[ RadSafe ] Re: radiosemantics

Bernard L. Cohen blc+ at pitt.edu
Tue Sep 22 11:05:11 CDT 2009

A minor correction, at least regarding the nuclear physics level: The 
decay of the free neutron is irrelevant. What we call "stable nuclei" 
below mass about 100 will never decay. All nuclei with mass above about 
120 will eventually decay by alpha particle emission or spontaneous fission.

Jerry Cohen wrote:
> Franz, Rick, et al.,
> A few years ago, my colleagues and I became somewhat perplexed over 
> what seemed to be an inordinate public concern regarding handling and 
> disposal of "long-lived "radionuclides. For example, Pu-239, with its 
> half-life of 24,000 years, seemed to present a particularly unique and 
> serious threat. Yet the fear of long-lived radionuclides made no sense 
> because , carried to its extreme, the greatest level fear would be 
> directed toward the stable nuclides that do not decay and will exist 
> forever. Of course, such a fear does not exist, so we wondered why the 
> confusion. We concluded that, at least part of the problem stemmed 
> from the rather oversimplified distinction of radioactive vs. stable 
> materials. To remedy the situation, we recommended a new 
> classification of materials by first eliminating the idea of "stable" 
> elements" (the neutron itself decays, so given enough time everything 
> is unstable). We recommended a new classification as follows: 
> Radioactive (definition:  any nuclide that decays with a half-life < 1 
> million years), Radiopassive (nuclides with half lives > 10E6 and 
> <10E12 years), and radioquescent (half life >10E12 years).
> Apparently, nobody bought the idea, but it still makes sense to me.
> Jerry Cohen
> -

Bernard L. Cohen
Physics Dept., University of Pittsburgh
Pittsburgh, PA 15260
Tel: (412)624-9245  Fax: (412)624-9163
e-mail: blc at pitt.edu  web site: http://www.phyast.pitt.edu/~blc

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