[ RadSafe ] Fukushima and the Pacific - some calculations

Mon Jan 6 11:18:10 CST 2014

Correct. In reality the radioactivity will not mix instantly and uniformly, but by the time it reaches the West Coast it will be fairly well-mixed with the seawater. With regards to concentration in the food chain, the purpose was to look at the scenario trumpeted by Caldicott and others that the West Coast will become uninhabitable, not to perform a rigorous assessment of the food chain (Bruce Napier is much better at that than I am).

Assuming uniform mixing (and the 100-day fission product inventory, as opposed to the current 1000-day inventory) we have a dose that is a fraction of a pSv annually. For this to become biologically significant (say 1 mSv annually for the sake of argument) we'd have to concentrate the radioactivity by a factor of about ten billion. With that sort of a safety factor I feel comfortable with making these simplifying assumptions.

Andy

-----Original Message-----
From: radsafe-bounces at health.phys.iit.edu [mailto:radsafe-bounces at health.phys.iit.edu] On Behalf Of William Lipton
Sent: Monday, January 06, 2014 12:08 PM
To: The International Radiation Protection (Health Physics) Mailing List
Subject: Re: [ RadSafe ] Fukushima and the Pacific - some calculations

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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