Reply #177: Perhaps you're thinking of another argument

[Confusious]

Secular equilibrium:

In nuclear physics, secular equilibrium is a situation in which the quantity of a radioactive isotope remains constant because its production rate (due, e.g., to decay of a parent isotope) is equal to its decay rate.

http://en.wikipedia.org/wiki/Secular_equilibrium

easy enough, don't see how it applies though. We're not talking about the laboratory, or a pure element.

"the total radioactivity of the top isotopic mixture of an element together with its daughter compounds can't exceed the activity of the top isotopic mixture times the length of the longest decay chain."

I would have to point out this and that, I don't even want to bother. exceed the activity?

"The path from U to Pb can't involve more than 7 or 8 alpha emissions, so I took the activity of natural U and multiplied by 10"

Try 11 alpha, 9 beta minus for U238, which is "natural U."


All together, your post made no sense.