Re: Nb-97m

["Eric L. Darois" <daroiel@naesco.com>]

     The DAC values in 10CFR20 include contributions from daughters that 
     undergo "ingrowth" after intake.  Since Nb97m has a half life of 1 
     minute compared to its parent (17 hrs), secular equilibrium is reached 
     quickly in the body.  Most of the dose would be derived from ingrowth 
     not from the activity on intake.
     
     Eric Darois, CHP
     daroiel@neasco.com


______________________________ Reply Separator _________________________________
Subject: Nb-97m
Author:  radsafe@romulus.ehs.uiuc.edu at Internet
Date:    11/4/96 9:54 AM


     Does anyone know why risk-based values such as the DAC value in 
     10CFR20 App. B are not present for Nb-97m?  
     
     Nb-97m is a 95% branch between Zr-97 to Nb-97, but does not appear in 
     App. B.  Nb-95m is only a 0.8% branch between Zr-95 and Nb-95, yet it 
     has a table value in App. B.
     
     An isotopic analysis actually identified the 743 keV Nb-97m peak as 
     belonging to Zr-97.  Is Nb-97m risk already included in Zr-97 or Nb-97 
     information?
     
     I would think that the information is covered by either the Zr-97 or 
     Nb-97 values, but I can't prove it with the documentation I have.
     
     
     Glen Vickers
     brzgv@ccmail.ceco.com
     815-458-2801 ext. 2792