[ RadSafe ] Re: Spent Fuel and Decay - Dangerous for Millions ofYears?

[Brennan, Mike (DOH)]

>From the NWMO report:

"The radiotoxicity analysis for used CANDU fuel suggests that this material is a potential internal exposure health risk for more than one million years (Mehta et al. 1991; AECL 1994).  Similar analysis for used pressurized water reactor (PWR) fuel with enriched uranium-
235 suggests that the radiotoxicity of used fuel becomes equal to the equivalent uranium ore
after about 130,000 years (IAEA 2004). Other analysis suggests the time period is between
500,000 and one million years (OECD 2004)."

I am sure I join with everyone on the site to encourage people to not eat neither spent fuel, regardless of age, nor uranium ore.  I will even go so far as to recommend that people not eat ceramic of any sort, or ore no matter what toxic metal might be refined from it.

I submit that any set of assumptions that result in spent nuclear fuel being as available for unintentional ingestion as uranium ore is suspect, and needs very strong justification before being accepted.   

-----Original Message-----
From: radsafe-bounces at radlab.nl [mailto:radsafe-bounces at radlab.nl] On Behalf Of Leo M. Lowe
Sent: Monday, July 30, 2007 6:36 AM
To: radsafe at radlab.nl
Cc: JGinniver at aol.com
Subject: [ RadSafe ] Re: Spent Fuel and Decay - Dangerous for Millions ofYears?

Your point about "dangerous" is well taken.  A simplistic comparison of total activity or dose rates certainly does not give the entire picture of the potential hazards of spent fuel.  A more complete description is required.

However, the purpose of my comment about the dose rate near spent fuel, which perhaps could have been more clearly stated, was to indicate that spent fuel would not necessarily be immediately hazardous for "millions of years" to anyone exposed.  While it would be very radioactive for a long time, the direct doses, such as for example might be encountered if retrieval were required, could be easily handled long before millions of years have past.  Note that the dose rate of 0.82 mSv/h from one spent fuel bundle after 500 years is with no shielding.

>Message: 6
>Date: Fri, 27 Jul 2007 17:39:36 +0200
>From: Peter Bossew <peter.bossew at jrc.it>
>Subject: Re: [ RadSafe ] Re: Spent Fuel and Decay - Dangerous for
>         Millions        of      Years?
>To: radsafe at radlab.nl
>Message-ID: <46AA11B8.7070205 at jrc.it>
>Content-Type: text/plain; charset=ISO-8859-1; format=flowed
>
>A useful document (although 10 y old), I find:
>
>  http://www.senat.fr/rap/o97-612/o97-612_mono.html
>
>A table with inventories can be found in sec. 2.1, Le butoir du césium.
>tMLi = t de métal lourd irradié.
>
>What "dangerous" means, is rather a philosophical question which can 
>hardly be solved by scientific reasoning. Comparing the total 
>activities or dose rates of U ore and spent fuel or reprocessing 
>residues is somewhat problematic, because the compositions are very 
>different, and therefore their behaviour in the environment and the 
>biological efficiencies.
>
>pb
>
>
>
>
>
>Leo M. Lowe wrote:
> > Hello,
> >
> > Further to the on-going discussions on the decay of spent fuel, the 
> > National Waste Management Organization (NWMO), the Canadian 
> > organization responsible for advising on how Canada should manage 
> > it's spent nuclear fuel, gives a graph of the decay of the 
> > radioactivity of CANDU (natural uranium) fuel and a table of the 
> > dose rate around a spent CANDU fuel bundle (see Table A3-3 in NWMO 
> > final report available at http://www.nwmo.ca/ )
> >
> > At 500 years of decay, the dose rate at 0.3 m distance from the 
> > bundle is 0.82 mSv/h.  Therefore, as has been pointed out by others, 
> > a worker could spend up to  7 working days (56 hours) next to the 
> > bundle and still not exceed the 50 mSv/y occupational dose limit for exposure in
> > a single year.   While this is certainly not recommended, and the fuel
> > is still quite "hot', this puts the oft-heard statements about the 
> > spent fuel being dangerous for millions of years in a different 
> > perspective.
> >
> > Regards,
> > Leo Lowe
> >



Leo M. Lowe, Ph.D., P.Phys.

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