Half Life of Po-218 (Radium A)

[john_takala@cameco.com]

     I was recently looking up decay information for radon progeny on the 
     National Nuclear Data Center's web program NuDat.  To my surprise it 
     listed the half life of Po-218 as 3.11 minutes.  
     
     The value that I have commonly seen used is 3.05 minutes (e.g., Table 
     of Isotopes - 7th edition, ICRP 38).  This is a change of nearly 2%! 
     
     Does anyone have any comments on the revised half life of Po-218? What 
     is the reference for it?
     
     
     John Takala