Abundance of 727 KeV Line in Bi-212

["Leo M. Lowe" <llowe@senes.ca>]

Hello,



In gamma spectroscopy analysis of samples containing natural thorium 

(Th-232), almost certainly in radioactive equilibrium, the concentration of 

Bi-212 was much lower than expected (i.e. about 60% of the Th-232 

concentration).  The Bi-212 concentration was based on an abundance of 

11.8% (e.g. as given in ICRP 38) for the 727 KeV line.  However, if the 7% 

abundance for this line as given in the Radiological Health Handbook were 

used, the Bi-212 concentration would be much closer to the equilibrium 

concentration (i.e. 7/11.8 = approx. 60%)



A similar ratio (between ICRP 38 and the Radiological Health Handbook) was 

also found for the 1.62 MeV line, with reported abundances of 2.75% and 

1.8%, respectively (i.e. 1.8/2.75 = approx 65%).



What are the "accepted" abundances for the Bi-212 727 KeV and 

1.62MeV  lines?  Has anyone else had this problem?



If more appropriate, please feel free to respond to me directly.  (I get 

Radsafe via Digest mode i.e. only once per day.)



Thanks.

Leo M. Lowe, Ph.D., P.Phys.

Principal, Senior Health and

Environmental Physicist



SENES Consultants Limited

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Richmond Hill, Ontario

Canada L4B 3N4

Tel:	(905) 764-9380

Fax:	(905) 764-9386

llowe@senes.ca

www.senes.ca



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