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| The red line in the map above follows my travel route where I did my the measurements |
My measuring device was equipped with Geiger counter, the Geiger tube used was a sbm-20 series. I used this device since I was curious if the radiation levels in Japan where higher than in my own country (Netherlands).
My curiosity was not only driven by the event of Fukushima, but also Hiroshima due the atomic bombing during the second world war. I wondered if there was still something measurable at this location after all these years.
By the way, the Hiroshima memorial place was really, really impressive, it just gave such a good insight to all the damage such a bomb has done. In my opinion I think it is good for the new, young generation to know how much lives and pain such atomic bombs causes...
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| One of the buildings that are still intact after the bombing. |
Before my trip
Before I've booked my flight tickets to Japan, I was a worried about the radiation due Fukushima. In my country there was a lot of bad news about the power plants. So before booking, I did some research. Since I did not know where Fukushima actually was in Japan, I was surprised to see that it was just less than 250km from the main city Tokyo. I expected that there was a lot more distance. But after looking into more and more information about Fukushima on google, my worries became less. Many sites -and yes, it is difficult to determine the validity of the sites- mentioned that it would be safe in Tokyo and other area's. There was only a relatively small location in Fukushima itself that is not accessible for the public.
Geiger counter
It is not cheap to buy a pre-calibrated Geiger counter. The cheapest one I could fine started at more than 400$. So, since I am an electronics engineer, I gathered information how such a device works and if it would be possible for me to construct such a device - at low cost - by myself. I ended up that there are many types Geiger of tubes to use and the method to read such a device was simple enough for me to construct in just a few days before my trip. I selected the SBM-20 mainly because of it's positive reviews on the internet and also because it's easy availability to order it online.
The only downside is that I could not calibrate my Geiger counter since I do not have the proper instruments for that. So my measurements presented are always relative to my own country. I could measure that in my country the background radiation caused around 30CPM (counts per minute) on the SBM-20. This CPM value corresponds to many other users of the SBM-20 on the internet that have measured background radiation with it.
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| Measured background radiation in Amsterdam, Netherlands. |
Testing
As a testing source I used an old Coleman lantern mantle to see if my geiger counter could detect higher radiation levels. The old Coleman lantern mantles are known that they emit radiation due the presence of Thorium. So I've bought a set Coleman lantern mantle on eBay that was tested to emit 1500~ 3000 CPM.
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| Bought from sciencefare at Ebay |
When testing the source to my geiger counter I indeed ended up measuring values around 3000. See the image below
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| Coleman Lantern mantle test source data |
Below you can see the image of my self constructed beta and gamma radiation measuring device. It includes bluetooth, that added me the ability to use my android phone and see real time the data changing.
Besides radiation, it also logs temperature, barometric pressure, humidity and available light directly to an onboard micro SD card.
The PCB is equipped with an Arduino bootloader, the Arduino software supplies the right PWM pulses for the HV generation. Using a 1giga ohm resistor it has the ability to accurately measure the HV section and regulate if necessarily.
Next in my blog: See the actual readings of my trip! Stay tuned...
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