Chernobyl Fallout in USA : One Half-Life Later - Page 1
Forum section: electronics / projects

author: GEOelectronics
author_rank: Regular Contributor
timestamp: July 28, 2019, 08:57:34 pm
content: Cs-137 that is.In 1986 Randall Buck made air samples for a week corresponding to news reports that Chernobyl fallout was due to arrive on the USA west coast. Years later (2012) he sent me the filter paper, which I inserted into a plastic test tube and analyzed in a Bicron 2X2” end well NaI(Tl) probe, in a lead shield. Now it’s 2019 and the date from those tests are being used to show the steps in the process I use to display and analyze very small radioactive samples.A note from Randall concerning details of his sample gathering:“I am the one who took the air particulate sample when I was in Tehachapi CA at an elevation of 4000 ft ASL. I ran a surplus professional air sampler behind my house on an interval timer, one minute every hour , for a week if I remember correctly. I changed paper filters every day and recorded the rise and fall of the total counts per minute as recorded by a Geiger counter. The radioactive plume was predicted to arrive on the west coast of USA so I had time to set up in advance of its arrival. Geo's spectra are the first I have seen since I did not have gamma spec at that time. Randall”A picture tour of my measurements follows, the air sample having been taking in 1986, conveyed to me for Gamma Ray Spectrometry testing in 2013, then the data from those tests reanalyzed in 2019 for this post.The detected Gamma Ray energy scan in keV first in logarithmic display mode, then same data in linear display mode. in most cases, to help show members the advantages of each and which to use in the final display.In the end, the actual amount of Cs-137 present in the sample can be calculated by repeating the setup, taking a similar scan of a known prepared sample of assayed Cs-137 in soil, and comparing the peak reports.George Dowell

author: texaspyro
author_rank: Super Contributor
timestamp: July 29, 2019, 04:46:05 am
content: Back when it happened I was commissioned to design some data loggers with a GPS and radiation detectors. These were strapped to various livestock across Great Britain. I never saw the final results, but the people involved were quite pleased with the results.

author: GEOelectronics
author_rank: Regular Contributor
timestamp: July 29, 2019, 11:44:41 am
content: Quote from: texaspyro on July 29, 2019, 04:46:05 amWould you still have circuits/schematics for those by chance?I've also measured/analyzed mushrooms from a Moscow market, fireplace wood ash from Finland and grass clipping from Fukushima and found Cs-137 in all. Fukushima was really interesting because it also contained shorter lived Cs-134 which I re-analyzer over years and notedthe decrease in Cs-134 while the Cs-137 remained relatively constant.If there is interest in this sort of thing here on EEV, I will be happy to post more survey results and help anyone with equipment advice for setting up electromagnetic electron-Volt measuring gear. It's a fascinating hobbyGeorge Dowell

author: SiliconWizard
author_rank: Super Contributor
timestamp: July 29, 2019, 02:06:10 pm
content: Quote from: texaspyro on July 29, 2019, 04:46:05 amPleased because it worked well, or pleased because the radiation levels were low?

author: Illusionist
author_rank: Regular Contributor
timestamp: July 29, 2019, 03:44:53 pm
content: Quote from: SiliconWizard on July 29, 2019, 02:06:10 pmThat's what I was wondering. I might have eaten some of that licestock...ETA: I left the spelling mistake in because it might be more accurate.

author: GEOelectronics
author_rank: Regular Contributor
timestamp: July 29, 2019, 04:10:23 pm
content: Quote from: Illusionist on July 29, 2019, 03:44:53 pmMy interest is in the science of measuring it, but Cesium- 137 and 134 are man made.Cesium 137 is a product of fission (any fission, bomb and reactor) but Cs-134 is a product of neutron activation (reactor only- the kind with a water pool).Geo

author: texaspyro
author_rank: Super Contributor
timestamp: July 29, 2019, 07:39:20 pm
content: Pleased because they worked well and were very reliable... I don't know anything about the interpretation of the data.I don't have the schematics any more. The detector was a "black box" that sent data over a serial port. A big issue in the design was power management. GPS receivers at the time were rather power hungry and didn't have very good restart times. Also batteries were rather sucky.

author: Vgkid
author_rank: Super Contributor
timestamp: July 29, 2019, 08:09:52 pm
content: This has been an interesting read. Not the Isotope we focus at work(Co-60), and far less sensitive equiptment(but ancient, late 60's/70's gear, with new stuff sprinkled in)

author: MattSR
author_rank: Regular Contributor
timestamp: July 29, 2019, 08:30:59 pm
content: Quote from: GEOelectronics on July 29, 2019, 04:10:23 pmJust to clarify - does that mean that the graphite moderated and water cooled RBMK would not have produced Cs-134?

author: GEOelectronics
author_rank: Regular Contributor
timestamp: July 29, 2019, 09:03:58 pm
content: Quote from: MattSR on July 29, 2019, 08:30:59 pmWhat I know is the majority of Cs-134 is created by neutron absorption by a stable Cs-133 atom, and this takes both time and moderation media. In other words a source of stable cesium,How those conditions might or might not be met in graphite reactors is not something I have studied, but if someone has a scan or a picture of a Gamma Spectrometry done with FRESH fallout from Chernobyl, I could easily figure it out.George Dowell

author: GEOelectronics
author_rank: Regular Contributor
timestamp: July 29, 2019, 09:28:32 pm
content: Quote from: Vgkid on July 29, 2019, 08:09:52 pmCo-60 is really easy to measure it has very unique energies and timing that make it so. It also is a neutron activation product and happens in reactors as well as industrial metrology contexts.What does your work use it for?George Dowell

author: Vgkid
author_rank: Super Contributor
timestamp: July 29, 2019, 09:39:20 pm
content: Quote from: GEOelectronics on July 29, 2019, 09:28:32 pmNaval defense contractor that deals with new construction/overhauling of carriers/subs.

author: GEOelectronics
author_rank: Regular Contributor
timestamp: July 29, 2019, 09:50:08 pm
content: understood vgkid,Yes it occurs especially easily in hi-tech hi-performance metals because they often purposely contain high % stable elemental colbalt.On the other hand all atoms of thorium are naturally radioactive, and thorium is used in high temperature alloys.George