[ RadSafe ] Fukushima and the Pacific - some calculations

[William Lipton]

You seem to be making the dubious assumptions that:  (1) the radionuclides
mix instantly and uniformly with the Pacific Ocean, and (2) there is no
re-concentration mechanism, such as in fish.

Bill Lipton
It's not about dose, it's about trust.
Curies forever




On Mon, Jan 6, 2014 at 11:28 AM, KARAM, PHILIP <PHILIP.KARAM at nypd.org>wrote:

> OK - so let's do some math!
>
> According to a report put out by PNNL the total radionuclide inventory of
> Units 1 and 3 was about 2.30 x 10^17 Bq about three months (100 days)
> post-shutdown (I will have to post the URL for this report later - can't
> find it at the moment). If we assume that this is for each reactor then the
> total fission product inventory of the three affected reactors is about
> 7x10^17 Bq. This is based on the ORIGEN computer code, although I can't
> remember if it was based on the actual or the worst-case power history for
> these reactors.
>
> The volume of the Pacific Ocean is about 7x10^17 cubic meters (
> http://www.ngdc.noaa.gov/mgg/global/etopo1_ocean_volumes.html). This
> means that if the entire fission product inventory of all three Fukushima
> reactors were to magically dissolve into the Pacific Ocean the average
> activity concentration would be about 1 Bq/cubic meter or about 1 mBq/liter
> (there are 1000 liters per cubic meter).
>
> The concentration of natural radioactivity in seawater is about 12
> Bq/liter (http://www.physics.isu.edu/radinf/natural.htm), primarily K-40.
> This suggests that the worst-case event - complete dissolution of all three
> reactor cores into the Pacific Ocean - would add insignificantly to the
> amount of radioactivity naturally present in the seawater.
>
> If we take this a little further and assume (to make things easy) that ALL
> of the radioactivity is Cs-137 then we can calculate the radiation dose to
> someone immersed in the water. According to Federal Guidance Report 12 (
> http://www.epa.gov/radiation/docs/federal/402-r-93-081.pdf) the dose
> conversion factor for immersion in water containing dissolved Cs-137 is
> about 1.5x10^-20 Sv/sec for every Bq/cubic meter. Doing the unit
> conversions (3.15x10^7 seconds per year) shows us that living continuously
> in water with 1 Bq/cubic meter of Cs-137 would give a radiation dose of
> about 5x10^-13 Sv annually. I'd suggest that this is a radiation dose not
> worth worrying about, and it certainly falls into the category of what the
> ICRP calls a "trivial" dose of radiation. And even if the spent fuel pools
> contain 100 times as much radioactivity as the operating reactors (which is
> almost certainly not the case) the radiation dose is still incredibly low.
>
> This is a VERY quick and dirty calculation that is highly conservative.
> The conservative parts are:
>
> -Assumes the entire fission product inventory dissolves into the seawater
> -Does not account for decay since the 100 day point
> -Assumes continuous exposure to the radionuclide-containing seawater
> -Assumes all of the dose comes from gamma-emitting Cs-137 (as opposed to
> alpha and beta emitters)
>
>
> And, to keep everyone honest, here are the parts of this that are not
> subject to much conjecture:
>
> -Fission product inventory is based on the physics of nuclear fission and
> was calculated by a tried-and-true computer code
> -The Law of Radioactive Decay seems to operate consistently across the
> universe (we can see evidence of this in the spectra of supernovae at great
> distance)
> -The volume of the Pacific Ocean is fairly non-controversial
> -The dose conversion factor for various nuclides is based on energy
> deposition per unit mass and these are also fairly non-controversial
>
> Thus, barring a math mistake (always possible) there shouldn't be much
> argument about the calculated radiation dose. And I know I can count on all
> of you to let me know if I had a keystroke error!
>
> So - barring some freak concentration of radionuclides by a factor of many
> orders of magnitude - there seems to be no plausible mechanism for the
> reactor cores to cause death and destruction across the Pacific. So
> residents of our Pacific Coast states (plus Hawaii) would seem to be safe.
>
> Andy
>
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