Warwalking For Radiation

Can’t find a recently updated survey of radioactivity in your neighborhood? Try [Hunter Long]’s DIY scintillation counter warwalking rig. (Video also embedded below.) What looks like a paint can with a BNC cable leading to an unassuming grey box is actually a complete kit for radiation surveying.

Inside the metal paint can is a scintillation counter, which works by attaching something that produces light when struck by ionizing radiation on the end of a photomultiplier tube, to make even the faintest hits “visible”. And the BNC cable leads to a Raspberry Pi, touch screen, GPS, and the high-voltage converters needed to make the photomultiplier do its thing.

The result is a sensitive radiation detector that logs GPS coordinates and counts per second as [Hunter] takes it out for a stroll. Spoilers: he discovers that some local blacktop is a little bit radioactive, and even finds a real “hot spot”. Who knows what else is out there? With a rig like this, making a radiation map of your local environment is a literal walk in the park.

[Hunter] got his inspiration for the paint-can detector from this old build by [David Prutchi], which used a civil-defense Geiger counter as its source of high voltage. If you don’t have a CD Geiger detector lying around, [Alex Lungu]’s entry into the Hackaday Prize builds a scintillation detector from scratch.

24 thoughts on “Warwalking For Radiation

    1. To take into account the time factor use a real time clock and record the date of the measurement (time stamp), use an ultrasonic distance measurement module or time of flight sensor to record the height. The difference (delta) between GPS positions over time gives you the speed. Good luck, and have fun learning.

  1. Very cool project. I grew up right around there (so if you want to post the coordinates and open source your data that’d be neat!)
    Go check out the area around the old reactor on O-Hill near the school. Solar car uva on google maps returns the location. Spent thousands of hours there growing up for a robotics club and always wondered what was around the general area. Nothing notable on a counter we brought over from school one day.

  2. It’s interesting to note that the background levels of radiation vary on a scale of 100x and more, because most often you see public radiation exposures quoted at a couple millisieverts per year, but obviously if you were to build a house on some of these locations that could change by a very significant margin.

    For example, if the average background radiation dose is 6 mSv and you go to the Fukushima exclusion zone, you’re exposed to around 20 mSv which is the safety limit they use – but that’s only three times the “normal” level. Of course you then get hot spots within that area, but the point is that you already have quite hot spots everywhere around you anyways – especially along lakes and rivers where there’s concentrated sediments from erosion which contain naturally occurring uranium, thorium, and their spontaneous fission products (including trace amounts of plutonium).

    If we were to go by official radiation safety limits, we should start avoiding a whole bunch of places as being too contaminated – or revise the safety standards.

    1. Worked in a synchrotron in undergrad, and we had to leave our badges when we went out to lunch b/c the background radiation would give false positives. That’s how low the levels were.

      My dad (biologist) got called into rad safety one month, with real concern in their faces. He had left his badge in a souvenir ashtray from the desert SW, with a bit of yellow paint. Yup, uranium. He’d had the ashtray on his office for years…

      I’m not sure that there are any lessons from these stories, mind you. I think we’re getting dosed all the time. I also think you should avoid as much as you can.

      1. The thing is, human cells have evolved with radiation around and they’re constantly repairing DNA damage caused by ionizing radiation. DNA itself has redundancy where each “word” of genetic information consists of three pairs, and breaking any one won’t change the meaning of the codon, so when a new copy is made it returns back to the original. There is of course a probability of a copying error, but then you have apoptosis that kills the cell before it turns cancerous, and if it does then there’s white blood cells that kill the cancer cells, and if that fails then it depends on what the damage was and whether the faulty cells are too damaged to multiply… there’s multiple redundancies that are all evolved to deal with the fact that cells go wrong all the time.

        The old Linear-No-Threshold model of radiation safety assumes that every effective Joule of radiation absorbed causes a cumulative effect that stays with you for life, which is why you have these safety limits like 20 mSv per year for nuclear exclusion zones. In reality, low levels of radiation is kinda like chinese water torture – the drops don’t harm you, it’s the idea that does. Vastly more harm is done by spreading hysteria about radiation than the actual radiation.

    2. Yeah, that has surprised me as well. I originally built this with the intent of finding man made sources of radiation. I thought I would just see a lot of nothing and then if I ever drove by a long lost fuel pellet or something I would see this spike in radiation levels. However I quickly realized that the natural levels varied wildly everywhere! At first I even thought the probe wasn’t working correctly because of this. But I realized after days of taking data that it was in fact very repeatable.

    1. I was thinking a website like everytrail.com would be nice place to log rad readings for public viewing.
      But when I searched for “GPS trails” yesterday, dozens of similar sites popped up!

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