Re: [cdn-nucl-l] Tritium danger underrated, report says

[George Stanford <gstanford@aya.yale.edu>]

Jim:
        
        If you like 2.4 mSv better than 2.7, that's fine by me.  The percentage then is 13% rather than 11%, leaving intact the main point -- a 7,000 Bq/L presence of tritium is inconsequential, if it really does result in an annual dose increment of 0.3 mSv or less.

        See also my separate reply to Jaro's message.

                 Best regards,

                          George                     

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At 01:36 AM 6/15/2007, Rad Sci Health wrote:

Hi George,

It’s the 2.7 mSv that confuses me.  World avg natural background has
usually been reported, by e.g., ICRP and UNSCEAR, as 2.4 mSv (vs. the 3.0
mSv U.S. avg).  Is this just from adding a 0.3 mSv avg man-made
radiation background?  I suppose half of the North American man-made
background makes sense, but I don’t remember seeing it before.

Sorry all for too quickly writing/sending this response/query, making the
various errors.  But especially failing to include the ref’d
Canadian web page.  See:

http://www.science.uottawa.ca/~eih/ch7/7tritium.htm 

Regards, Jim
=========
 
on 6/14/07 11:53 PM, George Stanford at gstanford@aya.yale.edu
wrote:

Hello, Jim:

         The 11% came from me.  As outlined below, I did a rough

calculation to see what the implications of a drinking-water limit of

7,000 Bq/L -- which, according to your numbers, would be 190,000

pCi/L, I guess.  Repeating what I said below, the annual exposure

increment to a person who got all -- and I do mean all -- of his

water intake from a supply containing 7,000 Bq/L of tritium came out

to be about 0.3 mSv, which is 11% of a background exposure of 2.7 mSv/yr.

         If someone could authoritatively do his or her own

determination, I'd be grateful.  I got my answer in a round-about way.

         Thanks.

         By the way, as near as I can figure out, a person's body

burden of K-40 and C-14 is about 110 Bq/kg (about the same as the

~120 Bq/kg for a banana) -- but the average energy per disintegration

is about 50 times higher than the ~7 keV energy of the average beta

particle from H-3.  Thus 50 Bq of H-3 would be equivalent to ~1 Bq of

the K-40/C-14 mix.

George Stanford

Reactor physicist, retired.

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At 07:34 PM 6/14/2007, Rad Sci Health wrote:

Hi Randal,

Where did the "11%" come from?

The EPA limit is 20,000 pCi/L, the "correct" limit of 80,000 pCi/L

DCG value.  And 20,000 pCi/L converts to 740 Bq/L ( 80,000 to 2,960 Bq/L).

And, IIRC, the annual generation of H-3 in the atmosphere is ~38,000

Ci, with a equil of 50M Ci.  This was increased by a factor of about

2,000 from the  hydrogen bomb tests, with the peak in 1963 following

the several U.S. and USSR megaton tests.

Although the "2,00" value isn't in this Canadian article, it shows a

good picture of tritium in Ottawa from before '52 into the '90s.

So obviously, the great increase in cancer since the 50s is due to

the massive increase in the inventory of H-3 in the atmosphere!?

Regards, Jim

=========

On 6/14/07 7:48 PM, Randal Leavitt at randal.leavitt@rogers.com wrote:

George Stanford wrote:

 >

 > The Globe and Mail story says the following:

 > "Canada considers drinking water containing up to 7,000 Becquerels per

 > litre of tritium to be safe. A Becquerel represents one radioactive

 > decay a second.  An Ontario government panel recommended in 1994 that

 > the province set a drinking water limit of 100 Bq/L and then lower it

 > to 20 Bq/L over a five-year period. But the advice . . . wasn't

 > adopted. California recently set a goal of having drinking water

 > contain 15 Bq/L or less, although this isn't a binding regulatory

 > standard."

 >

 >      A back-of-the-envelope calculation (taking into account the low

 > average energy of the tritium beta) indicates that the annual dose to

 > a person whose body's entire water content contained tritium at the

 > 7,000-Bq per litre level would have his annual exposure to ionizing

 > radiation increased by ~0.3 mSv, or some 11%.  If my arithmetic is

 > correct, it would seem that the 7,000-Bq/L criterion is not too high.

 >

 >      Confirmation?  Comments?

 >

 > George Stanford

 > Reactor physicist, retired

And we can conclude that their health would be better as a result?  I

think this is the key point - in this dose range the radiation is good

for you.

How does this 7,000 Becquerels litre of water compare with bananas?

Has anyone ever died as a result of tritium being released into the

environment?  What about taking school buses?

If a young mother wants to think about things that might harm her

children, how far down on the list is tritium?

How do we reframe this discussion to show the general reader that living

with energy and its tritium is something that we like and would like to

share?

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