Re: [tlug] Measuring radioactivity at TEPCO Fukushima plant

[Kalin KOZHUHAROV <me.kalin@example.com>]

Hi again,

On Sun, Mar 20, 2011 at 20:30, Kalin KOZHUHAROV <me.kalin@example.com> wrote:
> I have been waiting for my friend who is an radiation measurement
> expert to get on-line and been reading about these Bq/kg readings...
>
My guy is out in the field with no net, duh...

So, I actually pulled out the big physics textbooks (>1000pages) and
started calculating myself based on the radioactive decay law.

> Technically it does work, however at the level we are talking about
> especially for Tokyo, I really doubt it. I couldn't get a formula to
> convert Bq/kg from I-131 into mg/kg, but based on my intuition it
> should be even ng/kg. If I am right at interpreting the latest figures
> for Tokyo[1], 2.9Bq/kg from I-131 means that average 2.9 atoms of
> I-131 decay per second inside 1 kg (1 liter) of water. Given the short
> half-life of I-131 (about 8d), I really doubt there is a lot of it.
> Understand that the detector these days are _really_ sensitive!
>
> [1]     http://eq.wide.ad.jp/files/110320water_1300.pdf
>
Based on my calculations and if the math was correct, at the maximum
permissible level for Iodine-131 (300Bq/kg), this will amount to 24
fg/kg (femtograms per kilogram, femto is -15)... As the formula is
proportional, for the Tokyo levels 2.9Bq/kg that gives 2.9/300*24=0.23
fg/kg (or about a million atoms of I-131 in a liter of water :-)

At hose levels, even analytical chemistry is NG... So I think there is
really no concern.

Cheers,
Kalin.