[ RadSafe ] Re: Spent Fuel and Decay

[JGinniver at aol.com]

A quick look on google came up witha report from the Nuclear Waste  
Management Organisation (of Canada)
 
_http://www.nwmo.ca/adx/asp/adxGetMedia.asp?DocID=1487,20,1,Documents&MediaID=
2703&Filename=NWMO_Final_Study_Nov_2005_E.pdf_ 
(http://www.nwmo.ca/adx/asp/adxGetMedia.asp?DocID=1487,20,1,Documents&MediaID=2703&Filename=NWMO_Final_Study_
Nov_2005_E.pdf) 
 
This states that:
 
SNIP>The radioactivity of used [CANDU] fuel decreases to about 1% of  it's 
initial value after 1 year, 0.1% after 10 years and 0.01% after 100 years  (AECL 
1994).  After approximately one million years, the radioactivity in  used 
fuel approaches that of Natural Uranium (AECL 1994; NWMO 2003; Mc Murray et  al 
2003)<SNIP
 
and that
 
SNIP> Radiotoxicityt must also be considered.  Note that the  radiotoxicity 
of used fuel also becomes comparable to that of Natural Uranium  ore on a one 
million year time frame<SNIP
 
and also
 
SNIP> Similar analysis for used PWR fuel with enriched U-235 suggests  that 
teh radiotoxicity of used [PWR] fuel becomes equal to the equivalent  uranium 
ore after about 130,000 years (IAEA 2004).  Other analysis sugests  the time 
period is between 500,000 and one million years (OECD 2004).
 
The refrences were given as :
IAEA 2004, Implications of partitioning and transmutation in Radioactive  
Waste Management IAEA Technical Report Series No. 435
 
OECD 2004, The handling of timescales in Assessing Post Closure  Safety.  NEA 
Report NEA No. 4435, ISBN 92-64-02161-2
 
Mc Murray J, D.A. Dixon, J. D. Garromi, B.M. Ikeda, S. Stroes-Gascoyne, P.  
Baumgarter & T.W. Melnyk 2003.  Evolution of a Canadian deep Geologic  
repositry - Base Scenario, AECL, OPG Nuclear Waste Management Division rep  
06819-REP-01200-10092-R00
 
Regards,
        Julia