Sr-90 Ingestion dose conversion factor - RegGuide 1.109 vsFGR-11

[kc10100@i-one.at]

A colleague just pointed out that the adult ingestion dose conversion 

factors for Sr-90 (1.86E-3 mrem/pCi or 5.03E-7 Sv/Bq for "T.Body") 

given in NRC RegGuide 1.109, which are based on Hoenes and Soldat (Age-

Specific Radiation Dose Commitment Factors for a One-Year Chronic 

Intake, NUREG-0172, November 1977), are over an order of magnitude 

higher than those (3.85E-8 Sv/Bq) given in DFINT or FGR 11.  He was 

wondering why that might be the case.  The absorption fraction might be 

different (0.3 vs "max", what ever that was actually taken to be in 

Hoenes and Soldat), or it could be that a chronic intake would yield a 

different dose than a instantanous intake.  Could the intake rate 

(acute vs chronic) make that much of a difference? Could it be that 

this is the difference between a "conservative" and a "best-estimate" 

value? Is the "T.Body" dose factor given in RG1.109 not consistent with 

the e_50 of ICRP 60?  Any light you could shed on this problem would be 

welcomed.  Many thanks 



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