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

[Peter Bossew]

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
> __________________________________________________________________________________________ 
>
>
> Hi Mike,
>
> _______________________________________________________________
> Does anybody know of any calculations as to how long it takes spent fuel
> to decay to the activity level it had before going into the reactor?  I
> realize it is highly dependant on factors such as level of enrichment,
> amount of burn-up, activation of cladding, etc, and breeding of Pu.
> Still I would be interested in knowing what the numbers look like.
>
> From: "Brennan, Mike  (DOH)" <Mike.Brennan at DOH.WA.GOV>
> ____________________________________________________________
>
>
> The World Nuclear Association at 
> http://www.world-nuclear.org/info/inf04.html
> shows a graph of the decay of the radioactivity of spent fuel.  
> Apparently, the total activity of the spent fuel is less than the 
> activity of the original ore before 10,000 years of decay.  An OECD 
> NEA 1996 report (Radioactive Waste Management in Perspective) is cited 
> as the source of the graph.
>
> A similar graph was in an issue of Nuclear News a few years ago, but I 
> can't place the exact volume/date at the moment.
>
> Regards,
>
> Leo M. Lowe, Ph.D., P.Phys.
>
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-- 


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Peter Bossew 

European Commission (EC) 
Joint Research Centre (JRC) 
Institute for Environment and Sustainability (IES) 

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