Re: SNF Transportation

[RuthWeiner@AOL.COM]

In a message dated 1/14/02 11:02:06 AM Mountain Standard Time, tedrock@CPCUG.ORG writes:



> Wouldn't it make life easier to be able to say that there is no credible situation in which a hazardous amount of radioactive materials could be released?
>
>  


This is only true if by "hazardous" one defines a threshold larger than the A2 values.  EPA defines "credible" (or "foreseeable") as having a probability of one in a million.  We defined it in the Yucca Mountain DEIS as one in ten million, to be sure to capture the considerable uncertainties in our analyses.  There are  very severe, extra-regulatory, foreseeable accidents whose conditional probabilities (conditional on there being an accident) exceed this.  Such accidents almost always involve fire.  One could certainly define a threshold such that the threshold of ceredibility would not be exceeded.


> If spent fuel is cooled for several years before shipping. it is easy to show that there is no mechanism for releasing fission products.  


I refer you to NUREG/CR-6672 (Sprung, et al, 2000) for a contradiction to this statement.  Just for openers:  5-year-cooled PWR SNF is under pressure.  In a hot enough, long enough fire, the package seal can deteriorate and the some PWR assemblies can rupture.  There is then a positive pressure that can sweep out gas (tritium, Kr-85) and volatiles like the cesium and iodine isotopes.  I am not claiming that such an accident is probable, or that the probability exceeds one in a million, but it is certainly possible to postulate this mechanism.


  The cited report is a Sandia report and may be available threough the Sandia transportation risk website. 






Ruth Weiner, Ph. D.

ruthweiner@aol.com