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

[Leo M. Lowe]

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.