more volatile fission products that are deposited closer to the cladding probably dominate, e.g. Cs-134 and Cs-137. Much could be learned about the accident from analysis of the radionuclides in the fallout, but data is slow to reach the public in this accident.

-Carl

[Steven Sesselmann]

Carl,

As I suspected, not much information out there....

It would be interesting to know, how and why radioactive particles become airborne.

In what form is the fuel held?
Is it lumps/rods of metal. or pellets or powder?
If the water around the spent fuel rods dry up, do they get hot enough to melt or burn?

Japanese concrete suppliers must be rubbing their hands

Steven

[John Futter]

Steven
the bother with this is that "U" breaks down into multiple daughters but Cs and I are a real problem as both are gasses at fairly low temperatures. So as a gas they leak into the environment. Cs is the most reactive of the alkaline metals and will grab halogens as quick as a wink so if there is saltspray present CS will displace Na to form CsCl a water soluble salt. But the double banger is that alot that comes out is CSI ceasium iodide another water soluble salt, in this case you get both nuclides together.


The fuel rods are made from U2O which is sintered into pellets that melt approx 3900
These are encased in zircalloy tubes (not sure of melting point- around 1900 i think).
Strontium and technicium are also problems, Strontium will happily replace Calcium so your bones irradiate you from the inside if you injest it and the body uses it for bone formation

[Richard Hull]

As I noted in my original post, I think all this is much ado about nothing, for the U.S. at least. It is not like a bomb fallout issue where a large and almost inconceivably hot amount of fission product inventory is lofted very high into the atmosphere.

Basically, every time to see a steam cloud or H2 explosion cloud valut out of the crippled plant, fission product is moving into the atmosphere with most of it certainly coming down within a smallish area compared to the old A-bomb tests of the 40's, 50's and 60's. This is why I hold out that none of the hot stuff should be crossing the Pacific.

Still, it would be cool to know for sure. Jon Rosenstiel will also run some tests as I called yesterday and egg'd him on a bit. He always does things at a high order of fit and finish.

Richard Hull

[Chris Trent]

I'm not expecting anything to make it to Texas, but I've got my monitoring system hooked up finally. We shall see what there is to see.

Right now the monitor is just a stock Lionel CDV 700, (calibrated to a DU check source) connected to a computer for logging. A scintillation counter is under construction, but it probably won't be ready in time.

Current readings, 9cpm; about 0.015 mR/Hr averaged over the last 12 hours.

[Jon Rosenstiel]

Two pronged approach here at my lab in southern California. First, I've placed my Inspector Alert (2-inch pancake tube) just outside my lab's side door and am collecting its output pulses on my MCA. The MCA is set to MCS mode (Multi-Channel Scaling mode) with a dwell time of 10-minutes and an ADC gain of 4096 channels. With these settings it will be possible to record 10-minute counts continuously for nearly 28-days. (Should be more than enough)! Present count-rate is around 43 cpm.

Secondly, I'm planning to do morning and evening wipes on our glass topped patio table. The wipes will be saved in plastic baggies and checked later for Cs-137 using a 2" x 2" NaI(Tl) detector.

A big thanks goes out to Richard and Frank for nudging me off my duff.

Jon Rosenstiel

[Steven Sesselmann]

John,

Thanks for enlightening me with those facts...

Just one more question that bothers me...

Why are Cs and I not normally listed in the Uranium or Thorium decay chain?

Np-U-Pa-Th-Ac-Ra-Rn-Fr-At-Po-Bi-Pb-Ti-Hg

All of these are much heavier than 137Cs and 123I ?

Steven

[Carl Willis]

Cs-137 and I-131 are fission products, and as such represent only a tiny and undetectable fraction of the natural decay products of uranium (U-238 mostly). The alpha decay branch is far more probable than the spontaneous fission branch.

The fission-product isotopes are formed in reactors in large quantities by neutron-induced fission.

-Carl

[Chris Bradley]

Uranium and Thorium can *either* decay (alpha emitters) *or* fission naturally.

The 'fissioning' may be accelerated by neutrons. U-235 fissions into a distribution of isotopes you can find on; viewtopic.php?f=14&t=6898#p47930 The fission releases more neutrons that then induce more fissions.

[Edward Miller]

I've been thinking about the same thing.

Heres the Berkeley Nuclear Engineering Air Monitoring Page
http://www.nuc.berkeley.edu/UCBAirSampling

Then there's these guys.
http://radiationnetwork.com/

I think it'd be an awesome addition to a personal weather station to log and graph background counts similar to how individuals contribute to http://wundergound.com

So what would be a good geiger that I could run non-stop and log the data to a computer?

[Steven Sesselmann]

Check out Rad software from BlackCat systems with this software you can log the counts and publish the chart to an FTP to a server at regular intervals.

http://www.blackcatsystems.com/RadMap/map.html

Steven

[Jon Rosenstiel]

Ok, my GM setup recorded a sharp increase in the background count rate during the afternoon of the 20th (Sunday)… but I’m kind of suspicious as there were lots of other weather related things going on at the same time. (Re: Gusty winds, sporadic rain, heavy rain). Unfortunately, I had to terminate the count at 5:00 pm because the cardboard sunshield protecting my detector was not faring well in the rain.

The patio table wipes turned up nothing but the usual background peaks. (Pb-214, Bi-214, K-40). I plan to re-run the wipes in a day or two using my HPGe detector, I’ll post results (or lack of same) in a couple of days.

Before I plotted it I was certain the rise in count-rate was related to the drop in pressure, but that doesn't appear to be the case. Hopefully someone here can shed some light on the sharp increase in count-rate.

Note: I did manage to capture close to 2-inches of rain water in a plastic tub… with a bit of luck that may shed some light on this.

Edit 3-22-11: This morning I discovered that the sharp increase in count-rate was due to operator error.

Jon Rosenstiel

[Steven Sesselmann]

James,

To record and count background radiation with a GM counter, I think the RAD software from Blackcatsystems is excellent. It's a free download here;

http://www.blackcatsystems.com/GM/page3.html

If you have your own gamma scintillator the simplest way to do Gamma Spectrometry is with Intune, PRA and a suitable Bias supply.

http://www.beeresearch.com.au/

I have a new improved model coming out in a few days, with inbuilt preamp.

Steven

[I have an association with this product ]

[Frank Sanns]

Jon,

Have you ever seen a rise of background counts in such weather conditions before? From your curves it does not look barometric pressure is the culprit. I assume the wind was out of the west or north west which would exclude any significant radioactive mineral deposits being carried your way.

Based on the small quantities that may have been present it is not totally surprising that the NaI detector did not see anything. There are some possible causes so it is not conclusive until the HPGe results are in. You may get another shot at this in the coming days, depending on the winds, as the reactors are still acting poorly.

It is very interesting that you stopped the test just as you reached the magic 65 cpm number that I had predicted.

Thanks for sharing and we look forward to your results.

Frank Sanns

[Richard Hull]

Remember, The uptick in background could be radioactive xenon or another radioactive inert gas which would not show in a wipe test. It would be ephemeral and not likely to stick around. Only a GM would see this, unless you captured gases. Just a thought.

I have personally held out that reactor Xenon might be the only thing that makes it to the west coast.

Ricahrd Hull

[Jon Rosenstiel]

The sharp increase in count-rate was due to operator error. (An electronics SNAFU I discovered this morning).

Sorry for the misinformation.

Jon Rosenstiel

[John Futter]

Jon
We have seen this at work
As rain starts it washes radon daughters out of the atmosphere giving quite a sharp rise in counts as the rain starts. It does drop back again even if the rain continues

Took quite abit to prove and then of course doing more reading it was well documented by others.

[Jon Rosenstiel]

HPGe gamma spec of patio table wipe turns up iodine-131... cool!

Jon Rosenstiel

[Richard Hull]

Just chatted with Jon and he has another wipe test going on now and just two hours in, he says he is getting a Cs137 peak forming! (more specifics later, I am sure)

Wow!

It must be understood that this is still nothing with a micro amount of something. Zero reason to worry. Jon's instrument is ultra sensistive well beyond even our best people's NaI detectors and spectro materials

At last we know for sure that southern Cal has 131 Iodine in the air. Thanks again Jon!
I assume the GM background remains un-impacted at a statistical level?

Richard Hull

[Carl Willis]

Wow. That's impressive.

I have been running some air-sample tests (since Sunday) here in Albuquerque that have so far failed to turn up anything other than radon/thoron daughters. The apparatus for doing this is a box fan on my roof to which I have been taping paper towels. Albuquerque has had almost no rain (a tiny sprinkle yesterday), but maybe I should wipe a surface and see what shows up.

With regard to Cs-137, it's a little harder to ascribe that to a particular source since so much exists from weapons tests, Chernobyl, etc. on account of the long half life. But the source of I-131 is pretty much unambiguous.

FYI, here's UC Berkeley's latest water sample: http://www.nuc.berkeley.edu/node/1904

They also find Te-132 and its daughter, I-132.

-Carl

[Edward Miller]

Here's another page with individual monitors in Japan.
http://japan.failedrobot.com/

[Frank Sanns]

It is the warmest day of year here by far at 65 F but it is supposed to be snowing by midnight so we have a very strong cold front moving through. I have my beta/gamma probe outside under the eve. My readings are less than 10% different than on any other day. They may not even be higher but without a more rigorous determination, I would say nada here in Pittsburgh but I am collecting a bucket of water. Not much hope in detecting anything with the NaI but I will give it a go in a while when the hail in the bucket melts but before the water freezes tonight.

Frank Sanns