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Name: Bec S.
Status: student
Age: 15
Location: N/A
Country: N/A
Date: 4/9/2003


Question:
Does uranium238 have the longest half life of all radioactive elements?


Replies:
Oh my, no. U-238's half-life is long, 4.51e9 y, but it is not the longest. Here is a list of nuclides with longer half-lives.
V-50 6e15 y
Rb-87 5e11 y
Zr-96 >3.6e17 y
Te-123 1.2e13 y
Nd-144 5e15 y
Sm-147 1.06e11 y
Sm-148 1.2e13 y
Sm-149 4e14 y
Gd-152 1.1e14 y
Lu-176 3e10 y
Hf-174 2.0e15 y
Ta-180 >1e13 y
Re-187 7e10 y
Pt-190 6e11 y
Pt-192 1e15 y
Th-232 1.41e10 y

The longest-lived of these is Zr-96, with a half-life nearly a hundred million times longer than U-238.

Richard E. Barrans Jr., Ph.D.
PG Research Foundation, Darien, Illinois


U(238) has a long half life but not THE LONGEST. Some other grandfathers are:

Th(232) t1/2 = 1.405x10^10 years,
Lu(176) t1/2 = 3.78x10^10 years,
Hf(174) t1/2 = 2x10^15 years

I am not sure these are the longest, but you can scan the following web site for data in many forms:

http://ie.lbl.gov/education/isotopes.htm

Vince Calder



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