The Ergosphere
Tuesday, August 05, 2014
 

Innumerate "professionals"

I'm used to seeing nonsense on this heyah in-tar-web thing, but sometimes I stumble across something that strikes me as... special, yeah.  Call it special.

One such type of special is the blogger Stock, who calls his blog Nuke Professional.  His latest post is supposedly about "understanding cesium".

How does he go about understanding it?  He starts "With all the big numbers, scientific notation, various ways of expressing radiation units that the pro-radiation stakeholders use to confuse people...."  The various radiation units are products of history and the essential physics, and scientific notation was invented to make both large and small numbers easier to keep track of and understand.  If the public doesn't follow them, the scientific community isn't at fault:  they recommend that everyone learn some science, and can't be blamed if they don't.

From all appearances, Stock goes out of his way to prove that he doesn't understand big numbers, small numbers, and orders of magnitude.  Take the obfuscatory incredulousness about 4 trillion Bq of Cs-137 supposedly stirred up along with dust at F. Dai'ichi.  He expresses disbelief that the quantity of radio-cesium could be as small as 1.25 grams.  If you were a professional, wouldn't your first question be about the actual concentration of Cs-137 in said dust?

Stock professes to read ENEnews, and my first search on the terms "cesium dust fukushima" turned up an ENEnews page claiming "over 200,000 Bq/kg" in dust from the site.  That's 2.0*105 Bq/kg, for all you evil scientific-notation users out there.
4 trillion Bq becomes 4*1012 Bq in the radiation scientists' secret code.  If we use the arithmetic trick called division, we can do this:
4*1012 Bq dispersed / 2.0*105 Bq/kg dust = 2*107 kg dust dispersed.
That 1.25 grams of Cs-137 appears to have been distributed amongst on the order of twenty MILLION kilograms (twenty thousand metric tons) of dust.  The radioactive material was a very small fraction (about 60 parts per trillion) of a rather large total mass.  And I got all of this from a source that he cites with apparent approval.

Stock writes this:
slightly more than 1/3 of ONE GRAM of cesium 137, deposited across a square mile of land as a smoke or gas, is enough to render that land uninhabitable for decades.
Is that correct?  Cs-137 has an activity of 88 curies per gram, so 1/3 gram (about 29 Ci) per square km is 29 μCi/m² or about 1 million Bq/m².  How much actual radiation would that expose you to?  Let's haul out another virtual envelope:

Assume that a human standing on this contaminated ground covers an area of 1/10 square meter.  Half the radiation goes straight down, half goes straight up.  The beta radiation from Cs-137 is blocked by the soles of the shoes, but all the gamma radiation from the decay of Ba-137m is absorbed.  That's 1 million decays per square meter, times 0.5 going upward, times 1/10 square meter:  50,000 gammas per second absorbed.  The absorbed energy is 5*104 events/sec * 6.62*105 eV/event = 3.31*1010 eV/sec = 5.3*10-9 J/sec = 1.9*10-5 J/hr.  For a body weight of 50 kg, this is an absorbed dose of 0.95 microJoules per kg per hour, or 0.95 μGrays (roughly μSv).

Unless I've slipped a decimal place, that's not even 9 milliSieverts (mSv) per year.  That's less than people in Colorado average from groundshine, cosmic rays, and radon.  If that land was uninhabitable, Colorado is uninhabitable.  Such an assertion is as insane as the claim (made in all apparent seriousness by a certain Canadian who I believe I read lives on disability) that California is a wasteland.

That land would not only be safe to live on; it would be safe at ten times the Cs-137 concentration, or 50.  And were it spiced up to 1000 times, it would not be long before rainwater washed the cesium down through the soil and reduced the surface exposure levels back to something quite tolerable.  That very process is going on right now in Fukushima prefecture; radiation levels are falling much faster than the radioisotopes decay, and areas are being cleared for habitation even at Japan's hypochondriacally low standards for safety.

So, uninhabitable for decades?  I don't think so.  And I'm pondering a Kickstarter campaign to go live in Fukushima prefecture for a year to prove it.  A year of sake, sushi and blogging.  Who could ask for more? 
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