Friday, December 27, 2013

Radioactive beach in San Francisco because of Fukushima? Probably not

This guy takes his Geiger Counter to the beach he normally frequents, and shows us "high" radiation readings.  And then he claims it's because of Fukushima.  However, carefully thinking about the video we see he's not demonstrating radioactivity in the water, but in the beach sand.

That is, he starts on a bluff above the beach where readings start at 90ish counts per minute, then by the time he is in the mid-section of the beach it rises to 150ish counts per minute, and then drops to 60ish counts per minute at the water.  He walks back and forth across the beach several times and the same pattern repeats.

If this were radiation from Fukushima, wouldn't the water be reading as hot?

I did some yahoogling and found that beach sands often have naturally occurring radiation.  This is from a mineral known as Monazite, which is a highly insoluble rare earth mineral that occurs in beach sand together with the mineral ilmenite, which gives the sands a characteristic color. The principal radionuclides in monazite are from the 232Th series, but there is also some uranium its progeny, 226Ra.  In most cases the dosage is small/minor, but for a few beaches it is major.  See

Another set of issues are raised by commentors on the YouTube page:
  • the only way to tell if this is from Fukushima is to do an isotope analysis to determine origin. the reading is high, but it could be other stuff causing this, even from nearby. It would be great if someone with the ability to determine the isotope data could please test this area....
  • You rather stop panicking and turn brains on. CPM (counts per minute) counts ionization events only. It does not tell anything in regards to radiation level or dose. Besides, radiation may be alpha, beta, gamma and all are different in their impact on humans. If you put a Geiger-Mueller counter next to a wrist watch you will also get CPM counts :)
  • Ok he peaked at around 150 CPM (air line pilots/flight crew and medical staff get almost twice that exposure daily for hours at a time.)  most professional work environments (outside of office buildings) is 150 cpm a day... which is not dangerous at all, ever had and Xray, well stand on that beach for a few years and you will receive the same dose of radiation.  120 CPM is 1 uSv/hr (microSievert per hour) and 12.5 uSv/hr is considered the threshold for the slightest increased cancer risk or bodily harm... so 12 times more CPM on that beach is needed if you want to be concerned.  Science, it will calm your fears.
In other words - he counted radiation events, but without knowing what kind of radiation it is.

I've been doing some research into geiger counters.  The SE Inspector shown here is one of the better varieties because it has a large geiger-meuller tube, making it more sensitive than the cheaper geiger counters.

But if the person walking around with the geiger counter doesn't know how to interpret the data all bets are off about the usefulness of information that results.  Says the person who knows very little about geiger counters, and just bought one, and may be posting some clueless video in a few weeks.

By the way - yes, this geiger counter is sounding an alarm.  On this device the threshold where the alarm goes off is configured by the user.  You hear him clearly say he set the alarm at 3x what he determined to be "background".  And we see in the video that the alarm sounds every time it went above 100 counts per minute.  Therefore, the alarm isn't something the manufacturer decided was dangerous, but what the guy who owns this thing thought was dangerous.

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