Th-232/Ra-228

[Erik Nielsen <enielsen@antechltd.net>]

I have found that thorium mill tailings of an intermediate age 20-40 years 

have a higher concentration of Th-228 than Th-232.  My supposition is that 

removal of the Th-232 concentrated Ra-228 in the spoils above the Th-232 

concentration.  As the Ra-228 in the spoils decayed the Th-228 would build 

up to an equilibrium that would be above the Th-232 concentration.



Fresh thorium mill tailings would not have this effect as the Ra-228 would 

not have had a chance to ingrow to the Th-228 and the Th-228 would decay 

away until supported by the Ra-228 present.  Much older tailings would have 

the Th-228 close to equilibrium with the Th-232 as the Ra-228 that had been 

concentrated had dropped back to the equilibrium value supported by the 

Th-232 and thus the Th-228 value would decay to the supported equilibrium 

level.





Erik C. Nielsen

Senior Radiochemist



Antech Ltd Waltz Mill Laboratory

P.O. Box 158, Bldg G, M/S 62

Madison, PA 15663



mailto:enielsen@antechltd.net



(V) 724-722-5214

(F) 724-722-5208







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